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Bihari, Shailja. "Bio-inorganic chemistry of manganese and titanium." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/9995.
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A wide range of metals are transported in the body by the protein transferrin, including both essential metal ions and probably also metals used in therapeutic agents. The metal binding sites on transferrin contain tyrosine, histidine and aspartate ligands. This thesis is concerned with studies of the essential metal ion manganese, and with titanium, which is used in anticancer agents. In order to aid the characterisation of Mn(III) and Ti(IV) transferrins, the Mn(III) and Ti(IV) complexes with the model ligand ethylenebis[(a-hydroxyphenyl)glycine](H₄EHPG) have been studied. The Mn(III) complexes rac-Na[Mn(EHPG)].3H₂0 (1) and rac,mesoNa[Mn(EHPG)].H₂0 (2), have been prepared and their X-ray crystal structures determined. Complex 1 contains N(S,S)C(R,R) configurations at the N and C stereogenic centres, whilst in the unit cell of complex 2 there are two independent molecules, 2a (mesa) and 2b (rac), with N(R,R)C(S,R) and N(R,R)C(S,S) configurations, respectively. Enantiomers of each complex are also present. The Mn(III) centres have Jahn-Teller-distorted octahedral geometry, with two long bonds and four short bonds. ¹H NMR spectra of these high-spin d⁴ paramagnetic complexes are reported. These complexes give rise to similar ligand (phenolate)-tometal charge-transfer bands as Mn(III)-transferrin. Dissociation of Mn(III) from EHPG occurs below pH 3.4. The Ti(IV) complex of rac-[Ti(EHPG)(H₂0)].1113H₂0 (3) has also been prepared and the X-ray crystal structure determined. All previously-reported crystalline racEHPG metal complexes contain N(S,S)C(R,R), or N(R,R)C(S,S) isomers, whereas 3 unexpectedly contains the N(S,S)C(S,S) and N(R,R)C(R,R) forms. 2D NMR studies indicate that 3 has a similar structure in solution to that in the solid state. A ligand (phenolate)-to-metal charge transfer band was observed at 386 nm, similar to that seen for Ti(IV)-transferrin. Ti(IV)EHPG was stable at pH values down to 1, however, the complex decomposed above pH 7. Mn(III)-transferrin complexes were prepared by air oxidation of Mn(II) in the presence of transferrin. The oxidation state of manganese bound to transferrin was Abstract confirmed by K edge EXAFS. Analysis of the EXAFS data revealed that the metal centre is also Jahn-Teller distorted but with four long bonds and two short bonds, i.e. an inverse distortion to that seen in the Mn(III)EHPG model complexes. Attempts to prepare other Mn(III) complexes which might be suitable for studies of Mn transfer to proteins are described and include cyclam and bicyclam as ligands. The crystal structure of [Mn(cyclam)Ch]Cl₂H₂0 was determined, and contained two long axial Mn-Cl bonds of 2.5249 Å. This complex was shown by electronic absorption spectroscopy to undergo a complicated series of reactions in aqueous solution. K edge EXAFS measurements suggested that at least one Cl ligand dissociated from the complex in aqueous solution. The hydrolysis was shown to be inhibited by the presence of fluoride.
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Mantri, Yogita. "Computational modeling of transition metals in medicinal chemistry realistic models to probe metal-biomolecule binding energetics /." [Bloomington, Ind.] : Indiana University, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3386701.
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Thesis (Ph.D.)--Indiana University, Dept. of Chemistry, 2009.Title from PDF t.p. (viewed on Jul 22, 2010). Source: Dissertation Abstracts International, Volume: 70-12, Section: B, page: 7549. Adviser: Mu-Hyun Baik.
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Freeman, Thomas L. "Folding and redox-linked conformational switching of the Geobacter heme sensor GSU0935." Thesis, Dartmouth College, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=1550957.
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Heme-based redox sensors are implicated in a number of important physiological processes such as nitrogen fixation, aerotaxis, and control of circadian cycles. These proteins often rely on proper ligand switching for functional activation. It is unclear how a protein's conformation in many of these heme-based sensors affects ligation at the heme and vice versa. GSU0935, a methyl-accepting chemotaxis sensor protein from Geobacter sulfurreducens, contains a periplasmic binding domain (PBD) with a c-type heme. Previous reports indicated that the heme iron switches its axial ligands from water to Met60 upon heme reduction. The heme iron ligation in the GSU0935 PBD was investigated in chemically-denatured protein samples to characterize the relationship between protein conformation and heme ligation using UV-visible absorbance spectroscopy. A red shift in the Soret band of GSU0935 was linked to misligation by deprotonated His169 at physiological pH under denaturing conditions. Stopped-flow studies showed that protein refolding results in rapid dissociation of His169 to be replaced by His54 as the distal heme ligand. His54 misligation acts as a kinetic trap during protein refolding and slows the formation of the native water-ligated heme. These results suggest that the heme domain of GSU0935 has a highly flexible N-terminal region and an exposed heme environment, which may be important for sensory function.
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Zierden, Mark Robert. "Towards Understanding the Trafficking and Function of Iron and Titanium Ions in Organisms." Diss., Temple University Libraries, 2016. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/421398.
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ChemistryPh.D.
It is estimated that up to one third of all proteins are metalloproteins. These proteins have evolved to use the metals that are, or at least were at the time of their initial evolution, the most accessible. Some active centers of metalloenzymes resemble the structures of minerals presumed to be present in precipitates from hydrothermal solutions in the ocean billions of years ago. The metals in these proteins serve myriad purposes from structure to transport to catalysis. For these purposes organisms must find a way to incorporate, transport and possibly store the metal ions from the environment. Iron, among other metals, is used for all the before mentioned purposes but in oxic aqueous conditions is hydrolysis prone. Depending on its oxidation state iron is either insoluble or reacts to form reactive oxygen species and is dangerous to organisms. Organisms have thus evolved complex mechanisms to overcome the challenges of trafficking hydrolysis prone metals. This dissertation will focus on the study of the trafficking of hydrolysis prone iron and titanium by organisms, from metal selection to their use and storage. An examination of why metals are chosen, sequestration and transport of these metals, and use of the metals is presented. This research, as a whole, explores the cellular life cycle of hydrolysis prone metals. It is thought that the first uses of metals before their incorporation by organisms were at mineral surfaces. To this end it would be useful for the organism to be able to attach to the mineral surface. Rhodococcus ruber GIN-1 was isolated for its ability to selectively bind to TiO2 over other metal oxides. Biologically it could be advantageous to selectively bind to one mineral surface over another. The isolation and identification of these proteins are examined within. Rhodococcus ruber GIN-1 has also been found to produce a novel siderophore. The siderophore is not yet completely identified but falls into the class of catecholates. Once organisms begin to incorporate and use metals in proteins it would be useful to sequester and concentrate necessary metal ions that exist in low concentration in their environment. There are multiple organisms that are known to sequester high levels of titanium. One relatively unexplored family is that of Sabellidae or the feather duster worm. Organisms like this have been proposed as sentinel organisms to detect metal pollution in waters. In a model Sabellidae organism we have detected elevated levels of titanium, among other metals. After metal sequestration from the environment, intraorganism transport of the ions to where they are necessary becomes important. Higher organisms use the transferrin family of proteins to traffic iron. While the transferrin cycle has been studied in depth, the reduction mechanism has not been elucidated in detail. We use a monolobal transferrin, nicatransferrin, from the model organism Ciona intestinalis to explore this iron reduction mechanism of the transferrin cycle and find that nicatransferrin can reduce iron with no external reductant. This reduction occurs on the timescale expected for the transferrin cycle and occurs without an iron (II) chelator. The source of the reducing equivalent is unknown but nicatransferrin was measured to have reduced up to 2.5 equivalents of iron. Once transported to cells the metal ions can be put to use and incorporated into proteins or other structures. We examine the possible intentional use of titanium as a pigment in Eudistoma purpuropuntatum. The most abundant titanium sequesterer known is Eudistoma ritteri, who concentrates titanium up to 1500 ppm (dry weight). Eudistoma purpuropunctatum, a close relative of Eudistoma ritteri, displays an interesting purple color due to small granules in its tunic. We investigate the source of the purple color in these granules and the ability of the organism to sequester titanium, finding that it has titanium concentrations on par with Eudistoma ritteri. The metal ions that are not put to immediate use can be stored. Some metals exist in labile pools but due to iron’s reactivity it is necessary to store it where it cannot cause cellular damage. The iron storage protein ferritin is a cage-like polymer made up of 24 ferritin monomers. The monomers exist as either H-chain or L-chain and the 24-mer can be comprised of just one type of these monomers or a mixture thereof. The covalent dimerization of the human L-chain 24-mer has been observed and the cause of this dimerization explored. We do not find direct evidence of the covalent linkage but do identify regions of the protein most likely to participate in the dimerization.
Temple University--Theses
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Alexander, Jessica L. "Characterization of Catalytic Metallodrugs: Advances towards Novel Antibiotics." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503313186810767.
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Sabo, Michael J. "Tapping mode analysis of lambda-DNA and carboplatin interactions." Thesis, Southern Illinois University at Edwardsville, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1600964.
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The purpose of this research was to examine the complexation of carboplatin and λ-DNA via atomic force microscopy. This project had the challenge of getting the necessary resolution which lead to the need to examine and improve upon the experimental protocol. These resolution issues were fixed by eliminating contamination, and by developing more consistent means of DNA application. The carboplatin and DNA complexation was then able to be observed. Initial indications are consistent with expectations because the DNA appears to become more condensed over time but further examination is required.
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Di, Pasqua Anthony J. "Carboplatin Exploring mechanism of action and improved drug delivery 1. Role of carbonate in the mechanism of action of carboplatin 2. Cytotoxicity of mesoporous silica nanomaterials /." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.
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Joshi, Hemant K. "Synthetic, structural, spectroscopic and computational studies of metal-dithiolates as models for pyranopterindithiolate molybdenum and tungsten enzymes: Dithiolate folding effect." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280480.
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Coordination by an axial oxo and an equatorial ene-dithiolate group is a salient feature of the active sites of the mononuclear pyranopterin Mo/W enzymes. Discrete mononuclear model complexes encompassing these features are important in understanding the metal-ligand interactions in these active sites. The compounds (Tp*)ME(S-S) (M = Mo, W; E = O, NO) and Cp₂M(S-S) (M = Ti, Mo, W) (where Tp* is hydrotris(3,5-dimethyl-1-pyrazolyl)borate, Cp is η⁵-cyclopentadienyl, S-S represents a generic ene-1,2-dithiolate ligand for example 1,2-benzenedithiolate and 3,6-dichloro-1,2-benzenedithiolate) provide access to three different electronic configurations of the metal, formally d¹, d² and d⁰, respectively. These compounds also allow the study of two metal, two axial ligand and two equatorial ene-dithiolate perturbations. X-ray crystallography, density functional theory and photoelectron spectroscopy are utilized to understand the metal-sulfur interaction in the above complexes. Subtle differences in the geometry of these compounds are observed, including the metal-dithiolate fold angle which is sensitive to the electronic occupation of the metal in-plane orbital. This orbital is presumably the "host" orbital to the electrons during catalysis. The work in this area has resulted in the development of a dithiolate-folding-effect. This effect relates to the experimental verification of the Lauher and Hoffmann bonding model for the metal-dithiolate interaction in these complexes. This "dithiolate-folding-effect" is proposed to account for the electronic buffering at the metal center. This effect may provide a regulatory mechanism for the metal-sulfur interactions and could be a factor in the electron transfer reactions that regenerate the active sites of molybdenum and tungsten enzymes. The structure and properties of these compounds are correlated with those of the enzyme active sites.
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Oram, Paul Daniel 1963. "The potentiometric determination of the formation constants of a novel class of macrocyclic polyaminocarboxylic acid ligands and the formation constants of the mercury(II)-glutathione complexes." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290597.
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Potentiometric titrations were used to determine the thermodynamic formation constants of the complexes of newly synthesized macrocyclic polyaminocarboxylic acid ligands with selected metal ions. The formation constants were calculated with the help of a computer modeling program, BEST. Protonated complexes and hydroxylated complexes often coexist with the neutral complex in certain pH regions. This formation of multiple species is an important consideration in putting these ligands to practical use. It was also found that some of the complexes undergo a change in geometry when the pH of the solution is changed from acidic to basic. Electron spin resonance and UV-visible spectra confirmed these changes. The formation constants of the mercury(II)-glutathione complexes were also determined by potentiometric titrations. It was found that the previously reported value was incorrect by approximately ten orders of magnitude. The formation constants of the secondary species were also determined. These values have not been reported previously. A complete understanding of the solution chemistry of these complexes should be beneficial for understanding the metabolism of mercury(II) in living organisms.
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Williams, Wesley S. "Method development for long-term monitoring of heavy metals in mussel shells by laser-ablation inductively-coupled-plasma mass-spectrometry." Thesis, The University of Tulsa, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3622730.
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Heavy metal pollution is a growing concern as growing worldwide population and industrial processes increase pollution levels in most environments. High metal concentrations throughout ecosystems pose a serious threat to wild-life and human health. Methods to monitor rising threat levels of metals are a primary concern for monitoring overall ecosystem health. Mechanisms which spread pollution must be intimately understood because of the persistence of heavy metals. Heavy metal contamination in the Tar Creek superfund site provides a great case study to selectively observe differences in heavy metals concentrations both upstream and downstream of mining activity. Thus, research is able to identify natural and man-made point sources of pollution.
The abilities of bivalves to filter-feed and sediment-feed provide a unique monitoring tool for analyzing heavy metals. Mussels are constantly filtering the environment around them. A mussel's seasonal and annual growth layers provide an excellent sample media for obtaining historical records of environmental data. Many species of mussels are found in most freshwater ecosystems throughout the United States. Mussels have low migration rates, live for a suitable amount of time, and leave relic shells. These features make mussels very practical for monitoring heavy metal pollution.
Various studies were conducted to obtain insight into developing methods for using LA-ICP-MS as a tool for monitoring heavy metals in mussel shells. Surface laser ablations, compared at additional depths, resulted in a more than 20% increase in signal intensity. Theoretical and experimental designs show signal changes as a function of depth. Mussel tissue and shell digestions were found to be best when using approximately 1.0 mL of hydrogen peroxide and 1.0 mL of nitric acid for each 0.1 grams of sample. Mussel tissue was found to have greater heavy metal concentrations than shells. Shells were found to average a 96% weight of calcium carbonate; however, the organic layers contained the greatest concentrations of heavy metals per weight.
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Stein, Natalia. "Spectroscopic and electrochemical studies of Shewanella oneidensis cytochrome c nitrite reductase, and improving c-heme expression systems." Thesis, The University of Wisconsin - Milwaukee, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3685085.
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In this work the redox properties of cytochrome c nitrite reductase (CcNiR), a decaheme homodimer that was isolated from S. oneidensis, were determined in the presence and absence of the strong-field ligands cyanide and nitrite. Four hemes per CcNiR protomer are hexa-coordinate with tightly bound axial histidines, while the fifth (active site) has one tightly bound lysine and a distal site that can be open, or contain exogenous ligands such as the substrate nitrite. Controlled potential electrolysis in combination with UV/visible absorption (UV-vis) and electron paramagnetic resonance (EPR) spectroscopies allowed for assignment of all heme midpoint potentials under each set of conditions. The studies show that the active-site heme is the first to be reduced under all conditions. The midpoint redox potential of that heme shifts approximately 70mV to the positive upon binding a strong field ligand such as nitrite or cyanide. When controlled potential electrolysis was carried out in the presence of nitrite, a concerted two electron reduction was observed by UV-vis, and a {Fe(NO)}7 reduced product was revealed in EPR. In addition, an asymmetry in ligand binding between active sites was revealed. This information is relevant for the interpretation of planned and ongoing mechanistic studies of CcNiR.
Over-expression, partial purification and characterization of another S. oneidensis multiheme enzyme, known as octaheme tetrathionate reductase (OTR), is also described herein. Though of unknown cellular function, OTR was previously reported to have tetrathionate reductase activity, in addition to nitrite and hydroxylamine reductase activities. The new results indicate that the expression of OTR has no effect on tetrathionate or nitrite reductase activities in the whole cell lysate, and only hydroxylamine reductase activity was substantially elevated in the overexpressing bacteria. OTR was stable in buffered solutions, but substantial activity loss during all attempts at column chromatography was a major obstacle to the complete purification. OTR also proved quite hydrophobic, so possible membrane association should be considered in future attempts to purify this protein.
Finally, this dissertation also reports attempts to improve S. oneidensis' ability to express foreign proteins. Though ideally suited to expressing c-hemes, it proved difficult to express carboxy his-tagged proteins in S. oneidensis because of persistent tag degradation. Attempts to knock out lon protease, a cytoplasmic carboxypeptidase, as well as the result of redirecting ccNiR from the SecA to the possibly more protected signal particle recognition (SRP) secretion pathway, are described.
Iron heme cofactors are single-electron transport moieties that play a crucial role in respiration. While oxygen is the electron acceptor of choice in aerobic atmospheres, microorganisms that live in anaerobic environments utilize other molecules with similarly high reduction potentials. S. oneidensis can utilize numerous terminal electron acceptors, including nitrite, dimethylsulfoxide and even uranium, thanks to a particularly rich array of multi c-heme respiratory proteins. Understanding of how the midpoint potentials and heme arrangements within the proteins influence these exotic respiratory processes is of interest in the fields of bioremediation and fuel development.
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Lutterman, Daniel Aaron. "Investigation of transition metal complexes with potential photochemical applications." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1184601514.
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Chapman, Erich G. 1984. "Platinum coordination to RNA." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11072.
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xix, 111 p. : ill. (some col.)Since discovery of its biological effects in the late 1960's, cisplatin (cis-diamminedichloroplatinum( II)) has become one of the most broadly-prescribed cancer drugs in use today. A majority of efforts to understand the metallobiochemistry of this drug have focused on describing the interactions of cisplatin-derived Pt(II) complexes with DNA. Drug binding to this "high value" cellular target is believed to trigger the apoptotic pathways that underlie cisplatin's cytotoxic effects. Although RNA is chemically similar to DNA and responsible for accurately transferring, regulating, and transforming the same genetic information that is stored within the DNA genome, surprisingly little is known about platinum(II) drug binding to RNA. Accordingly, the first three chapters of this dissertation describe efforts to address questions regarding cisplatin coordination to RNA on the molecular scale. Chapter I reviews fundamental aspects of how metal complexes interact with nucleic acids, highlighting the bioinorganic chemistry of platinum(II) antitumor drugs. This chapter also introduces the idea that drug binding to RNA may form an important part of how these complexes work in the cell. Chapter II describes cisplatin crosslinking between RNA nucleobases located on opposite sides of the internal loop of an RNA subdomain derived from the catalytic core of the spliceosome. Chapter III describes how platinum adducts disrupt the activity of RNA processing enzymes similar to those that are necessary for maturation, maintenance and recycling of the transcriptome. Chapter III also describes the reversal of RNA platination using thiourea. The chemistry of platinum(II) is also characterized by preferential coordination to sulfur ligands, or thiophilicity. Incorporating this property into RNA chemistry, Chapters IV and V describe the reaction of platinum(II) complexes with phosphorothioate-substituted RNAs. Chapter IV describes engineering platinum(II) crosslinks in the Hammerhead ribozyme through the targeting of a platinum(II) complex to a specific phosphorothioate substitution installed in the active site of this catalytic RNA. Chapter V outlines efforts to characterize the cleavage and isomerization reactions promoted by platinum(II) coordination to phosphorothioate-substituted RNAs. Finally, Chapter VI summarizes the insights gained throughout the course of our studies and provides an outlook on the future of platinum-RNA chemistry. This dissertation includes co-authored material and previously published results.
Committee in charge: Michael M. Haley, Chair; Victoria J. DeRose, Advisor; David R. Tyler; Andrew J. Berglund; Eric A. Johnson
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Smith, Adam C. R. "The Effects of Carrier Ligands on Cisplatin Binding to Cysteine and Methionine." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1969.
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We have reacted several derivatives of the anticancer drug cisplatin with N-acetyl-Lcysteine (N-AcCys) and N-acetyl-L-methionine (N-AcMet), which are two of the primary amino acid targets of platinum. NMR spectroscopy was used to monitor the reactions and determine the effect the different ligands would have on the platinum reactivity. Several of the platinum compounds were tested at pH of 4 and 7, and with platinum:amino acid ratios of 1:1, 2:1 and 1:2. Competition reactions between cysteine and methionine were done to confirm which would react with the platinum compound first. [Pt(dien)(NO3)]+ reacts faster with methionine than with cysteine at both pH 4 and 7 at a 1:1:1 ratio. [Pt(N,N,N',N',N"-pentamethyldiethylenetriamine)(NO3)]+ reacts with methionine faster at pH 4 but with cysteine faster at pH 7. This is most likely due to the thiol in the cysteine starting to deprotonate around pH 7. [Pt(Me4en)(NO3)2] (Me4en = N,N,N',N'-tetramethylethylenediamine) forms several products with N-AcCys at both pH 4 and 7, with the amounts of the products varying depending on the ratio of platinum and Cys. Mass spectrometry indicated one product as {[Pt(Me4en)(H2O)]2(N-AcCys)}2+, with two platinum compounds coordinated to a single cysteine. Lastly Pt[(en)(NO3)2] when reacting with N-AcCys at a ratio of 1:1 will coordinate with 2 different Cys molecules. With an excess of Pt the complex prefers to bind to only 1 Cys.
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Binkley, Sarah L. "Re(I) Tri-Carbonyl Based Radiopharmaceuticals; Synthesis, in vitro Studies, and Protein Complexation." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1469473412.
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Bauman, Mariia A. "Characterizing the Effect of Conformational Changes in the Protein SufU on its Ability to Enhance Enzymatic Activity of the Cysteine Desulfurase SufS in Streptococcus mutans." Bowling Green State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1467906490.
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McDaniel, Alicia L. "Synthesis and Characterization of Bis-Phosphine Complexes with Transition Metals." TopSCHOLAR®, 2009. http://digitalcommons.wku.edu/theses/110.
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Extractants and extraction methodologies play a vital role in many industrial processes, from the concentration of precious metals from ores to the separation of longlived nuclei from radioactive waste as well as the removal of heavy metals from soils and water for remediation. The vast majority of extractants rely on the use of nitrogen, oxygen, sulfur or selenium as Lewis base donor atoms to form coordination complexes with the metal ions of interest. These extractants often make use of the chelate effect and/or the macrocyclic effect in order to form stable complexes. Some of the best known types of chelate extractants include polyaminopolycarboxylic acids (N and O donors), polyamines (N donors), dithiocarbamate (S donors) and aminopolythias (N and S donors). The most extensively investigated types of macrocycles include crown ethers (O donors), thia crowns (S donors), aza crowns (N donors) and thiacrown ethers (S and O donors).
A conspicuous omission from the list of donor atoms is phosphorus. It is noted that phosphorus has been employed as a backbone atom in the development of extractants, primarily in phosphonates, phosphates and phosphine oxides. The omission of phosphorus is interesting from two points. First, many of the precious and heavy metal ions of interest (Pd2+, Ag+, Pt2+, Pb2+, Cd2+and Hg2+) can be classified as soft Lewis acids, according to Pearson’s HSAB theory. The relative softness of phosphorus as a Lewis base as compared to oxygen and nitrogen indicates that phosphorus would be a very good donor atom toward these soft metal cations. Secondly, chelating agents containing phosphorus donors form stable complexes with transition metal cations in a variety of oxidation states due to their versatile bonding capability. The !-donor characteristics of the phosphine donor coupled with the ability to " accept from filled or partially filled d orbitals of the metal cations result in strong phosphine-metal bonds.
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Millay, Heidi Linn Hruska. "Leaving Ligand Effects on Reactivity and Solubility of Monofunctional Platinum(II) Anticancer Complexes." TopSCHOLAR®, 2019. https://digitalcommons.wku.edu/theses/3154.
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Monofunctional platinum(II) complexes, such as phenanthriplatin and pyriplatin, have notably different characteristics from the bifunctional anticancer complexes, such as cisplatin and oxaliplatin, which have detrimental toxicities and resistance associated with them. The unique properties of the monofunctional complexes may be exploited to target cancer cells without producing the toxic side effects associated with the current FDA-approved platinum-based anticancer drugs. To advance the understanding of these monofunctional platinum(II) complexes, this study replaced the chloride leaving ligand with an acetate group, which should increase solubility and alter the rate of reactivity with key amino acid and nucleotide targets. Phenanthriplatin and pyriplatin compounds were reacted with silver acetate to form insoluble silver chloride and the desired complex. Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to characterize the new complexes and conduct kinetic assays with guanosine 5'-monophosphate (5’-GMP). A rate constant of 2.9 (± 0.7) x 10-2 M-1s-1 was determined for the reaction between pyriplatin and 5’-GMP, previously. A preliminary rate constant of 1.8 (± 0.1) x 10-2 M-1s-1 was determined for the newly synthesized cis-[Pt(NH3)2(py)OAc]+ complex with 5’-GMP. Ligand exchange kinetics directly influences the anticancer activity and toxicity of platinum drugs. Initial results indicate that the solubility is increased, and the rate of reaction is decreased by the acetate ligand.
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Jeddi, Haleh. "Synthesis, Kinetic and Catalytic Studies of Manganese Complexes with Corrole and Porphyrin Ligands." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1949.
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High-valent transition metal-oxo intermediates play a significant role in the catalytic cycle of the ubiquitous cytochrome P450 enzymes and in biomimetic catalytic systems. In this work, manganese(III) porphyrin and corrole systems (2) were synthesized and characterized by UV-vis absorbance and 1H-NMR, matching literaturereported spectroscopic data. Manganese(V)-oxo corroles (3) and a manganese(IV)-oxo porphyrin (4) were successfully generated by chemical oxidation using mchloroperoxybenzoic acid (m-CPBA), and their oxidation reactions with organic reductants were comparatively investigated. Results from single-turnover kinetic studies indicate that in the tris(pentafluorophenyl)corrole system (3a), the active oxidizing intermediate differs in different solvents. The active oxidizing intermediate in acetonitrile is likely the manganese(V)-oxo species 3a. However, in dichloromethane, the active oxidant is suspected to be a putative manganese(VI)-oxo species generated by disproportionation of the manganese(V)-oxo species.
Tris(pentafluorophenyl)corrolato manganese(III) (2a) was shown to selectively catalyze sulfoxidation and epoxidation with iodobenzene diacetate [PhI(OAc)2] as a mild oxygen source. 2a exhibited higher conversions than triphenylcorrolato manganese(III) (2b), most likely because of the higher stability of 2a compared to 2b. In contrast, tetramesitylporphyrinato manganese(III) (2c) was more efficient in catalytic oxidations than 2a, resulting in much higher conversions, but much less selectivity. Other reported metalloporphyrin and metallocorrole systems show an accelerating effect upon addition of small amounts of water; however, neither corrole systems exhibited a positive water effect. This is attributed to the strong coordination between the manganese center and water, preventing the oxygen source from coordination.
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Damasceno, Marcos Oliveira. "Estrutura e reatividade de compostos de cobre(II) com ligantes diimínicos hidroxilados." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/46/46134/tde-12112018-161632/.
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Compostos dinucleares de cobre(II) com ligantes diimínicos hidroxilados, do tipo quelato, macrocíclico e macroacíclico, foram preparados visando um estudo comparativo de suas características estruturais e de sua correlação com a atividade catalítica. Os compostos foram caracterizados através de diferentes técnicas espectroscópicas (UV/Vis, IR e EPR), além de propriedades magnéticas, condutimetria e análise elementar. Uma espécie mononuclear com ligantes quelantes simples também foi isolada. A atividade catalítica desses complexos frente à oxidação de substratos, como 2,6-di-terc-butilfenol e 3,4-di-hidroxifenilalanina (L-dopa), pelo oxigênio molecular foi então verificada, mostrando que em geral são bons miméticos das proteínas tirosinases, dependentes de cobre, apresentando atividades cresolase e catecolase. Os complexos com ligantes macrocíclicos mostraram-se mais eficientes como catalisadores do que os demais compostos dinucleares, cujos ligantes não eram macrocíclicos. A formação da respectiva quinona foi monitorada espectrofotometricamente e a lei de velocidade determinada exibiu uma dependência de pseudoprimeira ordem com relação à concentração do substrato e do complexo. Os resultados obtidos indicaram que as características estruturais destes complexos (natureza dos ligantes, fatores estéricos e aspectos geométricos) parecem ser determinantes de suas atividades como catalisadores de oxidação.New dinuclear copper(II) complexes involving hydroxylated diimine ligands, macrocyclic and macroacyclic, were prepared, with the aim of comparing their structural features. One mononuclear species with simple holder ligand was too isolated. Different techniques were used in characterization of these complexes: UV/Vis, IR and EPR spectroscopies, conductimetry, elemental analyses and magnetic proprieties). The catalytic activity these complexes towards of substrate oxidation, such as 2,6-di-tert-butylphenol e 3,4-di-hydroxyphenylalanina (L-Dopa), by molecular oxygen was verified, showing in general are goods as mimetics of the tyrosinases proteins, copper depends, presenting phenolase and catecholase activity. Complexes with macrocyclic ligands showed more efficient as catalysts than another dinuclear compounds, with macroacyclic ligands. The growth of correspondent quinone was spectrophotometrically monitored and the velocity law established show a pseudo-first order dependence in relation the substrate and complex concentration. The results obtained indicate that structural characteristics these complexes (kind of ligands, hindrance factor and geometric aspects) are determiner of the their activity as catalyst in oxidation reaction.
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Choi, Joonhyuk. "Sensing Inorganic Phosphate Starvation by the Phosphate-Responsive (PHO) Signaling Pathway of Saccharomyces cerevisiae." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10878.
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Inorganic phosphate \((P_i)\) is an essential nutrient whose intracellular levels are maintained by the PHO pathway in Saccharomyces cerevisiae. \(P_i\) limitation triggers upregulation of the PHO genes whose gene products primarily function to counterbalance the \(P_i\) deficiency. Despite a growing catalogue of genes that are involved in signaling of the PHO pathway, little is known about how cells actually sense \(P_i\) limitation. To better characterize the \(P_i\) sensing mechanism, I exploited two comprehensive and orthogonal approaches: 1) genome-wide genetic screening to identify novel genes involved in signaling \(P_i\) limitation through the PHO pathway and characterization of genetic interactions among these genes and 2) liquid chromatography /mass spectrometry (LC/MS)-based metabolic profiling to characterize the metabolomic response to changes in \(P_i\) availability. In genome-wide screening, I found that the aah1 mutant constitutively activated the PHO pathway and showed that AAH1 is involved in regulating PHO pathway activity. Moreover, I identified several novel genetic interactions of genes involved in inositol polyphosphate metabolism with those involved in purine metabolism and mitochondrial fatty acid biosynthesis.Through metabolomic profiling, I showed that all adenine nucleotides were downregulated in the constitutively induced ado1, adk1, and aah1 mutants in high \(P_i\) as well as in the wild type strain in low \(P_i\). These observations led to the hypothesis that downregulation of adenine nucleotides triggers activation of the PHO pathway. However, I find that decreases in adenine nucleotides appear to be the consequence of downregulation of glycolysis and of the pentose phosphate pathway rather than an activation signal for the PHO pathway.Among all the detected metabolites, S-adenosyl-L-homocysteine (SAH) responded the most quickly and significantly to changes in \(P_i\) concentration. It was known that SAH is an inhibitor of de novo synthesis of phosphatidylcholine (PC). I showed that overall PC levels were downregulated in low \(P_i\), suggesting that phospholipid metabolism is downregulated in low \(P_i\) conditions. Furthermore, I observed that exogenous SAH induces activation of the PHO pathway in high \(P_i\) implying a possible role of SAH as an initiating activation signal of the PHO pathway.Chemistry and Chemical Biology
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Tang, Christian C. "Structure and Activity of Metallo-Peptides." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6961.
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Metal ions are ubiquitously found in all living systems and play vital roles in supporting life forms by performing an array of biological activities. Such biological activities include binding and transforming organic molecules, and also acting as active centers and cofactors for catalysis of various acid-base and redox reactions in biological system. The main focus in bioinorganic chemistry is to elucidate the structural and functional roles of metals in biological systems. Among all transition metal ions, Cu2+ and Fe3+ are especially versatile and important due to their abilities to go through redox efficiently.
This dissertation can be divided into four main chapters. The bioinorganic chemistry of Cu- and Fe-containing proteins were briefly discussed in Chapter one. The next chapter focuses on bacitracin, a cyclic peptide-based antibiotic produced by soil bacteria Bacillus subtilis. Bacitracin is a metalloantibiotics that can coordinate with many transition metal ions and exhibit different biological activities. In the first part of Chapter two, the aim is to explore the chemicals interactions in soil micro-ecology by investigating the interactions of different flavonoids and Cu(II)-bacitracin complex. The second part of chapter two demonstrated the binding and oxidation activity of iron(III)-bacitracin. Metal-mediated oxidative stress plays a crucial role in the development of different neurodegenerative diseases. In chapter 3, various synthetic and natural compounds were used to inhibit the oxidation chemistry mediated by Cu(II)-beta-amyloid complex associated with Alzheimer’s disease. Many proteins incorporate copper ions at their active sites for different functions, and among all of the chemistry copper-containing-proteins can perform, one of the most interesting aspect is the ability to bind and activate O2. Therefore, the biomimetic of two different Cu(II) complexes were investigated. In all studies, a combination of kinetic and different spectroscopic methods (UV-vis, NMR and resonance Raman spectroscopy) were used to study their metal binding and activity.
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Gallo, Annastassia Dawn. "Homeostasis and trafficking of hydrolysis-prone metals in cells, proteins, and small molecules." Diss., Temple University Libraries, 2019. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/568230.
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ChemistryPh.D.
Nature uses inorganic elements for biological processes based on the useful chemistry, abundance, and availability of each metal. Transition metals are critical in the biogeochemical cycling of essential elements and the bioinorganic chemistry of organisms. Hydrolysis-prone metals such as iron and titanium are abundant on Earth but are mostly insoluble in oxic aqueous environments. Nearly every organism requires iron for survival, therefore Nature evolved to stabilize iron from hydrolysis and hydrolytic precipitation through protein and small molecule mechanisms. Like iron, titanium primarily exists as insoluble mineral oxides and is second only to iron as the most abundant transition metal in the Earth’s crust. Despite the reputation as an inert and insoluble metal, titanium can be solubilized and made bioavailable through by chemical and biological weathering. Currently there is no known native role for titanium, however it is quite bioactive. As a stronger Lewis acid, titanium can compete with iron in binding to biomolecules and proteins. It is of interest to investigate the interactions between hydrolysis-prone metals and biological systems, from whole cell organisms to proteins and small molecules. The non-pathogenic bacterium Rhodococcus ruber GIN-1 was isolated for its ability to strongly adhere to titanium dioxide (TiO2) over other metal oxides, providing an opportunity to study the interactions between whole bacterial cells and metal oxides. The GIN-1 strain incorporates Ti(IV) ions into its biomass after adherence to anatase, rutile, and a mixture of the two morphologies. Six metals were quantitated in TiO2-exposed and control (unexposed) cells by inductively coupled plasma optical emission spectroscopy. The exposure to TiO2 caused a significant uptake of titanium with concomitant loss of iron, zinc, and possibly manganese. A collaborative project with the Strongin laboratory at Temple University works to develop stable, biomaterial photocatalysts for environment remediation of toxic inorganic contaminants. Ferritins are a class of proteins that mineralizes and stores iron as a non- toxic ferrihydrite nanoparticle. These proteins can be photoactivated with ultraviolet light to release iron from its core to remediate environmental contaminants. Ferritin can be sensitized with plasmonic gold nanoparticles to extend the photoactivity of the catalyst to the visible spectrum. Work in this thesis highlights the contribution to this collaboration from the Valentine laboratory, included the expression and purification of proteins in E. coli (human H-chain ferritin, human L-chain ferritin, and bacterial DNA protection from starved cells protein), mutation of proteins to improve sensitization of catalyst, and biomineralization with iron and titanium. The trafficking of hydrolysis prone metals is vital for the survival of nearly every organism. Iron transport proteins such as transferrins are studied to understand how nature utilizes a difficult essential metal across the domains of life. Most transferrins have two homologous lobes and are believed to have evolved from a gene duplication of a monolobal transferrin. The ascidian Ciona intestinalis has genes for both a bilobal and monolobal transferrin. Nicatransferrin (nicaTf), the monolobal transferrin from C. intestinalis, is a primitive protein that may provide insight on the evolution of transferrins in higher organisms. It is advantageous to use E. coli expression systems to produce recombinant proteins, however protein misfolding and aggregation can be a concern. To improve expression of nicaTf in E. coli, codon optimization and disulfide bonded protein expression were used. Finally, siderophores are small, high affinity iron-chelating molecules secreted from lower organisms that scavenge iron in iron-limiting conditions. R. ruber GIN-1 and R. ruber DSM 43338 strains both secrete siderophores in artificial seawater media. There are several siderophores identified from Rhodococcus species, however none have been reported from any R. ruber strain. A new siderophore was isolated and preliminary work has been done to purify and characterize the molecule. Understanding the siderophore- metal ion interactions may help elucidate the mechanism of how R. ruber cells obtain titanium from the metal-oxide particles.
Temple University--Theses
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Abbey, Eric Ryan 1980. "Boron in Disguise: Towards BN Biomimics." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11979.
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xv, 219 p. : ill. (some col.)Chemists have long recognized the potential of the BN bond to mimic CC double bonds in aromatic systems. Phenyl and indole are two of the most important arenes in natural systems, as well as medicine, applied chemistry, and materials science. Despite the potential of BN arenes as phenyl and indole mimics in biomolecules, few isoelectronic and isostructural BN biomolecules have been synthesized. Substitution of BN for C=C imparts tunability to aromatic systems, giving new and potentially valuable properties to the resulting molecules. Our group has sought to expand the utility of BN arenes by developing the synthetic arsenal available to chemists seeking to incorporate the BN bond into biological and other organic molecules of importance. The scope of this dissertation is twofold: (1) development of the first "fused" BN indole, including a survey of its reactivity towards electrophiles, synthesis of the parent N -H compound with complete characterization, and a comparison to natural indole and (2) expansion of the synthetic methodologies for constructing 1,2-dihydro-1,2-azaborine derivatives, including complete structural characterization of a family of "pre-aromatic" and aromatic compounds and a protection-free synthesis of azaborines. The contributions outlined in this dissertation expand both the fundamental understanding of BN isosterism in aromatic molecules and the synthetic toolbox for chemists seeking to incorporate BN arenes into biological and other organic motifs. This dissertation includes previously published and unpublished coauthored material.
Committee in charge: Professor Kenneth M. Doxsee, Chair; Professor Shih-Yuan Liu, Advisor; Professor Victoria J. DeRose, Member; Professor Michael M. Haley, Member; Professor Janis Weeks, Outside Member
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Butler, Steven Kyle. "An Introductory Study of Solid Materials for Capture and Catalysis of Waste Stream Chemicals." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6845.
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Heterogeneous catalysts are key materials in research and industry. Herein we study two materials in different stages of development toward being applied as heterogeneous catalysts. First, MoO3SnO2 was synthesized and studied as a catalytic system similar to Sn-beta zeolites. While the Mo-based catalyst did not show similar activity to Sn-beta, it did show interesting reactivity in activating carbonyls and oxidizing organic substrates. Second, a method was developed for grafting amines onto carboxylic acid functionalized carbon nanotubes for CO2 capture. The method was successful for grafting monomer ethylamine groups onto CNT and can be further developed to allow for polymeric amine groups to be grafted.
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Österlund, Lise-Lotte. "Redox models in chemistry : A depiction of the conceptions held by secondary school students of redox reactions." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-35770.
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According to previous research, students show difficulties in learning redox reactions. By the historical development different redox models exist to explain redox reactions, the oxygen model, the hydrogen model, the electron model and the oxidation number model. This thesis reports about three studies concerning conceptions held by secondary school students of redox reactions. A textbook analysis is also included in the thesis. The first study was an investigation of the students’ use of redox models in inorganic contexts, their use of the activity series of metals, and the students’ ability to transfer redox knowledge. Then the students’ work with an open-ended biochemical task, where the students had access of the textbook was studied. The students talk about redox reactions, the questions raised by the students, what resources used to answer the questions and what kind of talk developed were investigated. A textbook analysis based on chemistry books from Sweden and one book from England was performed. The redox models used as well as the dealing with redox related learning difficulties was studied. Finally, the students’ conceptions about redox in inorganic, organic and biochemistry after completed chemistry courses were studied. The results show that the students were able to use the electron model as a tool to explain inorganic redox reactions and the mutuality of oxidation and reduction was fundamental. The activity series of metals became a tool for the prediction of reducing agent in some reactions. Most of the students rejected that oxygen is a prerequisite for a redox reaction. In the biochemical task the resource most used to answer the raised questions were the students’ consultation of the textbook – together or individually. Most questions resulted in short answers and the majority of these questions were answered. Questions concerning redox were analysed by the students and integrated into a chemical context but they could neither identify the substances oxidised or reduced nor couple the concepts to transfer of hydrogen atoms. The majority of these redox questions became unanswered. The textbook helped the students to structure a poster as well as to answer basic chemistry questions. For questions about organic and biochemical redox, the book was of no help. The textbook analysis showed that all historical redox models are used. Different models are used in inorganic, organic and biochemistry. The mutuality of oxidation and reduction is treated differently in subject areas. The textbooks did not help the reader linking the different redox models that were used. Few redox-related learning difficulties are addressed in the books. After completed chemistry courses the students had major problems to justify a redox reaction explained by transfer of hydrogen atoms both in the organic and biochemistry examples.
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Luo, WeiLong. "Synthetic Investigation on the Biomimetic Metal-Catalyzed Sulfoxidations and Photochemical Generation of a Highly Reactive Ruthenium(V)-Oxo Porphyrin." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1636.
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Catalytic oxidation plays a crucial role in current chemical and pharmaceutical industries which is also a leading technology for green chemical processes. In Nature, the ubiquitous cytochrome P450 enzymes can catalyze a wide variety of oxidation reactions with high efficiency and selectivity. Many transition metal catalysts are designed as the biomimetic model of cytochrome P450 enzymes. In this work, series of metalloporphyrins and metallocorroles have been successfully synthesized to investigate and develop catalytic selective oxidation of sulfides to sulfoxides.
Manganese(III) porphyrin complexes (2) and manganese(III) corrole complexes (6) with iodobenzene diacetate [PhI(OAc)2] as a mild oxygen source exhibited remarkable catalytic activity toward selective oxidation of sulfides to sulfoxides under mild conditions. Conspicuous is the fact that readily soluble PhI(OAc)2 in the presence of a small amount of water is more efficient than the commonly used PhIO and other oxygen sources under identical conditions. It was found that the reactivity of manganese(III) porphyrin catalysts was greatly affected by axial ligand and the weakly binding chlorate gave the highest catalytic activity in the oxidation of sulfide. Both porphyrin-manganese and corrole-manganese catalysts catalyzed the highly selective oxidation of para-substituted thioanisoles with PhI(OAc)2 in the presence of a small amount of water. Complete conversion and of sulfide and excellent selectivities for sulfoxide were achieved within 120 min.
We discovered that photo-disproportionation of a bis-porphyrin-diruthenium(IV)- μ-oxo dimer gave a porphyrin-ruthenium(III) species and a putative poprhyrinruthenium( V)-oxo species that can be detected and studied in real time using laser flash photolysis methods. As determined by its spectral and kinetic behavior, the same oxo transient was also formed by photolysis of a porphyrin-ruthenium(III) N-oxide adduct. Second-order rate constants for reactions with several substrates at 22 °C were determined; representative values of rate constants were kox = 6.6 × 103 M-1 s-1 for diphenylmethanol, kox = 2.5 × 103 M-1 s-1 for styrene, and kox = 1.8 × 103 M-1 s-1 for cyclohexene.
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Wang, Vincent Cho-Chien. "New insights into enzymatic CO₂ reduction using protein film electrochemistry." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:f1061854-f6b8-4562-81e0-968c80e1da3a.
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Carbon monoxide dehydrogenase (CODH) is known to catalyze CO oxidation and CO₂ reduction reversibly with the minimal overpotential. A great advantage of protein film electrochemistry (PFE) is its ability to probe catalysis over a wide range of potentials, especially in the low potential region required for CO₂ reduction. CODH I and CODH II from Carboxydothermus hydrogenoformans(Ch) and the composite enzyme acetyl-CoA synthase/carbon monoxide dehydrogenase (ACS/CODH) from Moorella thermoacetica(Mt) are intensively studied throughout this thesis. The different catalytic redox-states in CODH, Cox (inactive state), Cred1 (for CO oxidation) and Cred2 (for CO₂ reduction) as characterized by spectroscopy, are studied by PFE in the presence of substrate-mimic inhibitors. Cyanide, isoelectronic with CO, mainly inhibits CO oxidation, whereas cyanate, isoelectronic with CO₂, mainly targets CO₂ reduction. Sulfide inhibits CODH rapidly when the potential is more positive than −50 mV, which suggests that sulfide reacts to form a state at the oxidation level of Cox in CODH and is not an activator for CODH catalysis as suggested before. Thiocyanate only partially inhibits CO oxidation. No inhibition of CODH by azide is detected, which is in contrast with previous studies with ACS/CODHMt. The main differences between CODH ICh and CODH IICh are the stronger CO product inhibition and inhibition of CODH IICh by cyanide. These discoveries might shed light on the possible role of CODH IICh,/sub> in biological systems. In comparison with bidirectional (reversible) electrocatalysis by CODH ICh and CODH IICh, only unidirectional electrocatalysis for CO oxidation by ACS/CODHMt is observed with an overpotential of 0.1 V and the electrocatalytic current is much smaller. In order to identify whether ACS influences the performance of CODH, several chemical reagents, such as sodium dodecyl sulfate (which separates CODH and ACS partially), 1, 10-phenanthroline, (which inhibits the active site in ACS) and acetyl-CoA (the product of the reaction carried out by ACS/CODHMt) are added. However, we have yet to observe any electrocatalytic current from CO₂ reduction. Inhibition of ACS/CODHMt by cyanide, cyanate and azide is consistent with previous studies by spectroscopy. Oxygen attack toward the active site in CODH is proved by cyanide protection. The inactive state, Cox can prevent oxygen attack and reductive reactivation restores CODH activity. In contrast, oxygen damages the active site irreversibly when CODH is in the Cred1 state. The new substrate, nitrous oxide (N₂O), isoelectronic with CO₂, is reduced by CODH and acts as the suicide substrate. Finally, hydrogen formation in the direction of CO oxidation and formate formation in the direction of CO₂ reduction by CODH are detected. The small solvent kinetic isotope effect is observed in CO oxidation. These findings suggest metal-hydride should play a role in CODH catalysis, which might provide a new direction to design better catalysts for CO₂ reduction.
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Stilgenbauer, Morgan Grasselli. "Development of New Platinum-Based Anticancer Agents Targeting Ovarian Cancer Stem Cells." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1595328319619319.
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Bradford, Seth Stephen. "The Design and Evaluation of Catalytic MetalloDrugs Targeting HCV IRES RNA: Demonstration of a New Therapeutic Approach." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345132549.
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Puckett, Nathan. "Effects of Binding Affinity between Bovine Serum Albumin and Platinum Drugs." TopSCHOLAR®, 2017. http://digitalcommons.wku.edu/theses/1977.
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Platinum complex drugs such as cisplatin have been used as highly successful chemotherapy drugs since the 1970s. We are interested in how the ligands attached to cisplatin analogs influences their reactivity with biologically relevant targets along with time and amount. For this study, reactions were conducted to determine the reactivity between different platinum compounds and the protein bovine serum albumin. Various platinum compounds with different ligands were reacted in varying amounts with albumin in ammonium acetate buffer for either 1 hour, 4 hours, or 24 hours. Each reaction was quenched after the designated reaction time by dialysis and the platinum bound to the protein was determined by use of ICP. LC-MS was used to find exact peptide residues platinum complexes prefer to bind with but was found to be ineffective. Results show that time has a more significant affect on binding over amount of platinum present. In respect to changing the leaving or carrier ligands on the platinum complex, these changes on the complex did not affect binding significantly with bovine serum albumin. Triamine platinum complexes also seem to bind significantly more than diamine platinum complexes along with anionic form platinum complexes binding significantly better than the cationic form platinum complexes.
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Miles, Meredith. "The Great Potential of Redox Active Ligands: Applications in Cancer Research and Redox Active Catalysis." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1546621531283595.
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Chen, Yao. "Synthesis, Characterization and Mechanistic Studies of Biomolecules@mesoMOFs." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5199.
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Encapsulation of biomolecules is of great interest to research advances related to biology, physiology, immunology, and biochemistry, as well as industrial and biomedical applications such as drug delivery, biocatalysis, biofuel, food and cosmetics. Encapsulation provides functional characteristics that are not fulfilled by free biomolecules and stabilizes the fragile biomolecules. In terms of biocatalysis, solid support can often enhance the stability of enzymes, as well as facilitate separation and recovery for reuse while maintaining activity and selectivity. Various kinds of materials have been used for encapsulation of biomolecules, among which, porous materials are an important group. Metal-organic frameworks (MOFs) have attracted much attention and emerged as a new generation of highly porous functional materials with potential in a variety of fields such as gas separation and storage, catalysis, sensors and biomedical applications. Their structural versatility and amenability to be designed with specific functionality, together with their extra-large surface areas confer them a special place amongst traditional porous materials. In particular, because ligands can be designed with particular organic functional groups for specific interactions with biomolecules, they are attractive in the stabilization and retention of enzyme/proteins for biomedical or biocatalysis applications. With enlarged pore sizes, mesoporous (pore sizes in the range of 2 to 50 nm) MOFs are of great interest in the encapsulation of proteins. In this dissertation, I am focusing on the encapsulation of biomolecules into mesoporous MOFs (mesoMOFs) to estabilish the biomolecules@mesoMOF platform, including synthesis, characterization and mechanistic studies of a series of novel biomolecules@mesoMOF materials, and to develop the biomolecule@mesoMOFs platform for various applications.
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Abeyawardhane, Dinendra L. "Biometal-Induced Structural Consequences of α-Synuclein – the Parkinson’s Disease Protein." VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/5909.
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The pre-synaptic protein α-Synuclein (αS) is often linked to the pathology of Parkinson’s disease (PD), an age-related neurodegenerative disorder. Lewy bodies, the cytopathological hallmarks of PD, are found to be rich in aggregates of misfolded αS protein. Metal dyshomeostasis has also been linked to PD due to the accumulation of iron in the substantia nigra pars compacta, and diminished copper levels reported in this same region. Metal dyshomeostasis in the brain coupled with oxidative stress can enhance the aggregation of αS. Recently, it was confirmed that mammalian αS is universally acetylated at the N-terminus, a common post-translational modification in humans. The consequences of this modification have been understudied, and it is believed to impart a functional role under physiological conditions with respect to membrane-interactions and protein folding. In an attempt to elucidate the pathological mechanism behind PD with respect to the structural dynamics of the protein, our investigations were focused on physiologically prevalent, N-terminally acetylated αS (NAcαS) and its interaction with the most prevalent redox-active metal ions in the brain (iron and copper) under both aerobic and/or anaerobic conditions.
The structural features associated with metal-bound NAcαS differed depending on the iron oxidation states, where under aerobic conditions Feᴵᴵ stabilized an oligomer-locked, anti-parallel right-twisted β-sheet conformation that could potentially impart toxicity to neurons. In contrast, Feᴵᴵᴵ promoted a fibrillar structure rich in parallel β-sheets. N-terminal capping also altered the Cuᴵᴵ coordination sphere and had a dramatic effect on protein aggregation. Parallel studies on NAcαS variants with different site mutations near the putative copper binding sites (ex: H50Q and F4W) indicated that preferential binding shifts upon changes in the side chain residues. In depth analysis of the electron structure of Cuᴵᴵ-bound NAcαS using electron paramagnetic resonance spectroscopy (EPR) revealed a coordination sphere of N3O1 that includes the H50 residue in the wild-type protein that shifts to an O4 coordination sphere at the C-terminus upon Cuᴵᴵ binding to the disease-relevant H50Q variant. Immunoblotting analyses revealed that copper-induced redox chemistry promoted O2-activation and the subsequent formation of dityrosine crosslinks, a post-translational modification identified as a biomarker of PD. EPR-detection of tyrosyl radical formation in the presence of Cuᴵ-bound NAcαS further supported this radical coupling mechanism. Intermolecular crosslinks within the fibrillar core of NAcαS as well as intramolecular crosslinks within the C-terminal region underpin the role of metal-dioxygen chemistry in PD-related pathology.
The unique structural features resulting from iron vs copper coordination to NAcαS inspired studies directed at the synergistic effect of each individual metal species as revealed by photo-initiated crosslinking of NAcαS. C-terminal intramolecular tyrosine interactions were mainly impacted by the presence of both metals, which each have binding sites around the same region. These findings emphasize that protein dynamics, metal binding site conformational changes, as well as aggregation pathways can deviate drastically upon N-terminal acetylation of αS and that protein-metal interactions may play a vital role in PD etiology.
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Negrón, Ana Cecilia Valderrama. "Síntese e caracterização de carboxilatos de Rh(II) e seus adutos com metronidazol: ensaios biológicos com vistas à vtividade radiossensibilizadora de tumores." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/46/46134/tde-01092014-164032/.
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Radiossensibilizadores são definidos como agentes químicos que aumentam a sensibilidade das células hipóxicas à radiação, visando o aumento da eficácia da radioterapia no tratamento do câncer. Alguns Carboxilatos de Rh (II) e compostos nitroimidazólicos têm sido testados como radiossensibilizadores em doses elevadas de radiação, obtendo-se resultados significativos. Neste trabalho, foram sintetizados vários carboxilatos e um amidato de Rh (II): propionato, butirato, trifluoroacetato, citrato e trifluoroacetamidato, assim como os seus respectivos adutos com metronidazol, de fórmula geral: [Rh2(RCOO)4metro2] (R = CH3, C2H5, C3H7, C5 H7O5, e CF3) para o caso dos carboxilatos e [Rh2(CF3CONH) 4 metro2] para o aduto de trifluoroacetamidato. Os compostos foram caracterizados por análise elementar, espectroscopia eletrônica, infravermelho e de ressonância magnética nuclear de próton. O resultado desta caracterização permitiu estabelecer as rotas de síntese confirmando a formação dos carboxilatos tipo ponte e a presença do metronidazol nas posições axiais, numa relação 1:2. O efeito radiossensibilizador desses complexos de Rh (II) foi testado in vitro, irradiando-se, em atmosfera hipóxica, células de ovário de hamster chinês (CHO k1), na presença dos complexos, utilizando-se raios gama provenientes de uma fonte de 60Co, com doses de 2,7 e 4,3 Gy. Foi realizado teste de citotoxicidade para determinar as concentrações atóxicas de cada composto, eliminando a possibilidade de morte celular devido ao efeito tóxico dos mesmos. Na dose 2,7 Gy não houve nenhum efeito interessante; já com a dose de 4,3 Gy o [Rh2(CH3 COO)4] mostrou uma atividade radiossensibilizadora maior do que nos demais complexos. Os resultados foram semelhantes aos obtidos na literatura com doses de radiação até 10 vezes maiores. Devido à ausência de mudanças significativas no efeito radiossensibilizador entre os carboxilatos e amidato e seus respectivos adutos com metronidazol, foi determinada a constante de formação destes últimos, demonstrando que os mesmos sofrem decomposição quando em solução aquosa diluída.Radiosensitizers are chemical agents that enhance the radiation sensitivity of hipoxic tumor cells aiming to better radiotherapy efficacy in the treatment of cancer. Some Rhodium (II) carboxylates and its adducts with nitroimidazole derivatives, have been tested as radiosensitizers in high doses of radiation, being obtained significant results. In this work, several Rhodium carboxylates and one Rhodium amidate previously described were synthesized: propionate, trifluoroacetate, citrate and , trifluoroacetamidate, as well as their respective adducts with nitroimidazole of general formula [Rh2(RCOO)4metro2] for the carboxylates and [Rh2(CF3CONH)4metro2] for the trifluoroacetamidate adduct. The compositions where characterized by elementary analysis, electronic and infrared spectroscopy and proton nuclear magnetic resonance. The results of that characterization allowed us to establish the synthesis routes and confirm the bridge type structure of the Rodhium compounds, beyond the presence of the metronidazole at the axial positions in the proportions of 1:2. The radiosensitizing effects of these Rh (II) complexes were tested in vitro by irradiation of Chinese hamster (CHO k1) cells under hipoxic atmosphere in the presence of the complexes, using gamma rays from a 60Co source and doses of 2,7 and 4,3 Gy. A cytotoxicity test has been performed to determinate the non-toxic concentrations of these compounds, in order to rule out the possibility of cellular death induced by the complexe´s cytotoxicity. A 2,7 Gy dose showed no interesting effects but under a 4,3 Gy dose, the complex Rh2(CH3 COO)4 showed a higher radiosensitizing effect than the order compounds and close to previously reported effects which required high radiation doses. As there was not a significant change in the radiosensitizing effect between the carboxylate and the amidate and their respective metronidazole adducts it was performed the measurement of the formation constant of that adducts. The results of that measurements gave evidence of adduct decomposition when in dilute aqueous solution.
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Grabarczyk, Daniel Ben. "Molecular characterisation of bacterial proteins that interact with sulfur or nitrogen compounds." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b6b3e3fd-620f-467d-b063-01311fa7a9a2.
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Many bacteria use inorganic nitrogen and sulfur compounds for energy metabolism. These compounds are often toxic and so bacteria must adapt to survive their deleterious effects. Bacteria use specific proteins in order to metabolise, sense and detoxify these compounds. In this thesis protein interactions with inorganic nitrogen and sulfur compounds are examined at the mechanistic level. Intermediates in the Sox sulfur oxidation pathway are covalently attached to a cysteine on the swinging arm of the substrate carrier protein SoxYZ. An interaction between the Sox pathway enzyme SoxB and the carrier protein SoxYZ is demonstrated. A crystal structure of a trapped SoxB-SoxYZ complex at 3.3 Å resolution identifies two sites of interaction, one between the SoxYZ carrier arm and the SoxB active site channel and the other at a patch distal to the active site. The presence of a distal interaction site suggests a mechanism for promiscuous specificity in the protein-protein interactions of the Sox pathway. Using biophysical methods it is shown that SoxB distinguishes between the substrate and product forms of the carrier protein through differences in interaction kinetics and that the carrier arm-bound substrate group is able to out-compete the adjacent C-terminal carboxylate for binding to the SoxB active site. The thiosulfate dehydrogenase TsdA has an unusual His/Cys coordinated heme. TsdA catalyses oxidative conjugation of two thiosulfate molecules to form tetrathionate. Mass spectrometry and UV/visible spectroscopy are used to identify an S-thiosulfonate reaction intermediate which is covalently attached to the cysteine heme ligand. A catalytic mechanism for TsdA is proposed using a crystal structure of TsdA at 1.3 Å resolution alongside site-directed mutagenesis of active site residues. Nitric oxide is produced by the mammalian immune response to kill bacterial pathogens. Part of the killing mechanism occurs through the reaction of nitric oxide with protein-bound iron-sulfur clusters. However, the same type of reaction is also exploited by nitric oxide-sensing bacterial proteins. An infrared spectroscopy approach is developed to detect the products of iron-sulfur protein nitrosylation. Using this methodology it is shown that the presence of trace O2 strongly impacts which products are formed in these nitrosylation reactions. These observations are of physiological relevance because bacteria are often exposed to NO under aerobic conditions during an immune response.
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Hunt, Andrew P. "Kinetic and Mechanistic Studies on the Reaction of the Reduced Vitamin B12 Complex Cob(II)alamin with Hydrogen Peroxide." Kent State University Honors College / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ksuhonors1367864401.
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Kwong, Ka Wai. "Visible-Light Generation of High-Valent Metal-Oxo Intermediates and a Biomimetic Oxidation Catalyzed By Manganese Porphyrins with Iodobenzene Diacetate." TopSCHOLAR®, 2016. http://digitalcommons.wku.edu/theses/1743.
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High-valent iron-oxo intermediates play central roles as active oxidants in enzymatic and synthetic catalytic oxidations. Many transition metal catalysts are designed for biomimetic studies of the predominant oxidation catalysts in Nature, the cytochrome P450 enzymes.
In this work, a new photochemical method to generate high-valent iron-oxo porphyrin models was discovered. As controlled by the electronic nature of porphyrin ligands, iron(IV)-oxo porphyrin radical cations (Compound I model) and iron(IV)-oxo porphyrin derivatives (Compound II model) were produced. These observations indicate that the photochemical reactions involve a heterolytic cleavage of O-Br in precursors to give a putative iron(V)-oxo intermediate, which might relax to Compound I through electron transfer from porphyrin to the iron or undergo rapid comproportionation reaction with residual iron(III) to afford the Compound II derivative.
Furthermore, visible light photolysis of bis-porphyrins-dimanganese(III)-μ-oxo complexes, [MnIII(Por)]2O, was studied in three porphyrin systems. Direct conversion of manganese(III)-μ-oxo dimers to manganese(IV)-oxo porphyrins [MnIV(Por)(O)] and manganese(III) products was observed in benzene solution upon light irradiation. The spectral signature of [MnIV(Por)(O)] was further confirmed by production of the same species in the reported reaction of the [MnIII(Por)Cl] with PhI(OAc)2. Continuous irradiation of bis-porphyrins-dimanganese(III)-μ-oxo complexes in the presence of pyridine or triphenylphospine gave rise to the formation of [MnII(Por)(Py)] or [MnII(Por)(PPh3)], which are stable to be detected. A photo-disproportionation mechanism similar to that for bis-porphyrins-diiron(III)-μ-oxo complex was proposed to explain above photochemical behaviors of bis-porphyrins-dimanganese(III)-μ-oxo complexes.
With iodobenzene diacetate [PhI(OAc)2] as the oxygen source, manganese(III) porphyrin complexes exhibit remarkable catalytic activity towards the selective oxidation of alkenes and activated hydrocarbons. Conspicuous is the fact that the readily soluble PhI(OAc)2 in the presence of a small amount of water is more efficient oxygen source than the commonly used PhIO under same conditions. High selectivity for epoxides and excellent catalytic efficiency with up to 10,000 Turnovers (TONs) were achieved in alkene epoxidations. A manganese(IV)-oxo porphyrin was observed in the oxidation of the manganese(III) porphyrin and PhI(OAc)2. However, catalytic competition and Hammett studies suggested that the more reactive manganese(V)-oxo intermediate was favored as the premier active oxidant, even it is too short-lived to be detected in the catalytic reaction.
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Deblock, Michael C. "The Synthesis, In Vitro and In Vivo Testing of Silver N-Heterocyclic Carbenes and Imidazolium Complexes." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1353951003.
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Pryor, Donald Edward. "Synthesis and Bioactivity Studies of Nanoparticles Based on Simple Inorganic and Coordination Gallium Compounds as Cellular Delivering Vehicles of Ga(III) Ions for Potential Therapeutic Applications." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1543554532063877.
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Chitranshi, Priyanka. "Interactions of small molecules with duplex DNA and lesion containing G-quadruplex DNA." Scholarly Commons, 2013. https://scholarlycommons.pacific.edu/uop_etds/145.
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The low redox potential of guanines (G 1.29 V vs. NHE) compared to other nucleobases, makes them potentially susceptible to attack by exogenous and endogenous damaging species. This property of guanine has also been utilized for the development of several anticancer agents including the well-known platinum complexes, cisplatin and carboplatin. The two closely related nickel complexes, NiCR and NiCR-2H, exhibit significant differences in cytotoxicity towards MCF-7 cancer cells. In the first part of this work, we explain this difference using biochemical and biophysical approaches to study their interactions with duplex DNA. The nickel complexes were found to selectively oxidize guanines in bulged DNA structures in the presence of oxidant and notably NiCR-2H oxidizes guanines more efficiently than NiCR. According to 1 H NMR studies, NiCR-2H binds strongly to the N7 position of dGMP compared to NiCR and could be an important oxidation product of NiCR under physiological conditions. The second part of this work focuses on the secondary DNA structures known as G-quadruplex formed in the guanine rich telomeric region. G-quadruplex is formed by stacking of G-quartets (a coplanar cyclic array of four Gs) on top of each other. Its formation is known to inhibit the activity of the reverse transcriptase telomerase that is overexpressed in 80-90% cancer cells. The guanines in telomeric DNA are readily oxidized due to their low redox potential and the major oxidation product is 7, 8-dihydro-8-oxoguanine (OxodG). OxodG (0.58 V vs. NHE) can further be oxidized in the presence of one electron oxidants and the resulting product forms adducts with endogenous nucleophiles such as spermine. In light of these findings, we hereby designed and synthesized novel bifunctional perylene derivatives that can selectively bind to the telomeric DNA via G-quadruplex formation and subsequently react with OxodG in close proximity. These compounds have strong binding affinity towards G-quadruplex and can significantly stabilize the OxodG containing G-quadruplex motif by end stacking on the upper G-quartet. The effect of these compounds on telomerase activity and cytotoxicity towards Hep3B cancer cells was also evaluated.
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Alves, Wendel Andrade. "Espécies polinucleares de cobre e ferro com catalisadores de oxidação e modelos de sítios ativos." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/46/46134/tde-08072016-171620/.
Full textAbstract:
Diferentes complexos de cobre(II), contendo ligantes do tipo base de Schiff e um grupamento imidazólico, com interesse bioinorgânico, catalítico e como novos materiais, foram preparados na forma de sais perclorato, nitrato ou cloreto e caracterizados através de diferentes técnicas espectroscópicas (UV/Vis, IR, EPR, Raman) e espectrometria de massa Tandem (ESI-MS/MS), além de análise elementar, condutividade molar e medidas de propriedades magnéticas. Alguns destes compostos, obtidos como cristais adequados, tiveram suas estruturas determinadas por cristalografia de raios-X. As espécies di- e polinucleares contendo pontes cloreto, mostraram desdobramentos das hiperfinas nos espectros de EPR, relacionados à presença do equilíbrio com a respectiva espécie mononuclear, devido à labilidade dos íons cloretos, dependendo do contra-íon e do tipo de solvente utilizado. Adicionalmente, em solução alcalina, estes compostos estão em equilíbrio com as correspondentes espécies polinucleares, onde os centros de cobre estão ligados através de um ligante imidazolato. Em meio alcalino, estes compostos polinucleares contendo ponte imidazolato foram também isolados e caracterizados por diferentes técnicas espectroscópicas e magnéticas. Através da variação estrutural e também do ligante-ponte foi possível modular o fenômeno da interação magnética entre os íons de cobre em estruturas correlatas di- e polinucleares. Os respectivos parâmetros magnéticos foram obtidos com ajuste das curvas experimentais de XM vs T, correlacionando-se muito bem com a geometria, ângulos e distâncias de ligação entre os íons, quando comparado com outros complexos similares descritos na literatura. Posteriormente, estudaram-se os fatores relacionados com a reatividade de todas essas espécies como catalisadores na oxidação de substratos de interesse (fenóis e aminas), através da variação do tamanho da cavidade nas estruturas cíclicas ou de variações no ligante coordenado ao redor do íon metálico. Vários deles se mostraram bons miméticos de tirosinases e catecol oxidases. Um novo complexo-modelo da citocromo c oxidase (CcO), utilizando a protoporfirina IX condensada ao quelato N,N,-bis[2-(1,2-metilbenzimidazolil)etil]amino e ao resíduo de glicil-L-histidina, foi sintetizado e caracterizado através de diferentes técnicas espectroscópicas, especialmente EPR. A adição de H2O2 ao sistema completamente oxidado, FeIII/CuII, a -55°C, ou o borbulhamento de oxigênio molecular a uma solução do complexo na sua forma reduzida, FeII/CuI, saturada de CO, resultou na formação de adutos com O2, de baixo spin, estáveis a baixas temperaturas.Different Schiff base copper(II) complexes containing an imidazole ligand were prepared as perchlorate, nitrate and chloride salts, and characterized by different techniques (UV/Vis, IR, EPR, Raman) and tandem mass spectrometry (ESI-MS/MS), besides elemental analysis, conductivity measurements and magnetic properties. Some of these complexes, suitable crystals were isolated, allowing its structure to be determined by X-ray crystallography. Equilibria involving mono- and dinuclear species containing chloro-bridges were monitored in solution by EPR spectra, indicating a significant dependence on the solvent, and the counter-ion. In alkaline solution, deprotonation of the imidazole moiety promotes a self-assembled process, by coordination of the irnidazolate nitrogen atom to a copper(II) center of an adjacent unit, leading to the macrociclic or zig-zag-chain structures. These complexes were isolated and characterized by different spectroscopy techniques and magnetic susceptibility. The use of different bridging ligands and well-designed polydentate ligands afforded correlated structural features and exchange coupling constant in a series of di- e polinuclear copper(II) complexes. The magnetic parameters of these compounds were determined by temperaturedependent magnetic studies XM vs T, showing that the sign and the magnitude of the exchange coupling constant depends of the geometry, angle at the bridge, as well as on the bond length between paramagnetic ions, when compared with other complexes already described in the literature. The catalytic activity of the obtained complexes toward the usual biological oxidant, molecular oxygen, were then compared. Most of the di- and polynuclear compounds showed to be efficient catalysts of the aerobic oxidation of amines and o henolic substrates. Differinvg in some structural features, their tyrosinase-like catalytic activity was verified to be influenced by several factors, including steric hindrance of the ligands, cavity dimensions and accessibility of the oxidant to the catalytic center. A new biomimetic model system of the cytochrome c oxidase (CcO) derived from protohemin-IX and it contains a glycyl-L-histidine methyl ester arm axially binds the iron; the bis(benzimidazole) group acts as copper-coordinating site. has been prepared and characterized by different spectroscopic techniques, including EPR spectroscopy. The H2O2 addiction to the fully oxidised state of the system at -55ºC, or bubbling molecular oxygen into a CO-saturated solution of the reduced FeII/CuI state of the complex, resulted in a low spin oxygenated intermediate.
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Aitha, Mahesh Kumar. "SPECTROSCOPIC STUDIES ON ACTIVE METALLO-ß-LACTAMASES." Miami University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=miami1440671336.
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Bergstrom, Alexander R. "SPECTROSCOPIC AND MECHANISTIC STUDIES OF METALLO-BETA-LACTAMASE INHIBITORS AND THE STRUCTURE-FUNCTION RELATIONSHIP OF NEW DELHI METALLO-BETA-LACTAMASE VARIANTS." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1524154064246174.
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Deb, Tapash K. "Bioinspired Redox Active Pseudotetrahedral Ni(II) Thiolate and Phenolate Complexes: Synthesis, Characterization, Alkylation Kinetics and Molecular Oxygen Activation." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1377256181.
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Radabaugh, Timothy. "Oxidation and reduction of inorganic arsenic in mammalian systems." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280379.
Full textAbstract:
Arsenic is a toxic metalloid and is ubiquitous in our environment. In ancient cultures it was valued as a poison and today is becoming an increasing public health problem. Chronic arsenic exposure has a broad range of toxic effects including cancer. Currently millions of people are exposed to higher levels of arsenic in their food and drinking water than is considered safe by the World Health Organization. Although arsenic metabolism is not completely understood, it is known that inorganic arsenate is reduced to arsenite which can then be methylated and excreted in the urine. It is also known that some arsenic is retained in the body, presumably by binding to cellular proteins. To better understand how arsenic is metabolized, our approach was to identify and characterize proteins that are involved in arsenic metabolism. Using biochemical approaches we demonstrated that arsenate reductase activity from human liver was purine nucleoside phosphorylase (PNP). We were able to demonstrate that calf spleen PNP has arsenate reductase activity in vitro in the presence of inosine and dihydrolipoic acid, and that the reaction exhibits Michaelis-Menten kinetics. This identifies an enzymatic route for arsenate reduction. We also demonstrate that ferritin, an iron storage protein containing phosphate, can bind arsenic both in vitro and in vivo. In addition, we demonstrate that ferritin can oxidize arsenite to arsenate, and then interact with arsenate as it does with phosphate. We also establish that arsenate can inhibit ferritin's ability to store iron in vitro. Our results combined with data reported by others, suggest that DNA damage and enzyme inactivation associated with arsenic challenge may occur via reactive oxygen species generated by arsenic-iron redox reactions in ferritin, and that iron may augment arsenic toxicity. The interaction between ferritin and arsenate has two important implications. First, it suggests that iron exposure may be an important parameter to examine in epidemiological studies of arsenic sensitivity. Second, it suggests that iron chelation therapy might be beneficial in conjunction with arsenic chelation therapy for patients suffering from acute arsenic poisoning.
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Silveira, Vivian Chagas da. "Investigação da atividade biológica de complexos de cobre(II) com ligantes inspirados em biomoléculas." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/46/46134/tde-15062009-154840/.
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Neste trabalho, alguns novos complexos imínicos de cobre(II) com ligantes inspirados em biomoléculas como oxindóis, contendo grupos indólicos, imidazólicos ou pirrólicos com diferentes características estruturais, foram sintetizados e caracterizados por análise elementar, espectrometria ESI-MS e espectroscopias IV, UVNis e EPR. As possíveis interações desses complexos de cobre com a albumina humana (HSA) e com o plasma sanguíneo foram estudadas através das técnicas EPR, CD e SDS-PAGE, indicando que estas ocorrem principalmente no sítio N-terminal da proteína. Suas reatividades frente a compostos biológicos relevantes, tais como glutationa, ascorbato e peróxido de hidrogênio, também foram verificadas. Alguns dos complexos estudados podem ser ativados por glutationa, ascorbato ou peróxido de hidrogênio, sendo capazes de gerar espécies reativas de oxigênio em concentrações significativas, na presença desses redutores ou oxidantes biológicos. Adicionalmente, as propriedades pró-oxidantes de tais complexos foram investigadas, visando elucidar estudos prévios de suas atividades pró-apoptótica e antitumoral. Alguns destes complexos foram mais eficientes em causar danos oxidativos à 2-deoxi-D-ribose, enquanto outros foram mais eficientes em causar oxidantes na proteína HSA, com formação de grupos carbonílicos, principalmente em presença de H202. Experimentos de CD complementaram estes resultados, indicando que somente alguns complexos causaram modificações na α-hélice da proteína. Experimentos de EPR com captador de spin, na presença de HSA e H202, mostraram a formação de quantidades apreciáveis de radicais hidroxil e radicais de carbono, em presença de peróxido de hidrogênio. Além disso, os complexos apresentaram notável habilidade de ligação ao DNA e conseqüente atividade nuclease, promovendo clivagens nas duas fitas. Experimentos de fluorescência, EPR, gel de eletroforese marcado com α-32P-UTP e CD foram ainda realizados, visando elucidar o mecanismo de ação destes complexos no meio biológico. Estes experimentos indicaram que eles podem se associar ao DNA, através de suas bases ou pela interação com a deoxi-ribose, já que promoveram danos oxidativos nestes substratos. Entretanto, não catalisam a hidrólise dos grupos fosfato, atuando, portanto, predominantemente por um mecanismo oxidativo. Através de CD, poucas perturbações na elipsicidade do DNA foram observadas, o que indica que estes complexos provavelmente estão localizadas nas cavidades ou alças do ácido nucléico.Some novel imine-copper(II) complexes with ligands inspired in biomolecules such as oxindoles, containing indole, pirrole or imidazole moieties with different structural features were synthesized, and characterized by elemental analysis, IV, UV/Vis and EPR spectroscopies, and ESI-MS spectrommetry. Interactions of these complexes with human serum albumin (HSA) and human plasma were verified by EPR, CD and SDS-PAGE techniques, showing that they occur mainly at the N-terminal site of the protein. Their reactivity towards biological relevant compounds, such as glutathione, ascorbate and hydrogen peroxide were also verified; some of them are capable of generating ROS in significant concentrations, in the presence of these reducing or oxidant agents. Additionally, the activity of such copper(II) complexes in promoting oxidative damage to different substrates was investigated, in order to elucidate previous studies on their pro-apoptotic and antitumoral activity. Some of these complexes were much more efficient to cause oxidative damage to 2-deoxy-D-ribose, especially in the presence of hydrogen peroxide. On the contrary, others were more active in causing damage to HSA protein, with the formation of carbonyl groups. Experiments by CD corroborated these results, since only some of the complexes caused modifications in the protein -helix. EPR spin trapping experiments, in the presence of HSA and H2O2, showed significant generation of hydroxyl as well as carbon centered radicals. Moreover, all the complexes showed remarkable ability to bind to DNA, promoting double-strand cleavage, upon H2O2 activation. In order to investigate their mechanism of action, fluorescence, EPR, gel-electrophoresis with labeled α-32P-UTP and CD experiments were carried out. The results indicated that these complexes can bind to DNA through its bases or can interact with the deoxi-ribose rings, promoting oxidative damage to those substrates. On the contrary, they do not catalyze the hydrolysis of phosphate groups. By CD spectroscopy, little perturbations on the helicity conformation of the DNA were observed, indicating that these complexes are probably located in the grooves.
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Bludin, Alexey O. "Peptide-Porphyrin Self-Assembled Materials." Bowling Green State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1308097842.
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Balaratnam, Sumirtha. "BIOGENESIS AND FUNCTIONAL APPLICATIONS OF PIWI INTERACTING RNAs (piRNAs)." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1531753741509242.
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Roberts, Alexander Colin. "Production and Harvest of Microalgae in Wastewater Raceways with Resource Recycling." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1537.
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Microalgae can be grown on municipal wastewater media to both treat the wastewater and produce feedstock for algae biofuel production. However the reliability of treatment must be demonstrated, as well as high areal algae productivity on recycled wastewater media and efficient sedimentation harvesting. This processes was studied at pilot scale in the present research.
A pilot facility was operated with nine CO2-supplemented raceway ponds, each with a 33-m2 surface area and a 0.3-m depth, continuously from March 6, 2013 through September 24, 2014. The ponds were operated as three sets of triplicates with two sets continuously fed primary-clarified municipal wastewater at either a 2-day or 3-day hydraulic residence time (HRT), and one set fed the clarified effluent of the 3-day pond set. This second pond-in-series was operated with a 3-day HRT.
Areal biomass productivity is reported as gross and net, the former based only on biomass in the pond effluents and the latter subtracting the volatile suspended solids in the influent from those in the effluent. An estimate was also made of autotrophic biomass productivity, as differentiated from heterotrophic growth.
Over a year, net productivity averaged 83 metric tons per hectare per year (MT/ha-yr) for the 2-day HRT ponds, 52 MT/ha-yr for the 3-day HRT ponds, and 44 MT/ha-yr for the 3-day HRT ponds receiving clarified effluent of the first set of 3-day HRT ponds (i.e., recycled water). The lower net productivity of the pond receiving water recycling was attributed to two factors. First, the relatively high influent suspended solids concentrations were subtracted from the effluent suspended solids concentrations before net productivity was calculated. Second, the recycled water contained less soluble organic matter than the primary-clarified wastewater leading to less heterotrophic biomass production. The accumulation of inhibitory allelochemicals is a possible third cause of lower productivity
, but no specific information was collected on allelopathy.
Algae were harvested from pond effluent by sedimentation, with harvest efficiency most affected by the extent of natural bioflocculation occurring in the ponds. Some forms of bioflocculation are thought to be mediated by bacteria, which often make-up a substantial fraction of the settled flocs. Pond samples settled in 1-L Imhoff cones averaged/L total suspended solids after 24 hours of settling; but all ponds fell short of meeting an averaged/L total suspended solids after a 2 hour interval which would be ideally achieved for wastewater effluent. No relationship was seen between settling performance and the bacterial content of flocs.
Soluble carbonaceous biochemical oxygen demand (scBOD5) removal by the raceway ponds was sufficient to meet wastewater treatment requirements year around. Influent scBOD5 concentrations averaged 83 mg/L, and the effluent averaged 5.1 mg/L and 4.2 mg/L for the 2-day and 3-day HRT pond sets, respectively.
The variable with the greatest influence on productivity in all pond sets, and settling performance in the recycled water pond set, was season (i.e., co-correlated variables of solar insolation and pond temperature). Neither productivity nor settling appeared to be related to prominent algae genera or prevalence of grazers.
The high net productivity achieved with a growth medium of primary clarifier effluent and the generally high settleability of algal-bacterial flocs indicate a good potential for algae wastewater treatment and biofuel production. However, the settling of algae grown on recycled water needs improvement to achieve the full potential of wastewater-grown algae biofuel production.