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1
Varley, Denise Joyce. "Novel inhibitors of glutamine synthase." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308650.
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Olomola, Temitope Oloruntoba. "Synthesis and evaluation of novel HIV-1 enzyme inhibitors." Thesis, Rhodes University, 2011. http://hdl.handle.net/10962/d1005034.
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This study has involved the design, synthesis and evaluation of novel HIV-1 enzyme inhibitors accessed by synthetic elaboration of Baylis-Hillman adducts. Several series of complex coumarin-AZT and cinnamate ester-AZT conjugates have been prepared, in high yields, by exploiting the click reaction between appropriate Baylis-Hillman derived precursors and azidothymidine (AZT), all of which have been fully characterised using spectroscopic techniques. These conjugates, designed as potential dual-action HIV-1 inhibitors, were tested against the appropriate HIV-1 enzymes, i.e. HIV-1 reverse transcriptase and protease or HIV-1 reverse transcriptase and integrase. A number of the ligands have exhibited % inhibition levels and IC50 values comparable to drugs in clinical use, permitting their identification as lead compounds for the development of novel dual-action inhibitors. In silico docking of selected ligands into the active sites of the respective enzymes has provided useful insight into binding conformations and potential hydrogen-bonding interactions with active-site amino acid residues. A series of furocoumarin carboxamide derivatives have been synthesised in four steps starting from resorcinol and these compounds have also been tested for HIV-1 integrase inhibition activity. The structures of unexpected products isolated from Aza-Baylis-Hillman reactions of N-tosylaldimines have been elucidated by spectroscopic analysis, and confirmed by single crystal X-ray analysis. A mechanism for what appears to be an unprecedented transformation has been proposed. Microwave-assisted SeO₂ oxidation of Baylis-Hillman-derived 3-methylcoumarins has provided convenient and efficient access to coumarin-3-carbaldehydes, and a pilot study has revealed the potential of these coumarin-3-carbaldehydes as scaffolds for the construction of tricyclic compounds. The HCl-catalysed reaction of tert-butyl acrylate derived Baylis-Hillman adducts has been shown to afford 3-(chloromethyl)coumarins and α-(chloromethyl)cinnamic acids, the Zstereochemistry of the latter being established by X-ray crystallography. ¹H NMR-based experimental kinetic and DFT-level theoretical studies have been undertaken to establish the reaction sequence and other mechanistic details. Base-catalysed cyclisation on the other hand, has been shown to afford 2H-chromene rather than coumarin derivatives.
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Capicciotti, Chantelle. "The Rational Design of Potent Ice Recrystallization Inhibitors for Use as Novel Cryoprotectants." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30634.
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The development of effective methods to cryopreserve precious cell types has had tremendous impact on regenerative and transfusion medicine. Hematopoietic stem cell (HSC) transplants from cryopreserved umbilical cord blood (UCB) have been used for regenerative medicine therapies to treat conditions including hematological cancers and immodeficiencies. Red blood cell (RBC) cryopreservation in blood banks extends RBC storage time from 42 days (for
hypothermic storage) to 10 years and can overcome shortages in blood supplies from the high demand of RBC transfusions. Currently, the most commonly utilized cryoprotectants are 10%
dimethyl sulfoxide (DMSO) for UCB and 40% glycerol for RBCs. DMSO is significantly toxic
both to cells and patients upon its infusion. Glycerol must be removed to <1% post-thaw using
complicated, time consuming and expensive deglycerolization procedures prior to transfusion to prevent intravascular hemolysis. Thus, there is an urgent need for improvements in
cryopreservation processes to reduce/eliminate the use of DMSO and glycerol.
Ice recrystallization during cryopreservation is a significant contributor to cellular injury and
reduced cell viability. Compounds capable of inhibiting this process are thus highly desirable as novel cryoprotectants to mitigate this damage. The first compounds discovered that were ice recrystallization inhibitors were the biological antifreezes (BAs), consisting of antifreeze proteins and glycoproteins (AFPs and AFGPs). As such, BAs have been explored as potential cryoprotectants, however this has been met with limited success. The thermal hysteresis (TH)activity and ice binding capabilities associated with these compounds can facilitate cellular damage, especially at the temperatures associated with cryopreservation. Consequently,
compounds that possess “custom-tailored” antifreeze activity, meaning they exhibit the potent ice recrystallization inhibition (IRI) activity without the ability to bind to ice or exhibit TH activity,are highly desirable for potential use in cryopreservation.
This thesis focuses on the rational design of potent ice recrystallization inhibitors and on
elucidating important key structural motifs that are essential for potent IRI activity. While
particular emphasis in on the development of small molecule IRIs, exploration into structural
features that influence the IRI of natural and synthetic BAs and BA analogues is also described as these are some of the most potent inhibitors known to date. Furthermore, this thesis also
investigates the use of small molecule IRIs for the cryopreservation of various different cell types to ascertain their potential as novel cryoprotectants to improve upon current cryopreservation protocols, in particular those used for the long-term storage of blood and blood products.
Through structure-function studies the influence of (glyco)peptide length, glycosylation and
solution structure for the IRI activity of synthetic AFGPs and their analogues is described. This thesis also explores the relationship between IRI, TH and cryopreservation ability of natural
AFGPs, AFPs and mutants of AFPs. While these results further demonstrated that BAs are
ineffective as cryoprotectants, it revealed the potential influence of ice crystal shape and growth progression on cell survival during cryopreservation.
One of the most significant results of this thesis is the discovery of alkyl- and phenolicglycosides as the first small molecule ice recrystallization inhibitors. Prior to this discovery, all reported small molecules exhibited only a weak to moderate ability to inhibit ice recrystallization.
To understand how these novel small molecules inhibit this process, structure-function studies
were conducted on highly IRI active molecules. These results indicated that key structural
features, including the configuration of carbons bearing hydroxyl groups and the configuration of
the anomeric center bearing the aglycone, are crucial for potent activity. Furthermore, studies on the phenolic-glycosides determined that the presence of specific substituents and their position on the aryl ring could result in potent activity. Moreover, these studies underscored the sensitivity of IRI activity to structural modifications as simply altering a single atom or functional group on this substituent could be detrimental for activity.
Finally, various IRI active small molecules were explored for their cryopreservation potential
with different cell types including a human liver cell line (HepG2), HSCs obtained from human
UCB, and RBCs obtained from human peripheral blood. A number of phenolic-glycosides were
found to be effective cryo-additives for RBC freezing with significantly reduced glycerol
concentrations (less than 15%). This is highly significant as it could drastically decrease the
deglycerolization processing times that are required when RBCs are cryopreserved with 40%
glycerol. Furthermore, it demonstrates the potential for IRI active small molecules as novel
cryoprotectants that can improve upon current cryopreservation protocols that are limited in terms of the commonly used cryoprotectants, DMSO and glycerol.
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Ekici, Ozlem Dogan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5333.
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Takeuchi, Toshihiko Gray Harry B. Goddard William A. Meade Thomas J. "The electronic structure of distorted porphyins and cobalt schiff base derivatives as novel enzyme inhibitors." Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechTHESIS:11052009-085123252.
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Thesis (Ph. D.)--California Institute of Technology, 1996. UM #9617425.<br>Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 01/19/2010. Includes bibliographical references.
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Wiencek, Patrick. "Secondary Functions And Novel Inhibitors Of Aminoacyl-Trna Synthetases." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/941.
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The aminoacyl-tRNA synthetases are a family of enzymes involved in the process of translation, more specifically, ligating amino acids to their cognate tRNA molecules. Recent evidence suggests that aminoacyl-tRNA synthetases are capable of aminoacylating proteins, some of which are involved in the autophagy pathway. Here, we test the conditions under which E. coli and human threonyl-tRNA synthetases, as well as hisidyl-tRNA synthetase aminoacylate themselves. These reactions are ATP dependent, stimulated by Mg2+, and are inhibited by increasing cognate tRNA concentrations. These data represent the foundation for future aminoacylation experiments, specifically delving into the relationship between the autophagy pathway and the aminoacylation of proteins.
Additionally, we provide evidence of the inhibitory abilities of the compound EHTS-0 on both E. coli and human threonyl-tRNA synthetases. Further, we also show that an EHTS-0 analog, EHTS-1, also significantly inhibits E. coli threonyl-tRNA synthetase but not the human enzyme. These data could be useful in determining the potential for EHTS-0 and EHTS-1 as possibly anti-angiogenic drugs.
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Boulton, Sallyanne. "Biological effects of novel poly (adenosine diphosphate ribose) polymerase inhibitors." Thesis, University of Newcastle Upon Tyne, 1995. http://hdl.handle.net/10443/1004.
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Poly(ADP-ribose) polymerase (PADPRP) is a nuclear enzyme with a well documented role in DNA repair. Inhibitors of PADPRP, (e.g. 3' substituted benzamides) potentiate the cytotoxicity of a wide range of antitumour drugs. The results presented in this thesis represent, to the best of my knowledge, the first comprehensive and quantitative assessment of the ability of a range of P ADPRP inhibitors to modulate the cellular responses to damaging agents. Two novel PADPRP inhibitors, 8-hydroxy-2-methyl quinazolin-4(3H)-one (NU1025) and 3,4 dihydro-5-methoxyisoquinolin-1-(2H)-one (PD 128763) were compared with two "classical" PADPRP inhibitors, 3-aminobenzamide (3AB) and benzamide (BZ). The relative potencies for 3AB, BZ, NU1025 and PD 128763 as PADPRP inhibitors in vitro were 1.0, ~1.0, ~43 and ~53 respectively. All compounds potentiated the growth inhibition and cytotoxicity of the monofunctional alkylating agent temozolomide (TM) in L1210 cells. For example, 10/-lM NUI025 and PD 128763 gave dose enhancement factors (DEF) of ~2 at 100/0 survival, whereas ImM 3AB and 0.5mM BZ where required to give similar DEF values. Cellular NADl- levels were depleted up to 50% by 1-2mM TM and this depletion was completely prevented by coincubation with 50-100µM PD 128763 and 1-3mM 3AB. TM induced DNA single strand break levels were increased in a concentration dependent manner by the P ADPRP inhibitors. Overall, the relative potencies for ability of the compounds to potentiate TM induced growth inhibition, cytotoxicity and DNA single strand breaks showed good correlation with those determined in an in vitro inhibition study, with both NU1025 and PD 128763 exhibiting ~60 fold increased inhibitory activity as compared to 3AB. The PADPRP inhibitors per se did not effect the growth or survival of the L 121 0 cells, nor increase DNA strand breakage. NAD+ is the substrate for PADPRP. A L1210 cell line made resistant to tiazofurin (TZ) utilising a step wise selection protocol was shown to be deficient in nicotinamide mononucleotide adenyl transferase (NMNAT) , the final enzyme required for NAD+ biosynthesis. The consequences of a reduced NMNAT activity (<3% of the parental line ) and an ~40% reduction in intracellular NAD+ levels were determined. The resistant cells showed an ~3 fold increased sensitivity to TM as compared to the parental cells. Upon coincubation with increasing concentrations of NU1025 in the presence of a fixed concentration of TM, growth inhibition was potentiated ~70 fold in the resistant cells but only ~10 fold in the parental cell line, demonstrating the reduced level of competition between NAD+ and NUI025 for PADPRP. However, DNA single strand breaks were increased in the resistant compared to the parental cell line only when NU1025 was coincubated with TM. In contrast, in the presence of the PADPRP inhibitors alone, equivalent growth inhibitory effects were observed in each of the cell lines, suggesting inhibition of PADPRP was not the cytotoxic effector. The ~40% NAD+ depletion observed could therefore suggest, that NAD+ levels in the resistant cells were reduced to, or near to the KmNAD+ for PADPRP.
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PRENCIPE, Filippo. "Synthesis and biological evaluation in vitro and in vivo of novel potent anticancer agents affecting tubulin polymerization." Doctoral thesis, Università degli studi di Ferrara, 2017. http://hdl.handle.net/11392/2487939.
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L’attività di ricerca svolta durante i tre anni di dottorato ha avuto come obiettivo la progettazione, la sintesi e l’ottimizzazione di nuovi potenziali agenti antitumorali dotati di attività antiproliferativa e antivascolare che hanno come target biologico i microtubuli, strutture dinamiche cellulari generate dalla polimerizzazione di eterodimeri di α,β tubulina.
Il sistema di microtubuli è essenziale per la divisione cellulare, essendo coinvolto nella formazione del fuso mitotico, ed è importante per diversi processi cellulari quali la regolazione della motilità, segnalazione cellulare, secrezione e trasporto intracellulare.
Tra le molecole di derivazione naturale, il cis-stilbene Combretastatina A-4 (CA-4), legando la tubulina a livello del sito di legame della colchicina, ne inibisce la polimerizzazione mostrando una potente attività antiproliferativa contro diverse linee cellulari tumorali.
L’attività di ricerca relativa al primo anno di dottorato ha riguardato la sintesi di una nuova serie di composti a struttura 1-(3',4',5' trimetossibenzoil)-3-arilamino-5-amino-1,2,4-triazolica per i quali si è andati a valutare l’attività antiproliferativa in vitro, l’interazione con la tubulina e gli effetti prodotti sul ciclo cellulare. Per il derivato più attivo della serie, 1-(3,4,5-trimetossibenzoil)-3-(p-toluidino)-5-ammino-1,2,4-triazolo 3c è stata valutata l’attività antitumorale in vivo. I migliori risultati in termini di inibizione della proliferazione di linnee cellulari tumorali sono stati ottenuti con i derivati p-Me, m,p-diMe and p-Et fenil 3c, 3e e 3f, rispettivamente, i quali sono risultati essere equipotenti rispetto al composto di riferimento Combretastatina A-4 (CA-4).
Proseguendo nel nostro lavoro di ricerca, nel corso del secondo anno di dottorato, una nuova serie di composti caratterizzati dalla presenza di un gruppo 2-metossi/etossicarbonile sono stati valutati per l’attività antiproliferativa su linee cellulari tumorali e per i composti più attivi della serie si è andati a valutare l’inibizione della polimerizzazione della tubulina, gli effetti sul ciclo cellulare e l’attività antitumorale in vivo.
I migliori risultati in termini di attività antiproliferativa si sono ottenuti introducendo il sostituente metossilico in posizione C-6. Il composto più attivo della serie è risultato essere il derivato 2-metossicarbonil-3-(3’,4’,5’-trimetossianilino)-6-metossi-benzo[b]furano 3g, il quale ha prodotto una inibizione della proliferazione di linee cellulari tumorali a concentrazioni nanomolari (IC50’s, 0.3-27 nM), lega la tubulina a livello del sito di legame della colchicina, induce l’apoptosi e ha mostrato, sia in vitro che in vivo, una potente attività antivascolare su cellule endoteliali vascolari.
Infine durante il terzo anno di dottorato è stata messa a punto la sintesi di una nuova serie di inibitori della polimerizzazione della tubulina a struttura 1- (3’,4’,5- trimetossiifenil) -2-aril-1H-imidazolica e progettati come cis-analoghi della combretastatina A-4, con l’obiettivo di valutare l’effetto sull’attività biologica prodotto dall’introduzione di diversi gruppi sostituenti a livello dell’anello fenilico in posizione C-2 dell’eterociclo imidazolico. L’introduzione di un atomo di cloro e di un gruppo etossilico nelle posizioni meta- e para-, rispettivamente, ha prodotto il composto più attivo della serie 1-(3’,4’ ,5’ -trimetossifenil)-2-(3’-Cl, 4’-OEt fenil)-1H-imidazolo 4o, con un valori di IC50 di 0.4-3.8 nM su un pannello di sette linee cellulari tumorali. Esperimenti condotti su un modello di topo singenico hanno dimostrato una potente attività antitumorale del composto 4o, il quale ha prodotto una significativa riduzione della massa tumorale a dosi trenta volte più basse rispetto a quelle richieste per la CA-4P usato come composto di riferimento.<br>During these three years of PhD our research work has been focused on the design, synthesis and optimization of novel potential anticancer agents with antivascular and antiproliferative activities which target microtubules, dynamic tubular proteins that are assembled from α tubulin/β tubulin (αβ-tubulin) heterodimers.
The microtubule system is essential in a variety of fundamental cellular processes, including mitosis, formation and maintenance of cell shape, regulation of motility, cell signaling, secretion and intracellular transport.
Among natural occurring compounds, Combretastatin A-4 (CA-4), a cis-stilbene isolated from the bark of the South African bush willow tree Combretum caffrum , is one of the most potent inhibitors of colchicine binding presently known. CA-4 has been shown to possess a powerful cytotoxic activity against a panel of tumor cell line, including multi-drug resistant cells.
During the first year of PhD, a new class of compounds that incorporated the structural motif of the 1-(3’,4’,5’-trimethoxtbenzoyl)-3-arylamino-5-amino-1,2,4-triazole molecular skeleton was synthesized and evaluated for their in vitro antiproliferative activity, interactions with tubulin and cell cycle effects. The most active agent,( 1-(3,4,5-trimethoxybenzoyl)-3-(p-toluyl)-5-ammino-1,2,4-triazole, 3c), was evaluated for antitumor activity in vivo. The best results for inhibition of cancer cell growth were obtained with the p-Me, m,p-diMe and p-Et phenyl derivatives 3c, 3e and 3f, respectively, and, overall, these compounds were more or less as active as CA-4. Their vascular disrupting activity was evaluated in HUVEC cells, with compound 3c showing activity comparable with that of CA-4. Compound 3c almost eliminated the growth of syngeneic hepatocellular carcinoma in Balb/c mice, suggesting that 3c could be a new antimitotic agent with clinical potential.
During the second year a new series of compounds characterized by the presence of a 2-methoxy/ethoxycarbonyl group were evaluated for antiproliferative activity against cancer cells in culture, and, for selected, highly active compounds, inhibition of tubulin polymerization, cell cycle effects and in vivo potency. The greatest antiproliferative activity occurred with a methoxy group introduced at the C-6 position, the least with this substituent at C-4. Thus far, the most promising compound in this series was 2-methoxycarbonyl-3-(3’,4’,5’-trimethoxyanilino)-6-methoxybenzo[b]furan (3g), which inhibited cancer cell growth at nanomolar concentrations (IC50’s, 0.3-27 nM), induced apoptosis and showed, both in vitro and in vivo, potent vascular disrupting properties derived from the effect of this compound on vascular endothelial cells. Compound 3g had in vivo antitumor activity in a murine model comparable to the activity obtained with combretastatin A-4 phosphate.
The research work of the third year of PhD has been focused on the synthesis of a novel series of tubulin polymerization inhibitors, based on the 1-(3’,4’,5’-trimethoxyphenyl)-2-aryl-1H-imidazole scaffold, with the goal of evaluating the effects of various patterns of substitution on the phenyl at the 2-position of the imidazole ring on biological activity. A chloro and ethoxy group at the meta- and para-positions, respectively, produced the most active compound in the series (1-(3’,4’ ,5’ -trimethoxyfenyl)-2-(3’-Cl, 4’-Ethoxyfenyl)-1H-imidazole ,4o), with IC50 values of 0.4-3.8 nM against a panel of seven cancer cell lines. Except in HL-60 cells, 4o had greater antiproliferative than CA-4, indicating that the 3’-chloro-4’-ethoxyphenyl moiety was a good surrogate for the CA-4 B-ring. Experiments carried out in a mouse syngenic model demonstrated high antitumor activity of 4o, which significantly reduced the tumor mass at a dose thirty times lower than that required for CA-4P, which was used as a reference compound.
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Ekici, Özlem Doğan. "Design, synthesis, and evaluation of novel irreversible inhibitors for caspases." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04062004-164633/unrestricted/ekici%5Fozlem%5Fd%5F200312%5Fphd.pdf.
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Agarwal, Anil Kumar. "Design and synthesis of novel bacterial enzyme inhibitors as potential antituberculosis agents." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445382.
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Wilson, Kris. "Novel screening techniques for the discovery of human KMO inhibitors." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/18743.
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Kynurenine 3-monooxygenase (KMO) is an enzyme central to the kynurenine pathway of tryptophan degradation. KMO is emerging as an increasingly important target for drug development. The enzyme is implicated in the development and progression of several neurodegenerative disorders, in the regulation of the immune response and in sterile systemic inflammation. Production of recombinant human enzyme is challenging due to the presence of transmembrane domains, which localise KMO to the outer mitochondrial membrane and render KMO insoluble in many in vitro expression systems. Although several in vitro KMO assay techniques have been reported in the literature these methods are typically insensitive or require purified protein for use in high-throughput screening assays of human KMO enzyme. The first report of bacterial expression of soluble active human KMO enzyme is described here. Fusion protein tags were used to optimise soluble expression and enable characterisation and partial purification of the active protein constructs. Functional enzyme was used to develop several novel high-throughput drug screening techniques for the discovery of inhibitors specifically targeting human KMO. These screening techniques were fully characterised and validated using known KMO inhibitors from the patent literature. One of the novel KMO assay techniques was implemented for compound screening and several hit compounds were identified, validated and their in vitro DMPK characteristics determined. In addition to assay development, KMO was characterised at the cellular level when overexpressed in HEK293 cells. These experiments indicated that KMO overexpressing cells undergo bidirectional adaptation via alteration of kynurenine pathway homeostasis. As a result, these cells are protected from cytotoxicity mediated by 3-hydroxykynurenine (3-HK), the toxic product of KMO catalysis. The development of novel high throughput screening techniques targeting KMO has enabled screening of potential new inhibitors specifically targeting the human enzyme. Implementation of these screening assays will allow accelerated and improved discovery and development of novel KMO inhibitors for the potential treatment of numerous disease states.
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Suhuai, Liu. "Novel C-linked antifreeze glycoprotein (AFGP) analogues as potent recrystallization inhibitors: Preparation, assessment and in vitro studies." Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/29359.
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Antifreeze glycoproteins (AFGPs) are a subclass of biological antifreezes found primarily in the plasma of Teleost fish inhabiting in sub-zero temperature environments. These compounds have the ability to inhibit the growth and recrystallization of ice, thus ensuring the survival of these organisms in subzero environments. This characteristic property is highly desirable for medical and commercial applications. However, the limited bioavailability and the inherent instability of native AFGPs have precluded their commercialization. Consequently, rationally designed C-linked AFGP analogues are very attractive. This work describes the preparation of stable C-linked AFGP analogues and the evaluation of their antifreeze-specific activities. The in vitro behaviors of AFGP8 and C-linked AFGP analogues are also described.
A new series of C-linked AFGP analogues was prepared to evaluate the functions of the length and rigidity of the side chain between the carbohydrate moiety and the polypeptide backbone, the acetamide group in the galactosamine residue, and the polypeptide backbone. C-linked AFGP analogues containing three and four methylene groups in the side chain were prepared using an olefin cross-metathesis (OCM) method. C-linked AFGP analogues containing a C-glycosylated L-serine residue were prepared using a catalytic asymmetric hydrogenation (CAH) strategy. A neoglycopolymer with the polymeric chain composed of alternating ethylene groups and cyclopentane rings was prepared using the ring-opening metathesis polymerization (ROMP).
The new series of C-linked AFGP analogues was evaluated for their antifreeze-specific activities, including thermal hysteresis (TH) and recrystallization inhibition (RI). Although no TH activity was displayed in any analogues, some analogues demonstrated potent RI activity. These examples with tailored RI and TH activities suggest that it is possible to design AFGP analogues for different applications.
The behaviors of AFGP8 and two C-linked AFGP analogues with potent RI activity were studied in vitro. High concentration AFGP8 demonstrated significant toxic effects to human liver and kidney cells at both physiological and cryogenic temperatures. In contrast, C-linked AFGP analogues did not show any cytotoxicity in human cell lines under the same conditions. A caspase-3/7 assay and an independent fluorescence apoptosis assay verified that the cytotoxicity caused by AFGP8 was due to the induction of apoptosis, while C-linked AFGP analogues could inhibit the activation of caspase 3 and 7. In addition, an internalization study demonstrated that both AFGP8 and the C-linked AFGP analogues shared the same cellular uptake mode and intracellular pathway.
The cytotoxicity of AFGP8 may limit its applications in the biological systems. In contrast, our C-linked AFGP analogues are not cytotoxic and can inhibit the activation of caspase 3 and 7. In addition, since they have no TH activity, no detrimental ice spicules will be formed. Therefore, these C-linked AFGP analogues have an advantage for being used as cryoprotectants for cell preservation.
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Stimac, Robert. "Macrocyclic Carbon Suboxide Derivatives Novel Potent Inhibitors of the Na,K-ATPase, and their Mechanism of Inhibition /." [S.l. : s.n.], 2005. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11729978.
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Di, Maria Salvatore. "Development of novel pyrazolo[3,4-d]pyrimidines as anticancer agents: synthesis of potent c-Src/Abl inhibitors." Doctoral thesis, Università di Siena, 2021. http://hdl.handle.net/11365/1140488.
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The interest in protein tyrosine kinases has increased in recent years, particularly since their
oncogenicity in human cells has been recognized. Tyrosine kinases promote phosphorylation of many
proteins involved in cellular signaling pathways and the deregulation of their normal activity leads to
diseases, such as cancer. In this context, several pyrazolo[3,4-d]pyrimidines have been developed as
Tyrosine Kinase Inhibitor (TKI) and some of them have revealed promising in vitro and in vivo
antitumor activity. In this thesis I describe the work done during my three years of PhD, which
concerns the design and synthesis of novel pyrazolo[3,4-d]pyrimidines able to inhibit the protein
tyrosine kinase c-Src and Abl, involved in cancer processes. The first chapter provides a general
introduction on Protein Kinases, focusing on the major non-receptor tyrosine kinases c-Src and Abl.
Here, the protein activation mechanisms and some structural aspects have been described. The second
chapter is dedicated to the development of potent c-Src/Abl inhibitors for the treatment of Chronic
Myeloid Leukemia (CML). Optimization of molecules, through the design and synthesis of novel
derivatives, has been successfully performed and new promising anticancer agents have been
obtained. The third chapter describes the elaboration of five novel families of pyrazolo[3,4-
d]pyrimidines designed through merge-hybridization with TKIs approved in cancer therapy. Thereby,
a small library of c-Src inhibitors against Hepatocellular Carcinoma (HCC) has been developed.
Finally, the last chapter illustrates the optimization process of two pyrazolo[3,4-d]pyrimidine
compounds, Si306 and Si409, with the aim of improving some pharmacological properties for the
treatment of Glioblastoma Multiforme (GBM) through the design and synthesis of a small set of
derivatives.
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Sekgota, Khethobole Cassius. "Design, development and evaluation of novel lead compounds as HIV-1 enzyme inhibitors." Thesis, Rhodes University, 2015. http://hdl.handle.net/10962/d1017926.
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This project has been concerned with the application of the Baylis-Hillman methodology to the synthesis of medicinally important diketo acid analogues (cinnamate ester-AZT conjugates and 3-hydroxy ester-AZT conjugates) as dual-action HIV-1 IN/RT inhibitors; and on exploratory studies in the preparation of 3-(amidomethyl)-(1H)-2-quinolones as PR inhibitors; and (1H)-2- quinolone-AZT conjugates as dual action IN/RT inhibitors. A series of Baylis-Hillman adducts has been prepared, typically in moderate to excellent yield, by reacting 2-nitrobenzaldehyde with methyl acrylate, ethyl acrylate and methyl vinyl ketone in the presence of 1,4- diazabicyclo[2.2.2]octane (DABCO). Subsequently, various transformations that include conjugate addition of primary and secondary amines to the α,ß-unsaturated moiety to obtain 2- (aminomethyl)-3-hydroxy-3-(2-nitrophenyl)propanoate derivatives, effective SN2´ substitution of the BH ß-hydroxy by a Vilsmeier-Haack in situ-generated chloride to afford Baylis-Hillman allyl chlorides, iron in acetic acid-catalyzed cyclisation to 3-acetoxymethyl-(1H)-2-quinolone derivatives were achieved. Thus, using the Baylis-Hillman methodology, two nuanced classes of diketo acid analogues were constructed. These involved conjugating appropriate propargylamine derivatives with AZT using the „click‟ reaction. In an exploratory study, the quinolone derivative, precisely 3-acetoxymethyl- (1H)-quinol-2-one, was transformed into 3-hydroxymethyl-(1H)-quinol-2-one using potassium carbonate in a mixture of methanol and water (1:1). Following successful hydrolysis, the resulting alcohol was transformed to the corresponding chloride, 3-chloromethyl-(1H)-quinol-2- one, using thionyl chloride. Subsequent nucleophilic substitution afforded 3-(aminomethyl)- (1H)-2-quinolone derivatives which were subsequently transformed to 3-(amidomethyl)-(1H)-2- quinolones; and 3-[(propargylamino)-methyl]-(1H)-quinol-2-one as precursors to quinolone- AZT derivatives. All compounds were characterized by NMR, IR, and where appropriate, high resolution MS
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Koizumi, Fumito. "Studies on the novel inhibitors of interleukin-1β converting enzyme from microbial sources". Kyoto University, 2005. http://hdl.handle.net/2433/144583.
Full textAbstract:
Kyoto University (京都大学)<br>0048<br>新制・論文博士<br>博士(農学)<br>乙第11725号<br>論農博第2574号<br>新制||農||919(附属図書館)<br>学位論文||H17||N4087(農学部図書室)<br>23622<br>UT51-2005-K529<br>(主査)教授 大東 肇, 教授 吉川 正明, 教授 村田 幸作<br>学位規則第4条第2項該当
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Darkins, Paul Anthony. "Synthesis and enzyme inhibitory properties of novel proteinase inhibitors derived from enantiopure #alpha#-diazoketones." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318839.
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Holt-Martyn, James. "Novel and selective small molecule inhibitors and activators for the prolyl hydroxylase domain enzyme." Thesis, University of Oxford, 2018. http://ora.ox.ac.uk/objects/uuid:4b3613c5-5ff3-43b0-a07e-cf3116a37c1b.
Full textAbstract:
Hypoxia Inducible Factors (HIF) functions are master regulators of oxygen homeostasis and have a key role in the physiological responses to hypoxia including angiogenesis and erythropoiesis. Under hypoxia, levels of HIF-α subunits increase, they hetereodimerise with HIF-1β sub unit and promote the initiation of transcription of target genes. Under normoxia, oxygen dependent HIF-α degradation is promoted by hydroxylation of either of two proline residues (Pro402 and Pro564). The interaction of prolylhydroxylated HIF-α with the Von Hippel-Lindau protein (pVHL) promotes hydrolytic degradation of HIFα through an E3 ubiquitin ligase proteasomal pathway. HIF prolyl hydroxylation is catalysed by three 2-oxoglutarate (2OG)-dependent oxygenases known as prolyl hydroxylase domain (PHD 1-3) proteins, through an Fe(II) mediated catalytic process using 2OG, and oxygen. The PHDs are part of the family of Fe(II) bound 2OG dependent oxygenases. There are approximately 70 human 2OG oxygenases many of which have biologically important roles. Small-molecule inhibitors have reached advanced clinical trials; however, many clinical candidates inhibit other structurally similar 2OG oxygenases (OGFOD1 and vCPH) potentially altering the therapeutic effect. This thesis describes the design and synthesis of potent and 2OG oxygenase selective inhibitors for the PHDs. The 1,3,8-triazaspiro[4.5]decane-2,4-dione and 4-hydroxy-2-(pyrazole)pyrimidine-5-amide series were chosen as initial 'hits' (reported in the patent literature). The main analogues of the series were characterised in vitro and in cells as potent and selective PHD inhibitors over structurally similar 2OG oxygenases (Chapter 2). Broad structure activity relationship (SAR) of both initial series demonstrated the sensitivity for PHD2 inhibition (Chapter 3). Combination of SAR work described in Chapters 2 and 3 lead to the development of the novel 4-hydroxy pyridine series. In-depth SAR resulted in optimised analogues including 1 (IC50 69 nM) and highly selective over structurally similar 2OG oxygenases including OGFOD1. The completed SAR work led to the development of two novel pharmacophores 2 and 3. Both pharmacophores displayed potent PHD inhibition and selectivity over OGFOD1. Analogues including 1 and 3 displayed on target cellular activity stabilising HIF-1α at 20 μM (Chapter 4). The 4-dimethylamine pyridine analogue displayed an increase in substrate hydroxylation on PHD2 in contrast to the DMSO control (Chapter 3). SAR and cellular characterisation indicated that the effect observed was not an assay artifact (Chapter 5). Fenofibrate was used as a starting point for the development of novel inhibitors of the oxygen consumption rate (OCR) via mitochondrial inhibition (Chapter 6). Analogues were synthesised in order to conduct broad SAR and on-target cellular activity was observed in a Seahorse XF assay (50% reduction in the OCR at 1 μM). A selection of amino and amide analogues warrant further investigation.
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Lauria, S. "THE ENDOCANNABINOID ENZYME MONOACYLGLYCEROL LIPASE: DEVELOPMENT OF A NEW FLUORESCENT ASSAY AND NOVEL INHIBITORS." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/336675.
Full textAbstract:
The endocannabinoid system (ECS), comprising CB1/CB2 receptors, endocannabinoids (ECs) and their metabolic enzymes, FAAH (fatty acid amide hydrolase) and MAGL (monoacylglycerol lipase), is responsible for maintaining the homeostatic balance, regulating and modulating the physiological responses to improve general well-being [1]. A dysregulation of ECS is connected to pathological conditions such as pain, inflammation, anxiety, and other disorders [2]. Pharmacological blockade of FAAH and MAGL has emerged as a potentially attractive strategy to augment EC signalling and retain the beneficial effects of cannabinoid receptor activation, while avoiding the undesirable side effects, such as impairments in cognition and motor control, observed with direct cannabinoid receptor agonists [3].
The endogenous serine-hydrolase MAGL is the main enzyme responsible for inactivating endocannabinoid agonist 2-arachidonoylglycerol (2-AG) to arachidonic acid and glycerol. Conventional assays for MAGL activity and inhibitors screening utilize radiolabelled substrates [4] or MAGL-catalysed hydrolysis of p-nitrophenyl alkyl esters allowing the liberation of UV-detectable p-nitrophenol [5].
Furthermore, a fluorescence-based assay has been developed applying 7-hydroxycoumarinyl arachidonate (7-HCA) [6] or HPLC method with fluorescence detection using as fluorogenic probe 1,3-dihydroxypropan-2-yl-4-pyren-1-ylbutanoate [7].
The objective of this PhD project was to:
- develop a new sensitive MAGL-activity assay simple, sensitive, and suitable for high-throughput screening (HTS) to test potential inhibitors, both in vitro and in cell cultures;
- synthesise more potent and selective inhibitors in order to increase the endogenous level of EC prolonging their action.
A first part of this project has been focused on the development of a novel fluorescent method for assaying MAGL. Therefore, we designed and synthesized 7-hydroxyresorufinylarachidonate (7-HRA) which is amenable for high-throughput screening (HTS). MAGL catalyses the hydrolysis of 7-HRA to generate arachidonic acid and a highly red fluorescent resorufin. Our new substrate [8] combines high specific reactivity with the enzyme tested with excellent stability against non-specific degradation if stored in the dark and can be a useful tool in further developments of MAGL inhibitors. Moreover, resorufin’s high red absorption and emission wavelengths should be preferred in cell cultures assays to blue emitting molecules in reason of the lower background absorbance and auto fluorescence of tissues in this spectral region [9]. Three known MAGL inhibitors were used to validate the test assay.
A second part of the project was the synthesis of reference molecule URB602 [10] and a library of analogues that were tested against MAGL with our new fluorescent method. Some of them showed encouraging results in terms of inhibitory activity, proving to have an increase in the activity compared to reference URB602.
A molecular modelling work was made to understand the possible interactions between each compound and the enzyme and to explain the differences among the different structures.
Moreover, the fluorescent method was applied to cancer cell lysates to verify its suitability for in vitro experiments - which was confirmed - and a first screening on the new inhibitors was made on these cell lines, finding that their activity is comparable to that of URB602.
References
[1] P. Pacher et al., Pharmacol. Rev. 58 (2006) 389-462
[2] J.Z. Long et al., Nat. Chem. Biol. 5 (2009) 37–44
[3] J.Z. Long et al., P. Natl. Acad. Sci. USA 106 (2009) 20270-20275
[4] J. Brengdahl et al., Anal. Biochem. 359 (2006) 40-44
[5] G.G. Muccioli et al., ChemBioChem 9 (2008) 2704-2710
[6] Y. Wang et al., Assay Drug Dev. Techn. 6 (2008) 387-393
[7] A. Holtfrerich et al., Anal. Biochem. 399 (2010) 218-224
[8] S. Lauria et al., Anal. Bioanal. Chem. (2015), 407, 8163-8167 DOI 10.1007/s00216-015-8991-9.
[9] M. Fritzsche et al., Anal. Bioanal. Chem. 398 (2010) 181-191
[10] M. Szabo et al., Bioorg. Med. Chem. Lett. 21 (2011) 6782-6787
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Watermeyer, Jean Margaret. "Structural determinants of the domain-selectivity of novel inhibitors of human testis angiotensin-converting enzyme." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/3154.
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Mahasenan, Kiran V. "Discovery of novel small molecule enzyme inhibitors and receptor modulators through structure-based computational design." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1332367560.
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GALBIATI, ANDREA. "DESIGN AND SYNTHESIS OF NOVEL ENZYME INHIBITORS AS ANTIPROLIFERATIVE COMPOUNDS WITH ANTIPROTOZOAL AND ANTICANCER ACTIVITY." Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/827428.
Full textAbstract:
This dissertation describes the research carried out as part of a PhD program in Chemistry
from the 1st October 2017 until 30th November 2020. The PhD project investigated the
development of inhibitors of enzymes involved in important metabolic pathways, with the
final aim to produce an antiproliferative effect. The present thesis combines the works
performed at the University of Milan and Vrije Universiteit of Amsterdam.
Part A describes the research performed in Amsterdam, NL during my period abroad from
January to September 2019 in the research group of Professor Rob Leurs, at the Division of
Medicinal Chemistry of the Amsterdam Institute for Molecules, Medicines and Systems,
Vrije Universiteit of Amsterdam. In particular, this part outlines the design, synthesis and
pharmacological evaluation of two novel series of potent antitrypanosomal agents,
identified through SAR exploration and scaffold hopping approach starting from cyclic
nucleotide Trypanosoma brucei phosphodiesterase (PDE) inhibitors. PDE enzymes provide
a fine control on several biochemical pathways and have recently been demonstrated to
be essential for parasite proliferation. Their disruption by RNA interference (RNAi)
dramatically increase intracellular cAMP and, consequently, causes complete mortal
trypanosome cell lysis.
Part B describes the research done at the Department of Pharmaceutical Sciences,
University of Milan, under the supervision of Professor Paola Conti, on the design and
synthesis of novel covalent inhibitors targeting the glycolytic enzyme Glyceraldehyde-3-
phosphate dehydrogenase (GAPDH). Due to its pivotal role in the glycolysis, GAPDH
represents a rate-limiting enzyme in those cells that mostly, or exclusively rely on this
pathway for energy production. In this context, GAPDH inhibition represents a valuable
approach for the development of anticancer and antiparasitic drugs. Due to the presence
of a druggable nucleophilic cysteine residue in the catalytic pocket of the target, I focused
my attention on the development of covalent GAPDH inhibitors, presenting an electrophilic
warhead with a finely tuned reactivity. In particular, Section B2 reportsthe work conducted
on the development of Plasmodium falciparum GAPDH inhibitors and the in vitro
antiplasmodial activity. Section B3 shows the work performed on the design and synthesis
of human GAPDH inhibitors, with in vitro antitumor activity.
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Lee, Yi-Chen. "Studies towards the development of novel HIV-1 integrase inhibitors." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005022.
Full textAbstract:
The project has focused on the preparation of several series of compounds designed as potential HIV-1 integrase inhibitors. Various 2-nitrobenzaldehydes have been reacted with two activated alkenes, methyl vinyl ketone (MVK) and methyl acrylate, under Baylis-Hillman conditions to afford α-methylene-β-hydroxylalkyl derivatives in moderate to excellent yields. The reactions were conducted using the tertiary amine catalysts, 1,4-diazabicyclo[2.2.2]octane(DABCO) or 3-hydroxyquinuclidine (3-HQ) with chloroform as solvent, and yields were optimised by varying the catalyst, reagent concentrations and the reaction time. Reductive cyclization of the Baylis-Hillman adducts via catalytic hydrogenation, using 10% palladiumon-carbon catalyst in ethanol, afforded quinoline and quinoline N-oxide derivatives. In some cases “acyclic” reduction products were also isolated. Reaction of the Baylis-Hillman MVK adducts with HCl, has resulted in effective nucleophilic (SN’) displacement of the hydroxyl group to afford allylic chloride derivatives. Direct substitution of these chloro derivatives by secondary or primary amines, followed by catalytic hydrogenation gave quinoline derivatives containing a 3-aminomethyl substituent. The Baylis-Hillman ester adducts obtained from reaction with methyl acrylate were treated directly with various amines to give diastereomeric conjugate addition products. Reactions with piperazine gave N,N’-disubstituted piperazine products. The piperidine derivatives have been dehydrated to give cinnamate esters in moderate yields. The products, which have all been satisfactorily characterised by elemental (HRMS) and spectroscopic (1- and 2-D NMR) analysis, constitute a “library” of compounds for in silico and in vitro studies as potential HIV integrase inhibitors.
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Chee, Soo Mei. "Design, synthesis and biological evaluation of the novel inhibitors of enzymes NQO1 and NQO2." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/design-synthesis-and-biological-evaluation-of-the-novel-inhibitors-of-enzymes-nqo1-and-nqo2(14689fca-4a77-4102-8f55-49c90be6fa72).html.
Full textAbstract:
A range of novel and potent NQO1 and NQO2 inhibitors were synthesised. A series of 4-hydroxycoumarin analogues were prepared and assayed against NQO1. Furthermore, a more efficient synthetic route was developed by employing the “borrowing hydrogen” methodology. All the synthetic unsymmetrical dicoumarol analogues were novel and potent NQO1 inhibitors with IC50¬ values in the nanomolar range. The most potent analogues were non-toxic against the non-small cell lung cancer cell line, A549.The potential NQO2 inhibitors were classified in three different groups based on their core structure: 4-aminoquinolines, 7-chloro-4-aminoquinolines and 6-methoxy-4-aminoquinolines, where each group comprises of the following four subsets: the N-phenylated-, N-benzylated-, N-benzoylated- and the 4-hydrazinoquinoline analogues. Most of the quinoline analogues were found to be potent NQO2 inhibitors with IC50 values in the nanomolar range with the exception of the N-phenylated subset. The most potent analogues were toxic against the human breast adenocarcinoma cell line, MDA-MB-468.
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Bailey, Helen Victoria. "Drug design and novel anti-cancer therapeutics : inhibitors of 17β hydroxysteroid dehydrogenase type 3". Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512267.
Full textAbstract:
Herein, we describe the design and synthesis of novel inhibitors of 17β-hydroxysteroid dehydrogenase type 3 which convert androstenedione into testosterone, which is then converted into dihydrotestosterone (DHT). This isozyme has been implicated in the growth of prostate cancer. Using an in silico pharmacophore model initial targets were planned, based around a diphenylether hydrophobic head linked to a 4-substituted piperidine ring. Over 45 compounds were synthesised and many show significant biological activity when evaluated in a 17β-HSD type 3 biological assay. The most potent compound in this series is 1-(4-[2-(4-chloro-phenoxy[-phenylamino]-piperidin)1-yl) ethanone with an IC₅₀ of 700 nM. The amine linked compounds are significantly more active than the amide equivalents. Synthesis of the amine-linked compounds was problematic and led to the development of a novel and general microwave assisted procedure for the reductive amination of anilines, enabling aromatic amine-linked compounds to be synthesised in excellent yields. A series of benzylamine linked inhibitors was also prepared. Over 30 analogues were synthesised and several show very promising biological activity. The most active compound is N-(2-([2-(4-Chloro-phenoxy)-phenylamino]-methyl)-phenyl)-acetamide, which exhibits an IC₅₀ of 900 nM. The synthesis of compounds with a benzophenone linked hydrophobic head group led to an unexpected product. X-ray crystallography was used to determine the structure, as a quinoline derivative. This led to optimisation of a novel modification of the Friedländer synthesis of quinolines. The potent inhibitors synthesised are selective over 17β-HASD Types 1 and 2. One inhibitor also shows potentially interesting activity against the leukaemia cell line CCRF-CEM, in the NCI screening, with a GI₅₀ of 10 nM.
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Bourgeois, Karine. "Towards in vitro Pharmacokinetic Assessment of Novel Targeted Covalent Inhibitors for Human Tissue Transglutaminase." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39472.
Full textAbstract:
Human tissue transglutaminase (TG2) is a calcium-dependent multifunctional enzyme that natively catalyzes the post-translational modification of proteins, namely by the formation of isopeptide bonds between protein- or peptide-bound glutamine and lysine residues. This ubiquitously expressed enzyme plays important roles in cellular differentiation, extracellular matrix stabilization, and apoptosis, to name a few. However, its unregulated activity has been associated with many pathologies such as fibrosis, cancer, neurodegenerative disorders and celiac disease. Most of these disorders are associated with unregulated acyl-transferase activity. As such, the Keillor group has directed its efforts towards the development of TG2 inhibitors.
Over the years, the Keillor group has synthesized large libraries of targeted covalent inhibitors against TG2. These compounds have undergone pharmacodynamic testing in order to examine their kinetic parameters of inhibition. Having gained knowledge of their enzyme kinetics, the logical next step was to consider their pharmacokinetic profiles. In the context of this thesis, we considered two important pharmacokinetic properties: membrane permeability and off-target reactivity.
Firstly, we aimed to evaluate our inhibitors for their ability to permeate the cell membrane. In efforts to do so, we were able to adapt, optimize, and validate a parallel artificial membrane permeability assay (PAMPA) utilizing hexadecane as our artificial membrane. We were able to test a few of our own inhibitors and found that compounds NC9, VA4 and AA9 possess Log Pe values of -5.26 ± 0.01, -4.66 ± 0.04 and -6.5 ± 0.5 respectively.
Secondly, we sought to investigate the susceptibility of our inhibitors to glutathione addition reactions under physiological conditions. We adapted and optimized a colorimetric assay using Ellman’s reagent (DTNB) and found that our inhibitors are minimally reactive with glutathione.
The methods developed over the course of this work provide protocols that can be adopted for the characterization of future inhibitors in the Keillor group, along the process of developing TG2 inhibitors into drug candidates.
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Sachdeva, Sarbjot Singh. "Interactions of mtFabH with its Substrates and Inhibitors Reveal Novel Mechanistic Insights." VCU Scholars Compass, 2007. http://scholarscompass.vcu.edu/etd/1483.
Full textAbstract:
Tuberculosis emerged from its grave to be one of the deadliest diseases of the present time after recently developing a synergy with AIDS. A fatty acid condensing enzyme-mtFabH has been proposed to connect the key processes involved in biosynthesis of mycolic acids, an important component of mycobacterial cell wall. It condenses long acyl Coenzymes A (CoA; up to C20CoA) with malonyl Acyl Carrier Protein (ACP) to form the elongated β-ketoacyl-ACP which further undergoes rounds of elongation to form mero-mycolate branch of mature mycolic acids. Owing to its proposed central position in mycolic acid synthesis, mtFabH has attracted considerable attention as a good anti-mycobacterial target.In this study, we utilized important biochemical tools such as site directed mutagenesis, mass spectrometry and X-ray crystallography to address some of the key unanswered questions regarding the intricate workings of mtFabH. We solved the first co-crystal structure of substrate C12CoA with mtFabH and further analyzed the substrate specificity of this acylation step. This structure depicts the mode of acyl-CoA binding in mtFabH channels; and its comparison with the parallel E.Coli-acetyl CoA structure provides important similarities and differences in substrate binding in these two FabH enzymes. It also posed an important question about the trajectory of long acyl chain CoA into the deep and "seemingly closed" substrate binding pocket of mtFabH. By utilizing disulfide-based inhibitors, we showed that large conformational changes are necessary to facilitate ligand trafficking in mtFabH while the high catalytic turnover rate of the enzyme is maintained. We also proposed the most likely location of the involved loop.A much faster and less cumbersome assay for mtFabH was also developed and it was utilized to characterize a series of inhibitors. This assay utilizes the commercially available radioactive malonyl-CoA in lieu of malonyl-ACP, the physiological substrate, and thus can serve as ACP independent assay for mtFabH.These studies further our understanding of the biochemistry of mtFabH, which along with the faster assay could be helpful in designing potent mtFabH inhibitors as anti-tubercular agents in the future.
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Dotse, Anthony Kwabla. "Design, synthesis and evaluation of novel inhibitors of cysteine proteases, metalloproteases and the proteasome, a unique high molecular weight proteolytic enzyme." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/29979.
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Lagerlund, Olof. "Design and Synthesis of Novel Glutamine Synthetase Inhibitors and Development of Palladium(0)-Catalyzed Aminocarbonylation." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, Uppsala universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-100377.
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Conibear, Anne Claire. "Synthesis and evaluation of novel inhibitors of 1-Deoxy-D-xylolose-5-phosphate reductoisomerase as potential antimalarials." Thesis, Rhodes University, 2013. http://hdl.handle.net/10962/d1008282.
Full textAbstract:
Malaria continues to be an enormous health-threat in the developing world and the emergence of drug resistance has further compounded the problem. The parasite-specific enzyme, 1-deoxY-D-xylulose-S-phosphate reductoisomerase (DXR), has recently been validated as a promising antimalarial drug target. The present study comprises a combination of synthetic, physical organic, computer modelling and bioassay techniques directed towards the development of novel DXR inhibitors. A range of 2-heteroarylamino-2-oxoethyl- and 2- heteroarylamino-2-oxopropyl phosphonate esters and their corresponding phosphonic acid salts have been synthesised as analogues of the highly active DXR inhibitor, fosmidomycin. Treatment of the heteroarylamino precursors with chloroacetyl chloride or chloropropionyl chloride afforded chloroamide intermediates, Arbuzov reactions of which led to the corresponding diethyl phosphonate esters. Hydrolysis of the esters has been effected using bromotrimethylsilane. Twenty-four new compounds have been prepared and fully characterised using elemental (HRMS or combustion) and spectroscopic (1- and 2-D NMR and IR) analysis. A 31p NMR kinetic study has been carried out on the two-step silylation reaction involved in the hydrolysis of the phosphonate esters and has provided activation parameters for the reaction. The kinetic analysis was refined using a computational method to give an improved fit with the experimental data. Saturation transfer difference (STD) NMR analysis, computer-simulated docking and enzyme inhibition assays have been used to evaluate the enzyme-binding and -inhibition potential of the synthesised ligands. Minimal to moderate inhibitory activity has been observed and several structure-activity relationships have been identified. In silica exploration of the DXR active site has revealed an additional binding pocket and information on the topology of the active site has led to the de novo design of a new series of potential ligands.<br>KMBT_363<br>Adobe Acrobat 9.54 Paper Capture Plug-in
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Guest, Patrick. "The identification and characterisation of novel inhibitors of the 17β-HSD10 enzyme for the treatment of Alzheimer's disease". Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/10398.
Full textAbstract:
In 2015, an estimated 46.8 million people were living with dementia, a number predicted to increase to 74.7 million by 2030 and 131.5 million by 2050. Whilst there are numerous causes for the development of dementia, Alzheimer's disease is by far the most common, accounting for approximately 50-70% of all cases. Current therapeutic agents against Alzheimer's disease are palliative in nature, managing symptoms without addressing the underlying cause and thus disease progression and patient death remain a certainty. Whilst the main underlying cause for the development of Alzheimer's disease was originally thought to be an abnormal deposition of insoluble amyloid-β peptide derived plaques within the brain, the failure of several high-profile therapeutic agents, which were shown to reduce the plaque burden without improving cognition, has recently prompted a shift in focus to soluble oligomeric forms of amyloid-β peptide. Such soluble oligomers have been shown to be toxic in their own right and to precede plaque deposition. Soluble amyloid-β oligomers have been identified in various subcellular compartments, including the mitochondria, where they form a complex with the 17β-HSD10 enzyme resulting in cytotoxicity. Interestingly, hallmarks of this toxicity have been shown to be dependent on the catalytic activity of the 17β-HSD10 enzyme, suggesting two therapeutic approaches may hold merit in treating Alzheimer's disease: disrupting the interaction between the 17β-HSD10 enzyme and amyloid-β peptide, or directly inhibiting the catalytic activity of the 17β-HSD10 enzyme. In 2006, Frentizole was identified as a small molecule capable of disrupting the 17β-HSD10/amyloid interaction. The work described herein details the generation of a robust screening assay allowing the catalytic activity of the 17β-HSD10 enzyme to be measured in vitro. This assay was subsequently employed for small molecule screening using two methodologies; first in a targeted approach using compounds derived from the Frentizole core scaffold, and second in an explorative manner using a diverse library of compounds supplied by the National Cancer Institute. As a result, a range of novel small molecule inhibitors of the 17β-HSD10 enzyme have been identified and the most promising characterised in terms of potency and mechanism of action. De-selection assays were developed to allow the efficient triage of hit compounds and work was begun on a cellular based assay which would allow the ability of compounds of interest to reverse a disease relevant phenotype to be assessed in a cellular environment. As such, we now have a number of hit compounds which will form the basis for the generation of subsequent series of derivatives with improved potency and specificity, as well as the robust assays required to measure such criteria, potentially leading to the generation of novel therapeutic agents against Alzheimer's disease.
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Lee, Alison Frances Clare. "The renin angiotensin aldosterone axis : relationships with other hormone systems, and novel applications for angiotensin converting enzyme inhibitors." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/22401.
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The aim of this thesis was to look at the renin angiotensin system both in clinical heart failure, and in relation to other physiological systems where an interaction may exist. Furthermore, to address new areas where a potential for benefit with Angiotensin Converting Enzyme (ACE) inhibitors might occur. To this end there are five studies discussed within the thesis. It is shown that in a group of heart failure patients, stabilised on maximum tolerated dose of ACE inhibitor, mean levels of plasma neurohormones were remarkably stable over 18 months. Reactivation of aldosterone occurred in 13/97 samples (13.5%) in 5/22 (23%) individuals, and reactivation of angiotensin II occurred in 8/102 samples (8%), in 6/22 (27%) individuals. These appear to be sporadic phenomenon, and contrary to previous dogma, they do not herald disease progression. Using endothelial function as a surrogate marker for cardiovascular events in hyperlipidaemic patients, it is shown that interruption of the renin angiotensin system using ACE inhibition, causes increases in both endothelial dependent and endothelial independent vasodilation. This could lead to the use of ACE inhibitors in hyperlipidaemic patients to reduce cardiovascular events, over and above traditional therapy such as statins. Subsequent to the above, the effect of lisinopril on nitrate/nitrite excretion as a marker of nitric oxide metabolism in hypercholesterolaemia was assessed. The levels of plasma nitrate/nitrite after an eighteen hour fast in twenty of the hyperlipidaemic volunteers were taken, and contrasted with values in normal volunteers. Lisinopril was found to have no effect on nitrate/nitrite levels in the hyperlipidaemic patients. Evidence in the literature has suggested interactions between the renin angiotensin system, and oestradiol, whose mechanism of vasodilation is still under debate. This study, using forearm plethysmography, looked at whether vasodilation by ovarian hormones was due to effects on the renin angiotensin system. No evidence was found that either oestradiol, or medroxy-progesterone affected vascular responses to angiotensin II, or altered the activity of vascular ACE activity.
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Kumar, Amit. "Synthesis and biochemical evaluation of novel enzyme inhibitors as potential anti-tumour agents in the treatment of breast cancer." Thesis, University of the West of Scotland, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.739948.
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Kaur, Gurpreet. "Synthesis of Boronic Acid Based Sensors for Glucose and Sialic Acid and Synthesis of Novel and Selective PDE4 Enzyme Inhibitors." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/chemistry_diss/9.
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The boronic acid functional group is known to bind compounds with the diol group tightly and reversibly in aqueous environment and has been used as a recognition moiety for the design of carbohydrate sensors. The first chapter of the dissertation studies the synthesis and substitution effect on the affinity and selectivity of a known boronic acid-based glucose sensor. In such a sensor design effort, the availability of a signaling event, whether it is fluorescence or UV, is crucial. The second chapter studies the detailed mechanism on how a well-known fluorescent boronic acid compound changes fluorescent properties upon binding. A new mechanism has been established which corrected a decade old mistake. In the third chapter, a series of boronic acid-based sensors were designed and synthesized for sialic acid, which is part of tetrasaccharide found on many cell surface carbohydrates. Such sialic acid sensors could be very useful for the development of new type of anti-influenza therapy. The fourth is on the design and synthesis novel and selective inhibitors for phosphodiesterase 4 (PDE4), which are potential anti-asthma agents.
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Mohamed, Ebrahim. "Probing the HIV reverse-transcriptase enzyme with novel bifunctional HIV-1 RT inhibitors of the general formula (NRTI)-spacer-(NNRTI)." Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/12152.
Full textAbstract:
Includes abstract.<br>Includes bibliographical references (leaves 224-233).<br>The high levels of resistance elicited by both nucleoside (NRTI) and non-nucleoside (NNRTI) reverse transcriptase inhibitors have prompted the design of double-drugs combining these two entities with the aim of addressing the emergence of resistance as well as searching for synergism between the two drug target sites on HIV reverse transcriptase (RT). The strategy involves combining two different inhibitors into a single chemical entity via a linker, with the aim of developing a mixed-site inhibitor combining the inhibitory actions of each drug. This thesis describes the rational drug-design and synthesis of nine bifunctional drugs combining a nucleos(t)ide and a non-nucleoside reverse transcriptase inhibitor linked via different non-cleavable spacers. The C-5 position of the nucleos(t)ide portion of the bifunctional was used for attachment of the spacer throughout. However, the site of attachment on the nonnucleoside drug varies according to the inhibitor type.
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Nichols, Derek Allen. "Structure-Based Design of Novel Inhibitors and Ultra High Resolution Analysis of CTX-M Beta-Lactamase." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5284.
Full textAbstract:
The emergence of CTX-M class-A extended-spectrum β-lactamases, which confer resistance to second and third-generation cephalosporins, poses a serious health threat to the public. CTX-M β-lactamases use a catalytic serine to hydrolyze the β-lactam ring. Specifically, the hydrolysis reaction catalyzed by CTX-M β-lactamase proceeds through a pre-covalent complex, a high-energy tetrahedral acylation intermediate, a low-energy acyl-enzyme complex, a high-energy tetrahedral deacylation intermediate after attack via a catalytic water, and lastly, the hydrolyzed β-lactam ring product which is released from the enzyme complex. The crystallographic structure of CTX-M at sub-angstrom resolution has enabled us to study enzyme catalysis as well as perform computational molecular docking in our efforts to develop new inhibitors against CTX-M. The goal of this project was to determine the hydrogen bonding network and proton transfer process at different stages of the reaction pathway as well as develop novel inhibitors against CTX-M β-lactamases. The results I have obtained from the project have elucidated the catalytic mechanism of CTX-M β-lactamase in unprecedented detail and facilitated the development of novel inhibitors for antibiotic drug discovery.
The first aim of the project focused on developing high affinity inhibitors against class A β-lactamase using a structure-based drug discovery approach, which ultimately led to the identification of CTX-M9 inhibitors with nanomolar affinity. Compound design was based on the initial use of computational molecular docking results along with x-ray crystal structures with known inhibitors bound in the active site. In addition, chemical synthesis was used to build and extend the existing inhibitor scaffold to improve affinity to CTX-M9 and related serine β-lactamases. Through a fragment-based screening approach, we recently identified a novel non-covalent tetrazole-containing inhibitor of CTX-M. Structure-based design was used to improve the potency of the original tetrazole lead compound more than 200-fold with the use of small, targeted structural modifications. A series of compounds were used to probe specific binding hotspots present in CTX-M. The designed compounds represent the first nM-affinity non-covalent inhibitors of a class A β-lactamase. The complex structures of these potent compounds have been solved using high resolution x-ray crystallography at ~ 1.2-1.4 Å, which provides valuable insight about ligand binding and future inhibitor design against class A β-lactamases.
Specifically, the first aim of the project was to use ultra-high resolution x-ray crystallography to study β-lactamase catalysis. Through the use of ultra-high resolution x-ray crystallography with non-covalent and covalent inhibitors, I was able to structurally characterize the critical stages of the enzyme mechanism. Here we report a series of ultra-high resolution x-ray crystallographic structures that reveal the proton transfer process for the early stages of the class A β-lactamase catalytic mechanism. The structures obtained include an a 0.89 Å crystal structure of CTX-M β-lactamase in complex with a recently-developed 89 nM non-covalent inhibitor, and a 0.80 Å structure in complex with an acylation transition state boronic acid inhibitor. Nearly all the hydrogen atoms in the active site, including those on the ligand, polar protein side chains and catalytic water, can be identified in the unbiased difference electron density map. Most surprisingly, compared with a previously determined 0.88 Å apo structure determined under the same conditions, the hydrogen-bonding network has undergone a series of reshuffling upon the binding of the non-covalent ligand. Two key catalytic residues, Lys73 and Glu166, appear to have both changed from a charged state to being neutral. Interestingly, structural evidence suggests the presence of a low barrier hydrogen bond (LBHB) shared between Lys73 and Ser70. These unprecedented detailed snapshots offer direct evidence that ligand binding can alter the pKa's of polar protein side chains and their affinities for protons. Such effects can be a common mechanism utilized by enzymes to facilitate the proton transfer process of a reaction pathway. They also have important implications for computational modeling of protein-ligand interactions. Ultra-high resolution x-ray crystallography allowed us to determine the hydrogen atom positions for key active site residues involved in catalysis. As a result, the ability to characterize the hydrogen bonding network led to the determination of the specific proton transfer process that occurs during the reaction stages of the CTX-M β-lactamase mechanism. Overall, the results from this project demonstrate the effectiveness of using ultra high resolution x-ray crystallography as a useful tool to study enzyme catalysis as well as develop and discover novel inhibitors.
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Hirsilä, M. (Maija). "Characterization of the novel human prolyl 4-hydroxylases and asparaginyl hydroxylase that modify the hypoxia-inducible factor." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514275756.
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Abstract
HIF prolyl 4-hydroxylases (HIF-P4Hs) and HIF asparaginyl hydroxylase (FIH) are novel members of the 2-oxoglutarate dioxygenase family that play key roles in the regulation of the hypoxia-inducible transcription factor (HIF). They hydroxylate specific proline and asparagine residues in HIF-α, leading to its proteasomal degradation and inhibition of its transcriptional activity, respectively. These enzymes are inhibited in hypoxia, and as a consequence HIF-α becomes stabilized, forms a dimer with HIF-β, attains its maximal transcriptional activity and induces expression of many genes that are important for cell survival under hypoxic conditions.
The three HIF-P4Hs and FIH were expressed here as recombinant proteins in insect cells and purified to near homogeneity. All these enzymes were found to require long peptide substrates. The three HIF-P4Hs and FIH acted differently on the various potential hydroxylation sites in the HIF-α isoforms. The HIF-P4Hs acted well on sequences with cores distinctly different from the core motif -Leu-X-X-Leu-Ala-Pro-, suggested based on sequence analysis studies, the alanine being the only relatively strict requirement in addition to the proline itself. Acidic residues around the hydroxylation site also played a distinct role. These results together with those of others provide evidence that there is no conserved core motif for the hydroxylation by HIF-P4Hs.
The Km values of the HIF-P4Hs for O2 were slightly above its atmospheric concentration, while the Km of FIH was about one-third of these values but still 2.5 times that of the type I collagen P4H. The HIF-P4Hs are thus effective oxygen sensors, as even small decreases in the amount of O2 affect their activities, while a more severe decrease is required to inhibit FIH activity. Small molecule inhibitors of the collagen P4Hs also inhibited the HIF-P4Hs and FIH but with distinctly different Ki values, indicating that it should be possible to develop specific inhibitors for the HIF-P4Hs and FIH.
The HIF-P4Hs were found to bind the iron cosubstrate more tightly than FIH and the collagen P4Hs, and the chelator desferrioxamine was an ineffective inhibitor of the HIF-P4Hs in vitro. Several metals were effective competitive inhibitors of FIH but they were ineffective inhibitors of the HIF-P4Hs. The well-known stabilization of HIF-1α by cobalt and nickel is thus not due to a simple competitive inhibition of the HIF-P4Hs, and is probably at least in part due to HIF-P4H-independent mechanisms. The effective inhibition of FIH by these metals nevertheless indicates that the stabilized HIF-1α is transcriptionally fully active.
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Pirrie, Lisa. "Development of novel active site and allosteric inhibitors of enzymes associated with cancer, neurodegenerative diseases and bacterial infections." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3471.
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The sirtuins are a family of NAD⁺-dependent deacetylase enzymes which are implicated in various illnesses including cancer and neurodegenerative diseases. Part I of this thesis describes the synthesis and biological evaluation of inhibitors of the SIRT1 and SIRT2 isoforms of this important family of enzymes. Chapter 1 gives an overview of sirtuin biology and the physiological roles of these enzymes. In particular the link between SIRT1 and cancer and SIRT2 and its role in the onset of neurodegenerative diseases is discussed. A review of the most potent and selective inhibitors of SIRT1 and SIRT2 is given including an introduction to the tenovin and cambinol classes of inhibitor. Chapter 2 describes various issues relating to the structure of the important chemical tool tenovin-6. The synthesis of analogues to improve the solubility, determine the preferred conformation and verify the products of metabolism of tenovin-6 is presented including their evaluation by in vitro and in cell methods. Part II of this chapter reports the design and use of a ¹H NMR method used to monitor the sirtuin-mediated deacetylation reaction. This was particularly relevant due to concerns raised about the possibility of false positive results obtained with the commercially available assay kit commonly used by the sirtuin community. This new ¹H NMR method was used to validate the inhibition of SIRT2 by tenovin-6. Chapter 3 describes the parallel synthesis and evaluation of tenovin analogues as inhibitors of SIRT1 and SIRT2. This study identified that replacement of the t-butyl substituent of tenovin-6 with the 3,5-dihalogen-4-alkoxy substitution pattern led to a variety of analogues having SIRT2 selectivity. As well as the collection of valuable SAR data, in cell data is also presented for the analogues. Chapter 4 provides attempts to rationalise the SAR data collected in Chapters 2 and 3 through a computational study. The molecular docking software GOLD was used to predict the binding site of the tenovin scaffold and hence rationalise the observed potencies of various analogues. Chapter 5 reports the synthesis and biological evaluation of triazole and cambinol analogues as SIRT1 and SIRT2 inhibitors. Part I details the synthesis and in vitro testing of a series of ring constrained tenovin analogues based on the 1,4-disubstituted triazole using click chemistry. A series of 1,5-disubstituted analogues were also synthesised. Part II describes the synthesis of S-alkylated cambinol analogues and the effect of N3-methylation upon activity and selectivity towards SIRT1. Part II of this thesis details the synthesis and biological testing of novel potent allosteric inhibitors of RmlA. RmlA is the first enzyme in the L-rhamnose biosynthetic pathway in bacteria. L-rhamnose is an important component of the bacterial cell wall and as such RmlA is therefore an important target in the discovery of novel anti-bacterial compounds. Chapter 7 provides an overview of the RmlA enzyme including its role in L-rhamnose biosynthesis and why it is an attractive target for anti-bacterial drug discovery. No small molecule inhibitors of RmlA have been reported previously. Chapter 8 describes the design and synthesis of pyrimidine-2,4-dione analogues as novel allosteric inhibitors of RmlA. SAR data is generated and rationalised by X-ray crystallographic techniques to study the structures of complexes of RmlA with various analogues. Analogues were also tested for their ability to inhibit the growth of the important human pathogen Mycobacterium tuberculosis.
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Srinivasan, Sheila. "The design and synthesis of novel heterocyclic inhibitors of the DNA-repair enzyme, poly(ADP-ribose) polymerase, as potential resistance-modifying agents." Thesis, University of Newcastle Upon Tyne, 1997. http://hdl.handle.net/10443/1022.
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The abundant nuclear enzyme, poly(ADP-ribose) polymerase (PARP) is activated by DNA strand breaks and catalyses the transfer of ADP-ribose moieties from its substrate, nicotinamide adenine dinucleotide (NAD), to various histone- or non-histone nuclear acceptor proteins. The net result is the formation of long, homopolymeric chains, the exact purpose of which is not clearly understood. Since this process is thought to facilitate DNA repair, the PARP enzyme represents a possible therapeutic target. A well known mechanism by which tumours become resistant to anticancer treatments is increased DNA repair. Inhibition of PARP may thus be a strategy for the potentiation of DNA-damaging agents and PARP inhibitors may function as resistance-modifying agents in conjunction with cancer chemotherapeutic agents. The aim of this research was to design and synthesise novel heterocyclic inhibitors of PARP, based on the existing knowledge of structure-activity requirements. A great deal of information has already been gathered from the use of early inhibitors, such as nicotinamide and 3-aminobenzamide (3AB). However, these inhibitors lack potency, specificity for the enzyme, and aqueous solubility, and so are limited in their use as clinical agents. A novel series of quinazolin-4-[3H]-ones (structure A) has been synthesised by a highyielding, reproducible pathway, including derivatives bearing electron-withdrawing and electron-donating substituents in the 2-position. These derivatives exhibit excellent in vitro PARP inhibitory activity, with IC50 values in the micromolar concentration range, and the selected compound, NU1025 (8-hydroxy-2-methylquinazolin-4-[3H]-one) has been shown to potentiate the effects of a range of mechanistically diverse anticancer agents, including y-irradiation. A water-soluble phosphate prodrug derivative of NU1025 has been synthesised and this shows promising enzyme-mediated conversion to the parent compound in plasma. A second series of 1H-benzimidazole-4-carboxamides (structure B) has been synthesised bearing mono-, di- or trisubstituted aryl rings in the 2-position. Biological evaluation of this series has shown that these derivatives are among the most potent PARP inhibitors reported to date, with K; values in the low nanomolar concentration range.
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Wilkinson, Brendan Luke. "Synthesis of Novel Carbohydrate Based Enzyme Inhibitor Libraries Utilising Click Chemistry." Thesis, Griffith University, 2007. http://hdl.handle.net/10072/366473.
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Within a short timeframe, the CuI-catalysed 1,3-dipolar cycloaddition (1,3-DCR) of an organic azide to a terminal acetylene to form a 1,4-disubstituted-1,2,3-triazole, has emerged as a powerful synthetic transformation in combinatorial chemistry, organic synthesis and bioconjugation research. This synthetic methodology, now known as click chemistry, has had an appreciable impact in the drug discovery and biotechnology sectors and has shown broad scope and compatibility with small molecule and polymeric substrates. The application of this powerful synthetic transformation, specifically in carbohydrate based drug discovery and glycobiology is a recent and emerging trend. Chapter one of this thesis is a review of the current literature concerning the use of click chemistry in carbohydrate based drug discovery and glycobiology. Several examples have appeared within the literature highlighting the potential of click chemistry for rapidly generating structurally diverse neoglycoconjugates, ranging from small molecule drug leads to multivalent constructs, as well as a bioconjugation strategy for labelling cell-surface glycoconjugates. The review aims to be exhaustive in its coverage, with emphasis on future perspective. This thesis presents the investigation of click chemistry as a synthetic tool in carbohydrate chemistry, and its application for generating novel carbohydrate based enzyme inhibitor libraries for lead discovery and optimisation purposes. Chapter two describes the utility of click chemistry and the glycosyl triazole moiety in synthetic carbohydrate chemistry. The reaction is well suited to the synthesis of mimetics of complex oligosaccharides and glycoconjugates, owing to the mild ambient nature and remarkable regio- and stereo- selectivity. The transformation was therefore interrogated under conditions typically encountered in carbohydrate chemistry, including glycosylation reactions and protective group manipulations. The study represents the first exhaustive investigation into the stability of the triazole moiety under these conditions as well as the synthetic utility of the CuI-catalysed 1,3-DCR as a potential orthogonal transformation in carbohydrate chemistry and an adjunct to existing methods. The first aspect of the study aimed to examine the stability of the glycosyl triazole moiety under conditions employed in protective group chemistry and the compatibility of the transformation with pre-installed functional groups. Using click chemistry, the triazole moiety could be introduced onto the carbohydrate scaffold in the presence of a wide range of protective functional groups. In addition, the 1,2,3-triazole moiety was indeed shown to be a robust entity that is compatible with essential protecting group manipulations and glycosylation chemistry - an important outcome with respect to its potential utility as an additional tool for the synthesis of oligosaccharide/glycoconjugate mimetics, which are often heavily reliant on orthogonal reaction sequences. Next, the utility of the reaction with respect to solvent and catalyst conditions was examined. The reaction was performed in different organic and aqueous solvents in the presence of two different CuI-catalyst systems. It was shown that the reaction is reasonably insensitive to the nature of the solvent or aqueous co-solvent and the catalyst system. Reaction times and yields displayed little variation with respect to the solvent and catalyst system. In all cases, the 1,4-disubstituted 1,2,3-glycosyl triazole model compound was isolated in high yields and required minimal purification. The work also amply demonstrated, in a proof-of-concept manner, the powerful scope of the reaction for preparing structurally diverse neoglycoconjugates in high yield and purity. Several artificial glycomimetics were prepared using a suite of glycosyl azides through the facile 1,3-DCR to a series of acetylenes. Chapter three presents an extensive study into the preparation and biological activity of glycoconjugate benzene sulfonamides as a novel class of carbonic anhydrase (CA) inhibitor. The conjugation of carbohydrate “tails” to a benzene sulfonamide pharmacophore provides access to CA inhibitors which are neutral, water-soluble and features high chiral density and polyfunctionality that may be exploited for tissue delivery applications and to survey active site architectures in order to impart isozyme selectivity. Glycoconjugate benzene sulfonamides could also display compromised plasma membrane permeability allowing for the selective targeting of tumour associated isozymes with extracellular catalytic domains. Glycoconjugate benzene sulfonamides have received little attention as CA inhibitors, and this work represents the first comprehensive study in the area. By utilising a novel “click-tailing” strategy developed in our laboratory, a panel of structurally diverse carbohydrate “tails” were appended to the primary arylsulfonamide (ArSO2NH2) pharmacophore. A panel of azido sugars and propargyl glycosides were reacted with acetylene- and azide-functionalised benzene sulfonamide scaffolds, respectively, and subsequently evaluated for their inhibition of human carbonic anhydrase (hCA) isozymes hCA I, II, IX, XII and XIV in vitro. In this manner, a total of 50 glycoconjugate benzene sulfonamides belonging to three libraries were prepared and assessed for their inhibition of human cystolic isozymes hCA I, II and transmembrane isozymes hCA IX, XII and XIV. Selective inhibition among CA isozymes is challenging owing to conservation of active site topology within this enzyme family, yet the design of selective CA inhibitors is necessary for the development of efficacious and safe CA-based therapeutics which are void of side effects arising from systemic CA inhibition. Many of the glycoconjugate benzene sulfonamides exhibited a non-clustered in vitro inhibition profile, demonstrating that the carbohydrate tail was a powerful structural element able to distinguish isozyme selectivity. A significant outcome of this study was the discovery of several potent and selective CA inhibitors of the tumour-associated transmembrane isozyme, hCA IX, and the physiologically dominant cytosolic isozyme, hCA II. Chapter four of this thesis explores the synthetic utility of click chemistry for the solution-phase synthesis of N-alkylated azasugar libraries. To date, click chemistry has seen limited application for the synthesis and screening of natural product-based libraries. To the best of my understanding, this work represents the first example of the use of click chemistry for the generation of azasugars containing structurally diverse N-alkyl substituents as potential glycosidase and glycosyltransferase inhibitors. By employing the click chemistry methodology, various synthetically accessible aliphatic and aromatic azides were conjugated to the acetylene-functionalised 6- and 7-membered ring N-propynyl azasugar scaffolds using click chemistry, thus providing expedient access to N-methylene triazole-substituted azasugars in a single, high yielding step. The work demonstrates the applicability of the reaction for generating not only the structural diversity deemed necessary for distinguishing inhibitory potency and selectivity, but also a powerful means of tuning the physicochemical properties of the azasugar for in vivo targeting and lead optimisation purposes.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Biomolecular and Physical Sciences<br>Full Text
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Salwiński, Aleksander. "Development of novel mass spectrometry-based approaches for searching for low-mass tyrosinase inhibitors in complex mixtures." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2013/document.
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Ce manuscrit de thèse présente le développement de méthodes basées sur la spectrométrie de masse consacrées à la recherche d'inhibiteurs d'enzymes en milieux complexes, tels que les extraits de plantes. L’enzyme Tyrosinase a été utilisé comme principale cible biologique du fait de son implication dans les processus d’hyperpigmentation cutanée. De ce fait, la recherche d’inhibiteurs de cette enzyme, présente un grand intérêt pour l'industrie cosmétique. La première partie de ce manuscrit décrit la mise en place de la chromatographie d'affinité frontale (FAC), permettant d’obtenir le classement simultané des inhibiteurs présent dans un mélange complexe en fonction de leurs affinités avec la cible biologique. Deux capillaires hydrophiles de phase monolithiques ont été évalués afin de réduire au maximum les interactions non spécifiques indésirables entre les analytes et le support solide d’immobilisation. De plus, nous avons étudié la faisabilité de l’utilisation de phases à base de silice comme support solide d’immobilisation des enzymes dans le cadre de ces analyses par chromatographie d'affinité frontale. La seconde partie du manuscrit de thèse est consacrée au développement et à l’optimisation de l’approche nommée ENALDI-MS (Enzyme-coupled Nanoparticles-Assisted Laser Desorption/Ionisation Mass Spectrometry) permettant d’accéder à une gamme des faibles masses (m/z 500 Da). Elle est déclinée en une première approche dite par ‘extinction d’ions’ (Ion Fading, IF-ENALDI), basée sur l’identification directe de la liaison des inhibiteurs vis-à-vis de l’enzyme sans pré-traitement de l’échantillon végétal. Une seconde déclinaison de l’ENALDI-MS concerne une approche dite par ‘Ion Hunting’ (IH - ENALDI MS), basée sur une méthode de pré-concentration sélective des inhibiteurs présents dans l'échantillon<br>This thesis report presents the development of mass spectrometry-based methods for searching for inhibitors of enzymes in complex mixtures, such as plant extracts. Tyrosinase enzyme was used as the main biological target for the reason of a significant importance of its inhibitors in the cosmetic industry as the skin whitening agents. The first part of this report describes Frontal Affinity Chromatography (FAC), an approach enabling simultaneous ranking the inhibitors within the complex mixture according to their affinities to the biological target. Two hydrophilic capillary-scale polymer-based bioaffinity stationary phases were evaluated in the context of the presence of undesirable nonspecific interactions between the analyte and the solid immobilisation support. In addition, we explored the usability of two types of silica-based particles as a solid support for enzyme immobilisation for FAC. The second part of the thesis manuscript is devoted to Enzyme-coupled Nanoparticle-Assisted Laser Desorption/Ionisation Mass Spectrometry (ENALDI MS) as a low-mass compatible extension of the Intensity ion Fading MALDI MS (IF-MALDI MS) method for high-throughput screening of the inhibitors in the complex mixtures. Two variations of ENALDI MS were evaluated: 'Ion Fading' (IF-ENALDI MS), based on on-the-spot binding of inhibitors by enzyme molecules and 'Ion Hunting' (IH-ENALDI MS), based on selective pre-concentration of inhibitors present in the sample
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Daneshpour, Nooshin. "Local and systemic delivery of a novel group of inhibitors of transglutaminase enzyme : a potential approach for treating of catheter-related complications and liver fibrosis." Thesis, Aston University, 2010. http://publications.aston.ac.uk/13343/.
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The present thesis investigates targeted (locally and systemically) delivery of a novel group of inhibitors of enzyme transglutaminases (TGs). TGs are a widely distributed group of enzymes that catalyse the formation of isopeptide bonds between the y-carboxamide group of protein-bound glutamines and the a-amino group of protein-bound lysines or polyamines. The first group of the novel inhibitors tested were the tluorescently labelled inhibitors of Factor XIIIa (FXIIIa). These small, non-toxic inhibitors have the potential to prevent stabilisation of thrombi by FXIIIa and consequently increase the natural rate of thrombolysis, in addition it reduces staphylococcal colonisation of catheters by inhibiting their FXIIIa¬mediated cross-linking to blood clot proteins on the central venous catheter (CVCs) surface. The aim of this work was to incorporate the FXIIIa inhibitor either within coating of polyurethane (PU) catheters or to integrate it into silicone catheters, so as to reduce the incidence of thrombotic occlusion and associated bacterial infection in CVCs. The initial work focused on the incorporation of FXIIIa inhibitors within polymeric coatings of PU catheters. After defining the key characteristics desired for an effective polymeric-coating, polyvinylpyrrolidone (PVP), poly(lactic-co-glycolic acid) (PLGA) or their combination were studies as polymers of choice for coating of the catheters_ The coating was conducted by dip-coating method in a polymer solution containing the inhibitor. Upon incubation of the inhibitor-and polymer-coated strips in buffer, PVP was dissolved instantly, generating fast and significant drug release, whilst PLGA did not dissolve, yielding a slow and an insufficient amount of drug release. Nevertheless, the drug release profile was enhanced upon employing a blend solution of PVP and PLGA. The second part of the study was to incorporate the FXIIIa inhibitor into a silicone elastomer; results demonstrated that FXIIIa inhibitor can be incorporated and released from silicone by using citric acid (CA) and sodium bicarbonate (SB) as additives and the drug release rate can be controlled by the amount of incorporated additives in the silicone matrix. Furthermore, it was deemed that the inhibitor was still biologically active subsequent to being released from the silicone elastomer strips. Morphological analysis confirmed the formation of channels and cracks inside the specimens upon the addition of CA and SB. Nevertheless, the tensile strength, in addition to Young's modulus of silicone elastomer strips, decreased constantly with an increasing amount of amalgamated CA/ SB in the formulations. According to our results, incorporation of FXIIIa inhibitor into catheters and other medical implant devices could offer new perspectives in preventing bio-material associated infections and thrombosis. The use of tissue transglutaminase (T02) inhibitor for treating of liver fibrosis was also investigated. Liver fibrosis is characterized by increased synthesis and decreased degradation of the extracellular matrix (ECM). Transglutaminase-mediated covalent cross-linking is involved in the stabilization of ECM in human liver fibrosis. Thus, TG2 inhibitors may be used to counteract the decreased degradation of the ECM. The potential of a liposome based drug delivery system for site specific delivery of the fluorescent TG2 inhibitor into the liver was investigated; results indicated that the TG2 inhibitor can be successfully integrated into liposomes and delivered to the liver, therefore demonstrating that liposomes can be employed for site-specific delivery of TG2 inhibitors into the liver and TG2 inhibitor incorporating liposomes could offer a new approach in treating liver fibrosis and its end stage disease cirrhosis.
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Stimac, Robert. "Macrocyclic carbon suboxide derivates : novel potent inhibitors of the Na,K-ATPase, and their mechanism of inhibition = Makrozyklische Kohlensuboxid-Derivate : neuartige, besonders wirksame Inhibitoren der Na,K-ATPase und ihr Inhibitionsmechanismus /." Konstanz, 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=974308676.
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Shahid, Imran. "Synthesis and biochemical evaluation of novel non-steroidal inhibitors of the cytochrome P450 enzyme 17α-hydroxylase/17,20-lyase in the treatment of hormone-dependent prostate cancer". Thesis, Kingston University, 2008. http://eprints.kingston.ac.uk/20397/.
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A high proportion of prostate cancers have been shown to be androgen-dependent. The biosynthesis of the androgens is catalysed by the cytochrome P450 enzyme 17[alpha]-hydroxylase/17, 20-lyase (P450[sub]17[alpha]), which is responsible for the conversion of C[sub]21 steroids (for example pregnenolone and progesterone) to the androgens (for example dehydroepiandrosterone and androstenedione respectively). The inhibition of this enzyme would therefore lead to the overall reduction in the level of androgens and thus result in an overall decrease in the stimulation of androgen-dependent cancer cells. The compounds synthesised within the current study were designed such that the compounds were able to donate a lone pair of electrons to the Fe atom within the haem group of the active site of P450[sub]17[alpha]. As such, compounds based on benzyl imidazole backbone were synthesised as the major range of compounds with a small number of phenyl alkyl imidazole based compounds synthesised in an effort to evaluate physicochemical factors such as hydrophobicity. In general, the results of the study show that of the benzyl imidazole-based compounds were weak inhibitors of P450[sub]17[alpha] in comparison to the standard compound, namely ketoconazole (3) (IC[sub]50=1.66[plus or minus]0.15[mu]M against 17,20-lyase and IC[sub]50=3.76[plus or minus]0.01[mu]M against 17[alpha]-hydroxylase). The most potent benzyl imidazole-based compounds synthesised were: 4- iodobenzyl imidazole (224) (IC[sub]50=1.58[plus or minus]0.17[mu]M against 17,20-lyase and IC[sub]50=10.06[plus or minus]0.96[mu]M against 17[alpha]-OHase); 1-(3,4-dichloro-benzyl)-1H-imidazole (215) (IC[sub]50=2.07[plus or minus]0.07[mu]M against 17,20-lyase and IC[sub]50=12.22[plus or minus]0.88[mu]M against 17[alpha]-hydroxylase); 1-(3,5-dichloro-benzyl)-1H-imidazole (216) (IC[sub]50=3.34[plus or minus]0.11[mu]M against 17,20-lyase and IC[sub]50=22.56[plus or minus]0.34[mu]M against 17[alpha]-hydroxylase); 1-(3,5-dibromo-benzyl)-1H-imidazole (221) (IC[sub]50=3.16[plus or minus]0.11[mu]M against 17,20-lyase and IC[sub]50=25.95[plus or minus]0.91[mu]M against 17[alpha]-hydroxylase). The phenyl alkyl imidazole based compounds were found to be more potent than the benzyl imidazole-based compounds and 3 and included: phenylheptyl imidazole (318) (IC[sub]50=0.10[plus or minus]0.02[mu]M against 17,20-lyase and IC[sub]50=0.32[plus or minus]0.05[mu]M against 17[alpha]-hydroxylase); phenyloctyl imidazole (321) (IC[sub]50=0.21[plus or minus]0.02[mu]M against 17,20-lyase and IC[sub]50=0.25[plus or minus]0.01[mu]M against 17[alpha]-hydroxylase); and phenylnonyl imidazole (324) (IC[sub]50=0.35[plus or minus]0.01[mu]M against 17,20-lyase and IC[sub]50=1.06[plus or minus]0.03[mu]M against 17[alpha]-hydroxylase). Consideration of the structure-activity relationship determination and the molecular modeling of the synthesised compounds using the substrate-haem complex (SHC) approach shows that the disubstituted derivatives of benzyl imidazole were able to utilise both hydrogen bonding groups which are presumed to exist at the active site of P450[sub]17[alpha]. These compounds were found to be considerably more potent than the mono-substituted derivatives, as such, it suggests that the increase in the number of interactions between the inhibitor and the enzyme is the key feature which results in the increase in potency. The inhibitory data obtained for the phenyl alkyl imidazole-based compounds show that hydrophobicity (logP) of the inhibitor plays a major role in determining the overall inhibitory activity of these compounds. As such, the study suggests that in the design of further novel inhibitors of this enzyme, the interaction with the active site and logP are two factors which would allow for the synthesis of highly potent inhibitors of this enzyme.
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Slynko, Inna [Verfasser], Wolfgang [Akademischer Betreuer] Sippl, Mike [Akademischer Betreuer] Schutkowski, and Gerhard [Akademischer Betreuer] Wolber. "Structural analysis and computer-based design of novel inhibitors for human protein-kinase-C-related enzyme PRK1 / Inna Slynko. Betreuer: Wolfgang Sippl ; MIke Schutkowski ; Gerhard Wolber." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2015. http://d-nb.info/1076503179/34.
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Pont, Masanet Caterina. "Multitarget strategies in search of novel drug candidates against Alzheimer’s disease." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/668672.
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Alzheimer’s disease (AD) is the most common form of dementia and one of the most important health-care problems in the world, due to its high prevalence and unaffordable personal and economic impact. Moreover, current commercialised treatments are only symptomatic, but are not capable of preventing, curing or even delaying the disease progression. Because AD arises from a complex network of pathological events, such as dysfunction in neurotransmitter systems (mainly cholinergic and glutamatergic), β-amyloid and tau proteins disorders, oxidative stress or neuroinflammation, amongst others, the traditional medicinal chemistry paradigm of “one molecule-one target” is increasingly regarded as clearly ineffective. On the contrary, it becomes evident that a more comprehensive, complex pharmacological approach is needed to tackle AD. As a consequence, the use of multitarget directed ligands, where one single molecule is able to interact simultaneously with multiple targets of the pathological network, is emerging as a promising and more realistic way to confront this disease. In this context, the purpose of the present Thesis was the design, synthesis and biological evaluation of three novel families of compounds, endowed with multitarget biological profile, in order to find novel treatments for AD: 1) firstly, a new series of compounds designed by substitution of the rhein subunit of a rhein–huprine hybrid lead, previously developed in our group, by more simplified scaffolds, with the aim of finding optimized hybrids with reduced lipophilicity and better drug-like properties, while maintaining favourable activities against cholinesterases, BACE1, β- amyloid and tau aggregation, and antioxidant properties; 2) secondly, a novel family of huprine- derived hybrids, designed to perform a dual binding site interaction within BACE1 through the linkage of a huprine moiety to new scaffolds, selected by their predicted binding affinities towards a secondary transient pocket in BACE1, which were expected to combine cholinesterases and BACE1 inhibitory activities, as well as activity against β-amyloid and tau aggregation, and antioxidant properties; 3) finally, a family of huprine–TPPU and tacrine–TPPU hybrids, which were designed to be dual inhibitors of acetylcholinesterase (AChE) and soluble epoxide hydrolase (sEH). The blood–brain barrier permeability was also assessed for all these compounds, as it is a crucial factor for drugs acting in the central nervous system, while other important physicochemical and pharmacokinetic parameters, such as solubility and microsomal stability were determined for the latter series of compounds. Also, the toxicity of some compounds was evaluated. Finally, using the same assay that was employed for the determination of the β-amyloid and tau antiaggregating activity of the first two families and other compounds synthesised by our group, we demonstrated that a single compound can be able of inhibiting the aggregation of different types of amyloid-prone proteins, with these results supporting the notion that common mechanisms exist for the aggregation of different amyloidogenic proteins and that a generic treatment of conformational diseases is possible.
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Evitt, Andrew. "Design, Synthesis & Evaluation of Inhibitors & Substrates of the Enzyme L-Aspartate-/B-Semialdehyde Dehydrogenase AND A Novel Synthetic Route to Deoxyxylulose-5-Phosphate - a Substrate of Deoxyxyluiose-5-Phosphate Reductase." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520640.
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Yang, Chou-Chih, and 楊宙芝. "Structure-based screening on novel potent inhibitors for Prephenate Dehydratase (PDT) of Buchnera aphidicola." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/69909665781183100620.
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碩士<br>國立彰化師範大學<br>生物學系<br>97<br>Aphids are insect vectors which transmit virus and damage agricultural economy. Aphids feed strictly on the nutritionally poor diet of phloem sap by piercing-sucking mouthparts, and thus maintain an obligate endosymbiotic association with Buchnera aphidicola, a member of the class -Proteobacteria closely related to Escherichia coli. It is commonly accepted that Buchnera provides essential nutrients to aphids. The enzyme prephenate dehydratase (PDT) is encoded by pheA, and is a terminal and committed enzyme in the biosynthesis of L-Phe in the shikimate pathway. In different organisms, PDTs exist as either monofunctional or multifunctional enzymes. Generally, in Gram-positive bacteria and archaea, PDT is a monofunctional enzyme. However, in Gram-negative bacteria such as E. coli and Buchnera aphidicola APS, PDT exits as a fusion protein with the enzyme chorismate mutase (CM) to form a bifunctional enzyme.
PDT converts prephenate to phenylpyruvate through dehydration and decarboxylation reactions, and is allosterically regulated by the end product L-Phe. The enzyme is only found in microorganisms, fungi, and plants, and is a novel and potential drug target. Hence, we hope to find more effective inhibitors of the Buchnera P-protein through structure-based virtual screening. These inhibitors can be used to reduce the viability of aphids by blocking the growth of Buchnera.
PDT consists of an N-terminal PDT domain (the catalytic domain) and a C-terminal ACT domain (the regulatory domain). The PDT domain contains the substrate (prephenate) binding site. The ACT domain in its dimeric form often binds the end product L-Phe or other amino acids, and produces a conformational change to regulate the activity. Important features of the ACT domain for L-Phe binding are the GALV and ESRP motifs, but in P-protein of Buchnera, the ESRP motif is changed to TSQK. For this reason, P-protein of Buchnera is proposed to be insensitive to feedback inhibition by L-Phe.
In the study, we built the E. coli and Buchnera homology models based on 2QMW, the first and the only native PDT crystal structure. Then, we used different scoring function from the molecular docking program, and analyzed the prephenate, DNBA and their analogs docking results. After the docking program parameter set up, we exercised a virtual screen for PDT inhibitors by docking molecules in IBS chemical databases to 2QMW. In the end, we chose twenty compounds according to their molecular weight, scoring rank, molecular docking pose, hydrophile group and structure heterology. Then, we to test their activity in vitro in the future.
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Teng, Lead-Well, and 鄧力瑋. "Virtual screening and 3D-QSAR study on novel potent inhibitors for nuclear factor kappa B." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/27473293793089737205.
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碩士<br>國立彰化師範大學<br>生物技術研究所<br>96<br>NF-κB (nuclear factor-kappa B) is an important transcription factor. It is found in almost all animal cell types and is involved in cellular responses to stimuli such as stress, ultraviolet irradiation, and bacterial or viral antigens. NF-κB plays a key role in regulating the immune response to infection. Consistent with this role, incorrect regulation of NF-κB has been linked to cancer, inflammatory and autoimmune diseases, septic shock, viral infection, and improper immune development. Therefore, we report selective inhibitor of NF-κB activation expected was able to therapeutic approach to inflammatory disease. In order to elucidate the 3D quantitative structure-activity relationship of NF-κB inhibitors was developed based on 35 potent inhibitors by CATALYST and PHASE software. The best scoring pharmacophore hypothesis, Hypo1, consisting of five features, had a best correlation coefficient of 0.9088. In the test set analysis, a correction coefficient of 0.83586 shows a good correlation between the experimental and estimated activities. In addition, a PHASE 3D-QSAR model derived with this pharmacophore yielded an R-squared of 0.9705 and an excellent external test set predictive R-squared of 0.8126 for 18 compounds. It is demonstrated that the performance of Phase is better than or equal to that of Catalyst HypoGen. The best CoMSIA model was identified from the stepwise analysis results and constructed a pharmacophore of the training set correspond to derived CoMSIA model were used by the Catalyst program. The best scoring pharmacophore hypothesis, Hypo1, consisting of six features, had a best correlation coefficient of 0.9032. In the test set analysis, a correction coefficient of 0.76. Furthermore, the pharmacphore features were correctly mapped onto structure surface. The results of our study provide a valuable tool in designing new leads with desired biological activity by virtual screening. Finally, we continued to search Maybridge database by pharmacophore-based virtual screening, and found 7 compounds, at last select most potential lead compound by docking software, could be continue in vitro assay.
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Bhuyan, Bhaskar Jyoti. "Design And Synthesis Of Novel Angiotensin Converting Enzyme (ACE) Inhibitors Having Antioxidant Activity." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1339.
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Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (AngII). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to its inactive form. Therefore, inhibition of ACE is one of the treatments of hypertension. A number of ACE inhibitory antihypertensive drugs are known. ‘Oxidative stress’ is another disease state caused by an imbalance in the production of oxidants and antioxidants in the body. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension.
Generally, selenium compounds exhibit better antioxidant behavior than their sulfur analogues. Therefore, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as antihypertensive drug. Similar to captopril, the selenium analogues of captopril exhibited excellent ACE inhibition property. It was observed that these compounds are very good scavengers of peroxynitrite (PN), a strong oxidizing as well as nitrating agent found in vivo. The orientation of the chiral centers in these compounds was found to be very important for their ACE inhibition behavior.
A number of selenocysteine- and cysteine-containing dipeptides and tripeptides were synthesized as inhibitors of ACE. It was observed that the ACE inhibition properties of these compounds depend on various factors such as orientation of the amino functionality, substitution at the C-terminal of the inhibitor, ring size of the proline moiety or the availability of the terminal acid group in carboxylate form etc. A structure-function correlation was drawn for the ACE inhibition properties of the peptide-based selenium-or sulfur-containing compounds. These studies reveal that the antioxidant properties do not depend on the side-chain functional groups, but they depend on the availability of selenium or sulfur centers. Selenium-based compounds were found to be better antioxidants than those containing sulfur moieties. In conclusion, the present study reveals that the replacement of sulfur atom in captopril and its analogues by selenium enhances the antioxidant activity.
The reaction products of lactoperoxidase (LPO)-catalyzed iodination of Ang II were separated and characterized. It was observed that LPO-catalyzed iodination of Ang II takes place preferentially at the tyrosine residue. LPO-catalyzed iodination of Ang II is inhibited by commonly used antithyroid drugs such as MMI, MTU, PTU and also by antihypertensive drug captopril. It was also observed that the monoiodo Ang I is a better substrate for ACE compared to the natural substrate Ang I. The site of nitration of Ang II by PN was also determined by MS-MS analyses. This study reveals that the nitration takes place at the tyrosine residue.