Segui questo link per vedere altri tipi di pubblicazioni sul tema: Spt3.
Tesi sul tema "Spt3"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Spt3".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Bhat, Abdul Wajid. "Regulation of transcription elongation factors SPT2 and SPT6 by casein kinase II". Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/29184/29184.pdf.
Testo completoAbstract (sommario):
Comme pour tous les autres processus en lien avec l’ADN, la structure de la chromatine lors de la transcription est dans un état de perpétuel changement. Ainsi, elle est ouverte pour permettre l’accès à l’ADN, pour ensuite se replier correctement. La dynamique de la structure chromatinienne est régulée finement par de multiples mécanismes qui agissent ensemble afin de rendre le processus hautement efficace. Ces mécanismes comprennent les modifications post-traductionelles des histones, le remodelage de la chromatine par les remodeleurs ATP-dépendants, l’incorporation des variants d’histones et l’assemblage/désassemblage des nucléosomes par les chaperons d’histones. En plus de ces activités, il y a un certain nombre de composantes non-reliées aux histones qui sont directement impliquées dans les modulations de la conformation de la chromatine associées à la transcription. Chez la levure, un de ces facteurs est la protéine HMG-like Spt2p, démontrée précédemment comme étant directement impliquée dans le réassemblage des nucléosomes dans le sillon de l’ARN polymérase II en déplacement le long du segment d’ADN transcrit. Dans la présente étude, nous démontrons que Spt2p est phosphorylée directement par la caséine kinase II (CKII) et que cette modification inhibe sa liaison à la chromatine. Nos résultats indiquent que la CKII altère l’interaction de Spt2p avec le chaperon d’histone Spt6p. Nous avons aussi trouvé que la phosphorylation directe de Spt6p par la CKII stimule l’association de ce facteur avec un autre partenaire, Iws1p. Cette association est absolument nécessaire pour le repliement correct des nucléosomes durant l’élongation. De plus, cette régulation positive du complexe Spt6p/Iws1p par la CKII module directement l’association de ce complexe avec la méthyltransférase de H3K36, Set2p. Finalement, nous avons montré que la phosphorylation de Spt6p par la CKII est essentielle à l’inhibition des promoteurs cryptiques et des erreurs de transcription. Dans l’ensemble, nos résultats suggèrent un nouveau mécanisme par lequel la CKII contrôle le repliement correct de la structure de la chromatine dans les régions codantes en modulant les interactions du chaperon d’histone essentiel Spt6p avec ses partenaires Spt2p, Iws1p et Set2p.Like any other DNA-related process, chromatin structure is in a state of constant flux during transcription, unfolded to get access to DNA and refolded back properly. The dynamics of chromatin structure are tightly regulated and multiple mechanisms act together to make the process highly efficient. These include modifications of histones, chromatin remodeling by ATP-dependent remodeling factors, incorporation of histone variants and nucleosome disassembly and reassembly by histone chaperones. In addition to these activities, there are a number of non-histone chromatin components that are directly involved in the modulation of chromatin associated with transcription. In yeast, one of these factors is the HMG-like protein Spt2p previously shown to participate directly in the process of nucleosome reassembly in the wake of RNA polymerase II movement along transcribed DNA. In this work, we show that Spt2p is directly phosphorylated by the casein kinase II (CKII) and we demonstrate that this modification inhibits its association with chromatin. Our findings indicate that CKII disrupts the interaction of Spt2p with the histone chaperone Spt6p. Interestingly, we also found that direct phosphorylation of Spt6p by CKII stimulates the association of this factor with another partner, Iws1p. This association is absolutely required for the refolding of nucleosomes during elongation. Furthermore, this positive regulation of the Spt6p/Iws1p complex by CKII modulates directly the association of this complex with the H3K36 methyltransferase Set2p. Finally, we show that phosphorylation of Spt6p by CKII is essential to the inhibition of cryptic promoters and spurious transcription. Taken together, our results suggest a new mechanism whereby CKII directs chromatin structure refolding in coding regions by modulating the interaction of the essential histone chaperone Spt6p with its partners Spt2p, Iws1p and Set2p.
2
Dürr, Julius [Verfasser], e Klaus [Akademischer Betreuer] Grasser. "The role of the transcription elongation factor SPT4-SPT5 in plant growth and development / Julius Dürr. Betreuer: Klaus Grasser". Regensburg : Universitätsbibliothek Regensburg, 2015. http://d-nb.info/1065445318/34.
Testo completo
3
Vojnić, Erika. "NMR solution structure of the Set2 SRI domain and preparation of RNA polymerase II complexes with the elongation factor Spt4-Spt5". [S.l.] : [s.n.], 2006. http://edoc.ub.uni-muenchen.de/archive/00006976.
Testo completo
4
Vojnic, Erika. "NMR solution structure of the Set2 SRI domain and preparation of RNA polymerase II complexes with the elongation factor Spt4-Spt5". Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-69769.
Testo completo
5
Burckin, Todd A. "Probing the integration of steps in the gene expression pathway through analysis of the SPT4-SPT5 transcription elongation complex in Saccharomyces cervisiae /". Diss., Digital Dissertations Database. Restricted to UC campuses, 2004. http://uclibs.org/PID/11984.
Testo completo
6
MASELLA, MICHEL. "Nouveaux modeles pour traiter les liaisons hydrogene du type o(sp3)---h-o(sp3)". Palaiseau, Ecole polytechnique, 1996. http://www.theses.fr/1996EPXX0020.
Testo completoAbstract (sommario):
Deux nouveaux modeles pour traiter les liaisons hydrogene o(sp3)---h-o(sp3) ont ete developpes. Ils reposent sur une decomposition de l'energie d'interaction en quatre termes: un terme d'echange, un terme electrostatique, un terme de deformation intramoleculaire et une terme de transfert de charge. Ces modeles ont ete parametres a partir de calculs ab initio au niveau mp2/6-311++g(2df,2p). Les deux modeles se distinguent au niveau de l'energie calculee. Le premier modele (appele mitra) evalue une enthalpie de formation a 298 k, le second (appele varuna), une energie d'interaction absolue. Ce dernier modele donnant une bonne evaluation des frequences de vibration des systemes etudies, il permet egalement d'acceder aux enthalpies de complexation a l'aide de relations classiques de la thermodynamiques. Pour appliquer ces modeles, un programme en fortran (sleipnir) a ete ecrit. Ce programme permet de faire des calculs de modelisation moleculaire (bases sur le champ de force mm2 d'allinger), des calculs de frequences de vibration et des calculs de thermodynamique statistique. Ces modeles ont ete appliques aux clusters de l'eau, de l'eau lourde, du methanol ainsi qu'a l'etude des premieres couches de solvatation de petits cationsd monoatomiques (lithium et sodium), et de l'ethane-1,2 diol
7
Holstein, Philipp. "Enantioselective C(sp3)-H Arylation and Development of a Modular C(sp3)-H Alkenylation". Thesis, Lyon 1, 2014. http://www.theses.fr/2014LYO10286.
Testo completoAbstract (sommario):
Récemment, l'activation C-H catalysée par des métaux de transition est devenue un outil performant pour construire des liaisons carbone-carbone et carbone hétéroatome à partir de liaisons C-H omniprésentes dans les molécules organiques. Bien que l'activation des liaisons C-H aromatiques ait été largement étudiée ces dernières années, celle des liaisons C-H aliphatiques représente encore un domaine faiblement exploré. Notre équipe s'est depuis plusieurs années intéressée au développement méthodologique de l'activation C(sp3)-H et à son application en synthèse de produits naturels et molécules bioactives. Dans la continuité des récents travaux sur la version asymétrique de cette réaction, cette thèse décrit le développement et la synthèse de nouveaux ligands du type Binepine. Ces ligands chiraux et monodentates nous ont permis de réaliser la synthèse d'indanes chiraux possédant un centre asymétrique quaternaire, de manière hautement énantio- et diastéréosélective. Cette réaction présente comme avantages l'utilisation d'une faible charge catalytique et d'une température de réaction inférieure à 100 °C, sans aucun additif. Le champ d'application de la réaction inclut notamment l'activation des liaisons C-H d'un groupement méthylène, donnant ainsi accès à des systèmes fusionnés, tricycliques. La construction de molécules non-aromatiques via une alcénylation C-H intramoléculaire a été récemment décrite et s'avère très prometteuse pour la synthèse de produits naturels saturés. Dans la continuité de ces travaux innovants, nous avons développé la synthèse de γ-lactames à partir de bromoalcènes acycliques. Cette nouvelle réaction permet de construire de manière simple et efficace des hétérocycles a cinq chainons de façon modulaire, donnant ainsi la possibilité d'envisager des nouvelles déconnections rétrosynthétiques, complémentaires des méthodes déjà établies. Cette nouvelle méthode a pu être appliquée à la synthèse totale de l'alcaloïde marin Plakoridine A, dont la structure centrale cyclique a été synthétisée en quatre étapes avec un rendement global de 37%Recently, transition-metal-catalyzed C-H activation has emerged as a powerful tool to transform stable C-H bonds into carbon-carbon or carbon-heteroatom bonds. While the activation of aromatic C-H bonds has seen a tremendous development, less effort has been devoted to the more challenging activation of aliphatic C-H bonds. Our group has a long-standing interest in the development of C(sp3)-H activation reactions and their application in the synthesis of natural products and bioactive compounds. In line with previous efforts to develop an asymmetric C(sp3)-H activation, the herein presented work details the synthesis of new Binepine ligands. These monodentate, chiral ligands enabled us to realize a highly dia- and enantioselective C(sp3)-H activation reaction allowing the construction of chiral quaternary carbon centers. Strong points of this robust method are the low catalyst loading, the low reaction temperature and the absence of additives. The substrate scope includes the rare activation of methylene C-H bonds leading to fused tricyclic carbocycles and heterocycles. The construction of non-aromatic molecules through intramolecular C-H alkenylation was recently disclosed and has great potential for the construction of saturated natural products. Based on seminal work, we have developed the synthesis of valuable γ- lactams from acyclic bromoalkenes. This new methodology offers a powerful way to build simple, five-membered N heterocycles in a modular fashion. Notably, it enables a new retrosynthetic disconnection which is complementary to conventional approaches. Finally, we set out to showcase its utility as key step in the total synthesis of the pyrrolidine alkaloid Plakoridine A. The cyclic core structure was accessed in four steps and 37% overall yield
8
Tapias, Soler Alicia. "Regulació del promotor de "Sp3"". Doctoral thesis, Universitat de Barcelona, 2008. http://hdl.handle.net/10803/1059.
Testo completoAbstract (sommario):
Sp1 i Sp3 pertanyen a la família de factors de transcripció Sp que controla la transcripció de gens implicats en gairebé tots els processos cel.lulars. Estudis previs al nostre grup van estudiar la regulació del promotor del gen Sp1 i van demostrar que la transcripció de Sp1 estava regulada principalment de forma positiva per Sp1 i NF-Y, i que Sp3 era capaç de contrarrestar l'activació produïda per Sp1 sobre el seu propi promotor. Donat que la relació Sp1/Sp3 a la cèl·lula és important per a la regulació dels gens diana, en aquest treball ens vam proposar estudiar la regulació del promotor de Sp3.Vam clonar una regió de 546 bp que corresponia al promotor de Sp3 i vam procedir a la seva caracterització. Sp3 presenta múltiples inicis de transcripció localitzats entre les posicions -132 i -70 respecte de l'inici de traducció i la seva màxima activitat promotora es localitza a la regió fins a -281bp respecte de l'inici de traducció. Mitjançant les tècniques de retardament de la movilitat electroforètica (EMSA) i Immunoprecipitació de la Cromatina (ChIP) hem demostrat la unió dels factors Sp1, Sp3, NF-Y, NF-1, c-Myb, B-Myb i c-Jun al promotor de Sp3. D'altra banda hem estudiat l'efecte de la sobreexpressió i la inhibició d'aquestes proteïnes sobre l'activitat d'aquest promotor utilitzant assajos d'activitat luciferasa, i sobre els nivells endògens de mRNA utilitzant RT-Real Time-PCR. Sp3 activa la transcripció del seu propi promotor. El promotor de Sp3 també és activat de forma més potent per Sp1, Sp3 i NF-Y; tot i que NF-1, c-Myb, B-Myb, c-Jun i c-Fos també poden activar aquest promotor. Un altre fet remarcable és que E2F1 es comporta com a repressor del promotor de Sp3. Tots els resultats observats a nivell de l'activitat del promotor es van confirmar amb la mesura dels nivells endogens de mRNA per Sp3.
Addicionalment, s'ha estudiat la interacció de Sp1 amb diferents proteïnes implicades en la regulació del cicle cel·lular i s'ha caracteritzat l'efecte de la seva sobreexpressió sobre l'activitat del promotor de Sp1, ja que està regulat per Sp1. Utilitzant un array d'anticossos, es va fer un cribatge de proteïnes que poguessin interaccionar amb Sp1, i algunes d'elles es van confirmar per co-immunoprecipitació. Això ens va permetre demostrar que Sp1 és capaç d'interaccionar amb CDK4, p21, SKP2 i BRCA2. Posteriorment, vam analitzar l'efecte d'aquestes i altres proteïnes que interaccionen amb Sp1 sobre el promotor de Sp1, i vam observar que el promotor de Sp1 és regulat de forma positiva per la sobreexpressió de CDK4, SKP2, BRCA2, Ciclina D1, E2F1/DP1 i Stat3; mentre que és reprimit per la sobreexpressió de p53 i NFB. Per tal d'analitzar si hi havia una correlació entre els efectes sobre el promotor de Sp1 i una alteració dels nivells endogens de Sp1, vam confirmar tots els efectes observats a nivell de l'activitat del promotor tot emprant la tècnica de RT-Real Time-PCR. A més, els efectes sobre el promotor de Sp1 es produeixen mentre aquestes proteïnes estan unides, directa o indirectament, al promotor tal com van demostrar els assajos de ChIP. També vam estudiar l'efecte de la sobreexpressió d'aquestes proteïnes sobre un promotor que només contenia caixes Sp1 i, en general, vam observar efectes equivalents als observats per al promotor de Sp1. La interacció entre Sp1-p21 va ser objecte d'estudi en més detall i vam determinar que l'expressió de p21 en cèl·lules de fibrosarcoma indueix el promotor de Sp1 així com els nivells de mRNA, però, al mateix temps, indueix la degradació de Sp1.
Com a conclusió final, hem vist que el procés de transcripció és un mecanisme molt complex que involucra un gran número de factors de transcripció, així com d'altres proteïnes que puguin interaccionar amb aquests factors.
Sp1 and Sp3 belong to the Sp family of transcription factors that controls transcription of genes involved in almost all processes in the cell. We performed a detailed analysis of the promoter region of the Sp3 transcription factor, including the identification of its transcriptional start sites and the putative binding sites for transcription factors. Multiple transcriptional starts sites were located at position sranging from -70 to -132 relative to the translational start of the gene. We defined the minimal promoter region cooresponding to 281 bp relative to the translational start. Along the promoter sequence we demonstrated the binding of Sp1, Sp3, NF-Y, NF-1, c-Myb, B-Myb and c-Jun. Moreover, we studied the effect of the overexpression or knocking down of these factors on the Sp3 promoter activity and the endogenous mRNA levels. Sp3 is positively autoregulated and it is also activated by Sp1, NF-Y, Myb, AP-1 and NF-1. On the contrary, Sp3 transcription is repressed by E2F/DP1 overexpression.
Additionally, we studied the interaction of Sp1 with other proteins involved in the cell cycle regulation and we characterized the effect the overexpression of these proteins on the Sp1promoter activity, given that this promoter is regulated by Sp1. Sp1 is able to interact with CDK4, p21, SKP2 and BRCA2. The Sp1 promoter is positively regulated by the overexpression of CDK4, SKP2, BRCA2, Ciclina D1, E2F1/DP1 and Stat3 whereas the overepression of p53 and NFB represses the promoter. The effects of all these proteins were also analyzed at the Sp1 mRNA level and by using an artificial promoter containing only Sp1 binding sites. The interaction between Sp1 and p21 was further analyzed and we demonstrated that, in fibrosarcoma cells, p21 induces the Sp1 promoter and its mRNA expression but, at the same time, it induces the degradation of Sp1 protein.
The process of transcription is a very complex mechanism that involves a great number of transcription factors and other proteins interacting with these factors.
9
Howarth, Clayton. "Motorinformationens roll i SPT-effekten". Thesis, University of Skövde, School of Humanities and Informatics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-940.
Testo completoAbstract (sommario):
Det har visat sig vara bättre att öva in listor med handlingsfraser genom att utföra dem (SPT, subject-performed tasks) än genom att bara läsa dem (VT, verbal tasks). Vid ett återerinringstest visar sig SPT-effekten då försöksdeltagare med SPTs har ett mycket bättre minne av materialet än försöksdeltagare med VTs. En förklaring till fenomenet är att utförandet av handlingsfraserna förser deltagarna med motorinformation. I den här undersökningen testas motorinformationens roll i SPT-effekten på ett sätt som skiljer sig från traditionell SPT-forskning. Försöksdeltagare fick antingen cykla eller använda en joystick för att navigera genom en virtuell värld där ord fanns utplacerade. Minnet för orden testades sedan i ett efterföljande minnestest. Det visade sig att joystickgruppen kunde återerinra sig fler ord än cykelgruppen. Effekten var oväntad och misstänks bero på bättre koncentrationsmöjligheter för joystickgruppen.
10
Walton, Scarlett Maria. "Catalytic functionalisation of sp3 bonds". Thesis, University of Huddersfield, 2017. http://eprints.hud.ac.uk/id/eprint/34344/.
Testo completoAbstract (sommario):
Reported herein is an investigation into palladium-catalysed -allylation employing sulfonamide nucleophiles. Anions of benzylsulfonamides have been shown to react with a series of allyl acetates in the presence of Pd0 catalysts, phosphine ligands and base at room temperature, enabling the synthesis of sp3-functionalised sulfonamides. The developed methodology has allowed access to a library of novel allylated sulfonamides, varying both amine substituent and allylic functionality. In addition, we have applied our methodology to a series of known sulfonamide drug targets, to demonstrate our reaction as a useful late-stage functionalisation tool, whilst populating chemical space. The performed mechanistic study using a stereospecific electrophile confirms benzylsulfonamides behave as soft carbon nucleophiles in the Tsuji-Trost reaction, as a ‘net retention’ of stereochemistry is observed (confirmed by X-ray crystallography). Moreover, the asymmetric synthesis of allylated sulfonamides is probed, although obtaining enantioselectivity a- to SO bonds is naturally difficult, due to the conformational preferences of sulfonamide carbanions. Traditional methods for direct -alkylation of sulfonamides require strong bases, reactive electrophiles, low temperatures and use of stoichiometric amounts of additives. Therefore, in addition to a catalytic method, we report an alternative method reacting benzylsulfonamides with allyl bromide electrophiles via a nucleophilic substitution reaction, using mild conditions (LDA, THF at –20 °C).
11
Dryzhakov, Marian. "Nitro-assisted Brønsted acid catalysis : activation of C(sp3)–O and C(sp3)–F bonds". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAF012/document.
Testo completoAbstract (sommario):
Les alcools sont des partenaires électrophiles attractifs pour des réactions de substitution nucléophile puisque l'eau est le seul sous-produit de la réaction en présence de nucléophiles protiques. Malgré le fait que la réaction soit fortement intéressante, la portée des transformations catalytique reste limitée à une combinaison spécifique alcool/nucléophile, ce qui rend l’emploi d’un ensemble général de conditions catalytiques fortement élusif. Cette thèse décrit le développement d'un système général de catalyse doux pour l'activation d'une large gamme d’alcools π-activés ainsi que d’alcools aliphatiques abordant ainsi les limitations clés dans le domaine. B(C6F6)3•H2O, un acide de Brønsted fort quand il est combiné avec le nitrométhane, a été découvert comme étant un système catalytique idéal pour la substitution chimiosélective d'alcools en présence de fonctionnalités et de groupements protecteurs sensibles aux conditions acides sans le compromis typique entre vitesse de réaction, réactivité substrat/nucléophile et quantité de catalyseur. Plus particulièrement, un effet co-catalytique de composés nitro est décrit pour la réaction d’azidation des alcools aliphatiques tertiaires en employant B(C6F6)3•H2O, permettant, pour la première fois, un turnover catalytique. Sur la base des investigations cinétiques, électroniques et spectroscopiques qui ont été menées, des agrégats de composés nitro et d’acides liés par des intéractions hydrogènes sont proposé comme étant l’espèce catalytiques responsables de la cinétique de la catalyse observée. L'utilité des nouvelles conditions catalytiques a été étendue au-delà de l'activation d'alcool et appliquée au clivage des liaisons fortes C-F dans les réactions de Friedel-Crafts défluorinatives de fluorures aliphatiques tertiairesAlcohols are attractive electrophilic partners for nucleophilic substitution reactions as water is the only by-product in a reaction with protic nucleophiles. Despite being a highly desirable reaction, the scope of useful catalytic transformations remains limited to specific alcohol-nucleophile pairs and a general set of catalytic conditions remains elusive. This thesis describes the development of a general and mild catalyst system for the activation of a broad range of π-activated and aliphatic alcohols to address key limitations in the field. B(C6F6)3•H2O, a strong Brønsted acid, when combined with nitromethane has been found as a widely useful catalyst system for chemoselective alcohol substitution in the presence of acid sensitive functionalities and protecting groups without the typical compromises in reaction rates, substrate/nucleophile scope and catalyst loading. In particular, a co-catalytic effect of nitro compounds is described for the B(C6F6)3•H2O catalyzed azidation of tertiary aliphatic alcohols, enabling catalyst turnover for the first time. On the basis of kinetic, electronic, and spectroscopic investigations, higher order hydrogen-bonded aggregates of nitro compounds and acids are proposed as kinetically competent Brønsted acid catalysts at the origin of the enhanced reactivity. The utility of the new catalytic conditions has been extended beyond alcohol activation and applied to the cleavage of strong C–F bonds in defluorinative Friedel-Crafts reactions of tertiary aliphatic fluorides
12
Belincanta, Antonio. "Avaliação de fatores intervenientes no Índice de Resistência à Penetração do SPT". Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-12062018-162336/.
Testo completoAbstract (sommario):
São salientados neste trabalho de pesquisa alguns pontos importantes da origem, evolução e normatização do ensaio SPT (\"Standard Penetration Test\") no Brasil e no exterior, bem como analisadas variantes, em uso, do método de ensaio proposto pela ABNT (Associação Brasileira de Normas Técnicas), tais como acionamento com cabo de aço e avanço da perfuração feita pela cravação do próprio amostrador, apresentando-se uma avaliação preliminar da influência nos valores dos índices de resistência à penetração N do SPT. Variáveis tidas como de relevância também serão avaliadas, com a quantificação da influência delas, de forma preliminar. Pode-se citar, entre estas variáveis, o tipo do martelo, o dispositivo para queda livre, o uso de roldana móvel, tamanho da cabeça de bater, estado de conservação da composição das hastes e o uso ou não do coxim de madeira. Para a análise e avaliação tanto dos métodos variantes quanto das variáveis intervenientes foram coletados dados em sondagens/ensaios realizados, em quatro cidades de três Estados brasileiros, por seis empresas selecionadas e escolhidas em conformidade aos interesses específicos dos trabalhos. Por fim, são feitas sugestões para continuidade dos trabalhos de pesquisa, visando a melhoria deste tipo de sondagem/ensaio, quanto ao entendimento de suas variáveis, evolução, normatização e, consequentemente, sua padronização.This research work presents some important aspects of the origin, evolution and standardization of the Standard Penetration Test (SPT), both in Brazil and abroad. It will also introduces the currently used variations of the proposed ABNT (Brazilian Association of Technical Standard) test method, which encompass the use of steel rope and drilling advance by sampler driving, and a preliminary evaluation on N values. Finally, it also analyses the influence on N results, of variables such as type of hammer, free weight fall system, use of mobile sheave wheel, size of anvil, state of conservation of sampling rods and use or not of a hard wood cushion. Analysis and evaluation were performed using selected data obtained from six different companies which carried out tests in four cities at three different Brazilian States. Finally suggestions are made for the continuity of research works on this subject aiming SPT test improvement by the understanding of the variables which affect N values which will contribute to its standardization.
13
Bayliss, M. B., J. Ruel, C. W. Stubbs, S. W. Allen, D. E. Applegate, M. L. N. Ashby, M. Bautz et al. "SPT-GMOS: A GEMINI/GMOS-SOUTH SPECTROSCOPIC SURVEY OF GALAXY CLUSTERS IN THE SPT-SZ SURVEY". IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622337.
Testo completoAbstract (sommario):
We present the results of SPT-GMOS, a spectroscopic survey with the Gemini Multi-Object Spectrograph (GMOS) on Gemini South. The targets of SPT-GMOS are galaxy clusters identified in the SPT-SZ survey, a millimeter-wave survey of 2500 deg(2) of the southern sky using the South Pole Telescope (SPT). Multi-object spectroscopic observations of 62 SPT-selected galaxy clusters were performed between 2011 January and 2015 December, yielding spectra with radial velocity measurements for 2595 sources. We identify 2243 of these sources as galaxies, and 352 as stars. Of the galaxies, we identify 1579 as members of SPT-SZ galaxy clusters. The primary goal of these observations was to obtain spectra of cluster member galaxies to estimate cluster redshifts and velocity dispersions. We describe the full spectroscopic data set and resulting data products, including galaxy redshifts, cluster redshifts, and velocity dispersions, and measurements of several well-known spectral indices for each galaxy: the equivalent width, W, of [O II] lambda lambda 3727, 3729 and H-delta, and the 4000 angstrom break strength, D4000. We use the spectral indices to classify galaxies by spectral type (i.e., passive, post-starburst, star-forming), and we match the spectra against photometric catalogs to characterize spectroscopically observed cluster members as a function of brightness (relative to m*). Finally, we report several new measurements of redshifts for ten bright, strongly lensed background galaxies in the cores of eight galaxy clusters. Combining the SPT-GMOS data set with previous spectroscopic follow-up of SPT-SZ galaxy clusters results in spectroscopic measurements for >100 clusters, or similar to 20% of the full SPT-SZ sample.
14
Loeliger, Erin Michelle. "Structure-Function Analysis of the Conserved Histone Chaperone Spt6". Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11369.
Testo completoAbstract (sommario):
Chromatin structure is crucial to regulate access to the genome for processes such as a transcription, recombination, DNA repair, and DNA replication. Spt6, a key factor involved in regulating chromatin structure, is conserved throughout eukaryotes. Spt6 has been shown to function in many aspects of gene expression, including nucleosome assembly, transcription initiation and elongation, and mRNA processing and export. In addition, Spt6 has several conserved domains; however, little is known about their functions. I have performed a structure-function analysis of Spt6 using three separate approaches. First, I employed a random insertion mutagenesis that has identified sixty-seven mutants. While these mutants did not provide information regarding known domains, some have phenotypes that may prove useful for future study. Second, in a collaborative project with Romier lab, I studied the functional roles of the Spt6 SH2 domains. I have shown that deletion of the region of Spt6 encoding the SH2 domains causes severe mutant phenotypes without affecting Spt6 protein levels, demonstrating the importance of the SH2 domains of Spt6. Third, in an additional collaboration with the Romier lab, I showed that mutations that alter the region of Spt6 that interacts with the conserved transcription factor Spn1 impair Spt6 functions in vivo. Overall, this multi-pronged structure-function analysis of Spt6 has provided new insights into the tandem SH2 domains of Spt6, the Spt6-Spn1 interaction, and the uses and limitations of insertion mutagenesis. In addition, I have attempted to explore a possible role for Spt6 in transcription-associated mutagenesis. After employing several types of in vivo assays, I conclude that a possible role for Spt6 in transcription-associated mutagenesis is uncertain, as the results (with respect to a role for Spt6) reproducibly vary depending on the assay used. Thus, understanding this aspect of Spt6 biology awaits better assays and understanding of transcription-associated mutagenesis. Overall, the work in this dissertation will serve to further elucidate the mechanisms of Spt6 in chromatin regulation, transcription, and DNA damage repair.
15
Ng, Iok Tong. "Geotechnical site characterization based on SPT". Thesis, University of Macau, 1999. http://umaclib3.umac.mo/record=b1445031.
Testo completo
16
Odebrecht, Edgar. "Medidas de energia no ensaio SPT". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2003. http://hdl.handle.net/10183/5840.
Testo completoAbstract (sommario):
O presente trabalho apresenta um estudo detalhado da monitoração de energia durante a cravação do amostrador no ensaio SPT, bem como da identificação dos fatores que influenciam estas medidas. Para tanto foi desenvolvido um equipamento para a aquisição dos sinais de força e de aceleração que consta de uma célula de carga, amplificadores e condicionadores de sinais de força e aceleração, sistema de aquisição de sinal e tratamento numérico dos registros. Paralelamente foi implementado um programa embasado na técnica de diferenças finitas que simula numericamente o ensaio, inclusive o balanço das distintas energias ao longo do processo. De posse dessas ferramentas e tecnologia efetuou-se uma extensa campanha de ensaios totalmente controlados. Os resultados da campanha experimental, associados aos fundamentados e princípios básicos da física, permitiram o entendimento do processo de cravação do amostrador no solo com a determinação das perdas (eficiências) ocorridas ao longo do processo e a proposição de uma nova abordagem de interpretação fundamentada no trabalho efetivamente consumido na cravação do amostrador no solo. O conhecimento deste trabalho abre uma gama de alternativas para a estimativa de propriedades de comportamento de solos com base em resultados de medidas de SPT. Exemplos da aplicação destas alternativas são apresentados Ao longo do trabalho verificou-se que: O intervalo de integração utilizado na apropriação da energia deve ser tal que leva em consideração os golpes subseqüentes mesmo em se tratando de hastes longas; A energia assim determinada é dependente da resistência do solo; Existem perdas de energia ao longo das hastes; Estas perdas são diretamente proporcionais ao comprimento das hastes; O ensaio é um fenômeno de grandes deslocamentos e, portanto, deve ser interpretado com a adoção de um referencial fixo e fora do sistema; A variação da energia potencial das hastes deve ser considerada no computo da energia consumida na cravação do amostrador no solo e esta variação da energia é diretamente proporcional à massa das hastes.
17
Bafaluy, Español Daniel. "New Strategies for C(sp3)-H Functionalization". Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670047.
Testo completoAbstract (sommario):
Aquesta tesi descriu innovadors avenços en el camp de la funcionalització oxidativa d’enllaços C-H alifàtics. En aquest sentit, es presenten nous mètodes sostenibles per a la formació d’enllaços C-N i C-F, els quals aconsegueixen vèncer limitacions importants de les tècniques sintètiques actuals. En primer lloc, s’ha descrit una aproximació electroquímica per a la síntesi de pirrolidines i piperidines mitjançant una aminació intramolecular. A través d’aquest protocol, les mateixes condicions experimentals poden ser usades per a la síntesi d’heterocicles tant de cinc com de sis membres. Aquest mètode presenta sostenibilitat i economia atòmica excel·lent, ja que l’hidrogen molecular és l’únic subproducte generat. A continuació, es presenta una innovadora activació d’enllaços N-F per tal de promoure aminacions intramoleculars en posicions alifàtiques. En aquest sentit, es van utilitzar amines fluorades com a fonts de nitrogen efectives en la preparació de pirrolidines i piperidines en el context de la reacció de Hoffmann-Löffler. Ambdós tipus de compostos poden ser obtinguts usant el mateix sistema catalític basat en un complex de CuI. La reacció no necessita additius extra per tal de preparar una gran varietat de productes cíclics amb gran diversitat estructural. El mecanisme de la reacció va ser avaluat exhaustivament a través d’una gran varietat de tècniques fisico-químiques experimentals, així com d’estudis teòrics. Per últim, vam aprofitar el nostre coneixement en l’àmbit de la química de iode i la reacció de Hoffmann-Löffler pel desenvolupament d’una reacció de fluoració alifàtica dirigida sense precedents que utilitza fluor nucleòfil com a font de fluor. La introducció de forma dirigida de iode en una posició alquílica estableix l’escenari per a una segona oxidació que genera una espècie clau de iode hipervalent alquílica. Aquest intermedi crucial que conté el grup supernucleòfug permet l’ús d’un nucleòfil tan modest com el fluorur per a la formació de l’enllaç C-F. La selectivitat pel que fa a la posició funcionalitzada pot ser ajustada amb l’elecció del grup director. Dos grups directors basats en nitrogen es van identificar, mostrant selectivitats complementaries per 1,5- i 1,6-HAT. Això es tradueix en un procediment sintètic uniforme per a la síntesi de 1,3- i de 1,4-fluoroamines.La presente tesis describe avances novedosos en el campo de la funcionalización oxidativa de enlaces C-H alifáticos. En este sentido, se presentan nuevos métodos sostenibles para la formación de enlaces C-N y C-F, los cuales consiguen salvar importantes limitaciones de las técnicas sintéticas actuales. En primer lugar, se ha descrito una aproximación electroquímica para la síntesis de pirrolidinas y piperidinas mediante aminación intramolecular. Mediante este protocolo, las mismas condiciones experimentales pueden ser empleadas para la síntesis de heterociclos tanto de cinco como de seis miembros. Este método presenta una sostenibilidad y economía atómica excelente, ya que hidrógeno molecular es el único subproducto generado. A continuación, se presenta una novedosa activación de enlaces N-F para promover aminaciones intramoleculares en posiciones alifáticas. En este sentido, se emplearon aminas fluoradas como fuentes de nitrógeno efectivas en la preparación de pirrolidinas y piperidinas en el contexto de la reacción de Hofmann-Löffler. Ambos tipos de compuestos pueden ser obtenidos empleando el mismo sistema catalíticos basado en un complejo de CuI. La reacción no necesita de aditivos extra para preparar una gran variedad de productos cíclicos con gran diversidad estructural. El mecanismo de la reacción fue evaluado exhaustivamente a través de una gran variedad de técnicas físico-químicas experimentales, así como a través de estudios teóricos. Por último, aprovechamos nuestro conocimiento en el ámbito de la química de iodo y la reacción de Hofmann-Löffler para el desarrollo de una reacción de fluorinación alifática dirigida sin precedentes que emplea flúor nucleófilo como fuente de flúor. La introducción de forma dirigida de iodo en una posición alquílica establece el escenario para una segunda oxidación que genera una especie clave de iodo hipervalente alquílica. Este intermedio crucial que contiene el grupo supernucleófugo permite el uso de un nucleófilo tan modesto como el fluoruro para la formación del enlace C-F. La selectividad en cuanto a la posición funcionalizada puede ser ajustada con la elección del grupo director. Dos grupos directores basados en nitrógeno fueron identificados, mostrando selectividades complementarias para 1,5- y 1,6-HAT. Esto se traduce en un procedimiento sintético uniforme par
This thesis summarize recent novel advances in the field of oxidative aliphatic C-H functionalization. More sustainable methods for C-N and C-F bond construction are herein presented, each one of those overcoming important limitations of the state-of-the-art stablished technologies. First, an electrochemical intramolecular amination approach toward synthesis of pyrrolidines and piperidines was described. In this novel approach, saturated five- and six-membered ring N-heterocycles can be obtained within the same experimental conditions. From an environmental approach, and outstanding sustainability and atom economy is achieved, since molecular hydrogen is formed as the sole by-product. Subsequently, an unprecedented activation of N-F bonds promoting intramolecular aliphatic amination was developed. In this sense, fluorinated amines were employed as effective transferable nitrogen groups for pyrrolidine and piperidine formation in the Hofmann-Löffler reaction context. The two series of products can be prepared with a unified catalytic system based on a well-defined CuI complex. The reaction occurs without the need of additional additives for smooth synthesis of a wide diversity of cyclized products. The mechanism of the reaction was extensively studied by a plethora of experimental physical organic techniques together with theoretical calculations. Finally, we employed our expertise on iodine chemistry and Hofmann-Löffler reaction for the development of a novel directed C(sp3)-H fluorination reaction which employs simple fluoride as nucleophilic fluorine source. Amine-directed installation of an alkyl-iodine center sets up the scenario for a second oxidation event which generates a key hypervalent alkyl-iodine(III) species. This crucial intermediate bearing the supernucleophuge group allow for the use of a lousy nucleophile such as fluoride for the C-F formation event. The position selectivity can be tuned by selection of the directing group. We identified two amine-based functionalities with complementary 1,5- and 1,6-HAT selectivity. This translates in a direct access to 1,3- and 1,4-fluoroamines within this fast and mild synthetic procedure.
18
Lopes, Mike dos Santos. "Avaliação da eficácia energética no ensaio SPT". Master's thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/2720.
Testo completoAbstract (sommario):
Mestrado em Engenharia GeológicaEsta tese de fim de curso aborda a influência das perdas de energia num dos ensaios de caracterização geotécnica mais usados em todo o mundo, o Standard Penetration Test, mais conhecido como SPT. Essas perdas de energia afectam os resultados do ensaio, sendo que nesta tese, se quantificou a eficácia energética de modo a se tentar perceber a influência dessas perdas nos resultados finais. Para tal, realizou-se uma campanha de três ensaios na Guarda analisando-se posteriormente, com ajuda de software (Pile Driving Analyser), os 163 golpes resultantes da mesma. Nesta campanha para além da medição da energia transferida ao trem de varas, também se avaliou a altura de queda e a velocidade de impacto do martelo, observando-se no final do ensaio a existência de uma diferença entre a energia teórica e a energia medida. ABSTRACT: This graduation’s work addresses the impact of the loss of energy in one of the most used tests of geotechnical characterization throughout the world, the Standard Penetration Test, better known as SPT. These losses of energy affect the test results, so in this graduation’s work we quantified the energy efficiency in order to try to understand the influence of those losses in the final results. To this end, a campaign of three tests was performed in Guarda analyzing later, with help of software (Pile Driving Analyzer), the 163 blows from this campaign. In this campaign beyond the measurement of energy transferred to the poles, we also evaluated the height of fall and the velocity impact of the hammer. Looking at the end of the test that there exists a difference between the theoretical and measure energy.
19
Bawazeer, Wafa Abubaker S. "Tandem reactions for sp3-rich scaffold synthesis". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32195/.
Testo completoAbstract (sommario):
Several novel methodologies were explored with the general purpose of rapid access to molecular complexity and sp3-rich scaffolds. A number of novel scaffolds were successfully synthesised, utilising two-directional synthesis and tandem reactions. The chemistries applied have been demonstrated to be capable of readily fabricating many novel and interesting diverse molecular scaffolds. Indeed, the azaspirocyclic cores found in halichlorine and pinnaic acid were synthesised using this approach starting with ethyl formate. More diverse scaffolds were generated from simple symmetrical linear molecules derived from ethyl formate, utilising the nitrone produced in situ by the treatment of the central ketone with either hydroxylamine hydrochloride or amino acids. These afforded number novel skeletons [A-C], which are expected to have interesting biological activity. In addition, they are conceivably useful skeletons in the synthesis of natural products, or in drug synthesis due to its high saturation (high Fsp3) characters. Using the tandem reactions, we have also managed to develop a rapid synthetic route to an sp3 -rich chemical scaffold [F] derived from novel isoxazolidine scaffold [E]. This project has been published with a contribution of other group member. We were interested to synthesise of some natural products. We tried to explore the possibility of developing an enantioselective synthesis approach to the key intermediate in the synthesis of hippodamine [H], few attempts toward the synthesis of the marine alkaloids phakellin [I]. Several novel applications of chiral sulfinimines were explored. Initially some preliminary results toward the synthesis of piperidine dione [I] were recorded. Successful attempts of tert-butyl sulfinimines with dianion tert-butyl-acetoacetate afforded a range of cyclic compound piperdine dione [J] in a good yield.
20
Aspin, Samuel. "Arylation migratoire C(sp3)-H d'énolates d'esters". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10298.
Testo completoAbstract (sommario):
La fonctionnalisation C(sp3)-H catalysée par des métaux de transitions, ouvre de nombreuses perspectives en synthèse organique, permettant des voies d'accès plus économes en atomes, et en étapes à des molécules à forte valeur ajoutée. Dans cette optique, une méthode efficace permettant l'arylation des liaisons C(sp3)-H en position α d'un groupement attracteur, plus communément appelée α -arylation a récemment fait l'objet d'une attention toute particulière de la part de la communauté scientifique. Le travail détaillé dans ce manuscrit décrit les dernières avancées de cette méthodologie, ainsi qu'une variante «β-arylation » développée au laboratoire qui constitue une évolution significative dans le domaine de l'arylation regiosélective des liaisons C(sp3)-H non activées. Dans le cadre de ce projet de thèse nous nous sommes efforcés de développer cette nouvelle réaction que nous avons pu optimiser pour l'étendre à une famille plus étendue de substrats de type amino-esters. Dans la continuité de ce travail nous avons réalisé la première réaction d'arylation migratoire sélective d'amino-esters pouvant aller jusqu'à la position η d'une chaîne alkyle linéaire. Enfin, dans le but d'accéder à de nouvelles molécules à plus haute valeur ajoutée, nous avons pu appliquer notre méthodologie aux acetals de cétènes silylés permettant de dépasser certaines limitations du système existant. Dans ce cas précis, des conditions plus douces (sans base forte) ont permis l'arylation de substrats dits sensibles et par extension la synthèse de lactones fonctionnaliséesThe transition metal catalysed functionalization of C(sp3)-H bonds unlocks numerous perspectives within organic synthesis in terms of atom economical access routes to otherwise difficult to synthesise molecules. One efficient method to exact such transformations involves the exploitation of an activated C-H bond situated adjacent to an activating electron withdrawing group, allowing facile insertion of a transition metal catalyst species and subsequent functionalization with a new species (normally an aryl group). This strategy is generally termed ‘α-functionalization’. The work detailed within this manuscript describes a diversion from the classic, and well documented α-functionalization reaction, in which rearrangement steps within the catalytic cycle give rise to β- and more remote substrate functionalization. The first new methodology to be described involves a fundamental extension to the in-house developed β-arylation reaction, in which, through careful substrate and ligand choice, this methodology could be applied to achieve the functionalization of simple ester enolates in remote γ- to η - positions. The developed strategy allowed the synthesis of a small range of interesting homophenylalanine analogues, and higher homologues. The second methodology to be described involves a necessary modified protocol for the β-arylation reaction, in which silyl ketene acetals were exploited as mild metal-enolate surrogates, allowing the coupling of base-sensitive substrates. The previously described reaction scope has been extended in terms of both the electrophile and nucleophile coupling partners through the development of mild reaction conditions, which subsequently allowed application of several products towards the synthesis of lactones
21
Morais, Thaise da Silva Oliveira. "Interpretação racional de resultados de ensaios SPT com base em conceitos de energia". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-29022016-111249/.
Testo completoAbstract (sommario):
A sondagem de simples reconhecimento do solo com medida do índice de resistência à penetração dinâmica do amostrador (NSPT), universalmente conhecida como ensaio SPT, é um dos ensaios de campo mais difundidos no Brasil. A popularidade deste ensaio deve-se a sua praticidade, baixo custo, à experiência já adquirida e a fácil utilização dos seus resultados. Entretanto, este ensaio tem sido amplamente criticado devido às variações de equipamentos e procedimentos, que causa dispersões significativas nos resultados. Usualmente, o índice NSPT é utilizado na estimativa da capacidade de carga e recalque de fundações, a partir de correlações empíricas ou semi-empíricas, o que também recebe críticas, visto que essas correlações são baseadas em observações práticas e sem fundamento científico. O índice NSPT é função da quantidade de energia entregue ao amostrador, durante o golpe no ensaio SPT. Assim, o conhecimento da eficiência permite normalizar os valores de NSPT para um valor de referência padrão. O valor padrão adotado internacionalmente, correspondente a uma eficiência de 60%. Desta forma, a análise racional dos resultados de ensaios SPT, concentra-se na estimativa das quantidades de energia envolvidas no ensaio. Neste contexto, o presente trabalho trata da interpretação racional de ensaios SPT realizados com o monitoramento das quantidades de energia envolvidas no ensaio. As energias foram obtidas indiretamente, através de sinais de força e aceleração durante a propagação da onda de tensão pela composição de haste. Para tanto, foram utilizados segmentos de hastes instrumentadas com células de carga e acelerômetros; e um sistema de aquisição de dados indicado para o monitoramento de eventos dinâmicos. Os ensaios SPT foram realizados com instrumentação dinâmica em duas seções ao longo da composição de hastes (topo e base, simultaneamente). Assim, a partir desse arranjo, foram determinadas as quantidades de energia responsáveis pela cravação do amostrador e as perdas ocorridas. A partir dos sinais de força no topo do amostrador, foram determinadas as resistências dinâmicas mobilizadas no sistema solo-amostrador devido à cravação. Estes resultados experimentais foram comparados com resultados teóricos de resistência dinâmica e estática, obtidos com base no Princípio de Hamilton. De posse dos resultados de eficiência, comprimento das amostras recuperadas e do atrito adesão entre a parede externa do amostrador e o solo, foi feito o equilíbrio das reações mobilizadas no amostrador, segundo a proposta de Aoki (2013), sendo obtidas as resistências de ponta e atrito (interno e externo) no sistema solo-amostrador.The Standard Penetration Test (SPT) with measurement of the index of resistance to dynamic penetration of the sampler (NSPT) is one of the most widespread in situ tests in Brazil. The popularity of this test is due to its practicality, low cost, acquired experience by practitioners and simple applicability of its results. However, this test has been widely criticized because of variation in equipment and procedures, which causes significant dispersion in the results. The NSPT index is usually used to estimate the bearing capacity and settlement of foundations, using empirical or semi-empirical correlations. This fact also receives criticism, as these correlations are based on practical observations without any scientific basis. The NSPT index depends on the amount of energy delivered to the sampler, during the blow in the SPT test. Thus, knowing the equipment efficiency allows normalizing the NSPT values to a standard reference value. The international reference value corresponds to an efficiency of 60%. In this way, the rational analysis of the results of SPT tests essentially depends on the estimation of the quantities of energy involved in the test. This research presents the rational interpretation of the SPT test results based on monitoring the amounts of energy involved in the test. The energies were indirectly obtained through force and acceleration signals during the stress wave propagation along the string of rods. For this, rod subassemblies instrumented with load cells and accelerometers were used. A suitable data acquisition system for monitoring dynamic events was also used. The SPT tests were performed with instrumented subassemblies placed at two positions along the string of rods (top and bottom simultaneously). Thus, from this arrangement, the amounts of energy accountable for the sampler penetration and the energy losses occurred were determined. Likewise, the dynamic resistances mobilized in the soil-sampler system during the penetration were determined from the force and acceleration signals at the top of the sampler. These experimental results were compared with those theoretical results, based on the Principle of Hamilton. With the efficiency results, the length of recovered samples and the external skin friction in the soil-sampler system, the balance of the reactions mobilized in the sampler was verified, as proposed by Aoki (2013). Thus, the tip and skin friction (internal and external) resistances in the soil-sampler system were obtained.
22
Rousseaux, Sophie. "Palladium-Catalyzed C(sp2)-C(sp3) Bond Formation". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23058.
Testo completoAbstract (sommario):
Palladium-catalyzed reactions for carbon-carbon bond formation have had a significant impact on the field of organic chemistry in recent decades. Illustrative is the 2010 Nobel Prize, awarded for “palladium-catalyzed cross couplings in organic synthesis”, and the numerous applications of these transformations in industrial settings. This thesis describes recent developments in C(sp2)-C(sp3) bond formation, focusing on alkane arylation reactions and arylative dearomatization transformations. In the first part, our contributions to the development of intramolecular C(sp3)-H arylation reactions from aryl chlorides are described (Chapter 2). The use of catalytic quantities of pivalic acid was found to be crucial to observe the desired reactivity. The reactions are highly chemoselective for arylation at primary aliphatic C-H bonds. Theoretical calculations revealed that C-H bond cleavage is facilitated by the formation of an agostic interaction between the palladium centre and a geminal C-H bond. In the following section, the development of an alkane arylation reaction adjacent to amides and sulfonamides is presented (Chapter 3). The mechanism of C(sp3)-H bond cleavage in alkane arylation reactions is also addressed through an in-depth experimental and theoretical mechanistic study. The isolation and characterization of an intermediate in the catalytic cycle, the evaluation of the roles of both carbonate and pivalate bases in reaction mechanism as well as kinetic studies are reported. Our serendipitous discovery of an arylation reaction at cyclopropane methylene C-H bonds is discussed in Chapter 4. Reaction conditions for the conversion of cyclopropylanilines to quinolines/tetrahydroquinolines via one-pot palladium(0)-catalyzed C(sp3)-H arylation with subsequent oxidation/reduction are described. Initial studies are also presented, which suggest that this transformation is mechanistically unique from other Pd catalyzed cyclopropane ring-opening reactions. Preliminary investigations towards the development of an asymmetric alkane arylation reaction are highlighted in Chapter 5. Both chiral carboxylic acid additives and phosphine ligands have been examined in this context. While high yields and enantiomeric excesses were never observed, encouraging results have been obtained and are supported by recent reports from other research groups. Finally, in part two, the use of Pd(0)-catalysis for the intramolecular arylative dearomatization of phenols is presented (Chapter 7). These reactions generate spirocyclohexadienones bearing all-carbon quaternary centres in good to excellent yields. The nature of the base, although not well understood, appears to be crucial for this transformation. Preliminary results in the development of an enantioselective variant of this transformation demonstrate the influence of catalyst activation on levels of enantiomeric excess.
23
Wang, Anqi. "Cu-Catalyzed Amination of sp3 C-H Bonds". Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/509.
Testo completoAbstract (sommario):
Presented herein is the development, optimization and mechanistic investigation of an Cu catalytic system for the oxidation of sp 3 C-H bond of simple arenes to form C-N bond in a direct manner. Due to the prevalence of nitrogen containing molecules among biologically active synthetic and natural compounds, synthetic chemists have always been motivated to develop new efficient ways to directly transform ubiquitous carbonhydrogen (C-H) bonds into carbon- nitrogen (C-N) bonds. Recent advances in transition metal catalyzed C-H amination has demonstrated that it is not only possible but also practical to functionalize C-H bonds that are often considered inert in one step, circumventing more classical, sequential functional group interconversion approaches. Existing catalytic systems that promote the transition metal-catalyzed, amination of sp 3 C-H bonds displayed certain limitations, especially the lack of built-in versatility and stability in their amination reagents. To overcome these drawbacks of these existing catalytic system, our group developed a new Cu amination protocol that deployed versatile hydroxylamine-based with general structure RSO 2 NH-OAc as amination reagents. Although the reactivity of the catalytic system ranges from moderate to good, the catalytic system provided promising results using simple arene substrates. Further detailed mechanistic studies revealed that the reaction undergoes an unprecedented two subsequent cycles divided by a major intermediate PhCH 2 (NTsOAc). The proposed mechanism is consistent with radical clock experiments, observed reaction profiles, the need for excess of substrate, and the documented role of the ligand in the catalytic system. The exciting proposed mechanism led to a new type of copper catalyzed amination reaction using N- fluorobenzenesulfonimide (NFSI) as oxidant, which overcomes the need to use an excess of substrate. A wide range of unactivated amines HNR 1 R 2 , including sulfonamide and benzamide, can be used as amine sources, which enables the installation of different nitrogen groups on benzylic sp 3 C-H bond of a variety of substrates in moderate to excellent yield. Moreover, mechanistic experiments and critical analysis of related reactivity in the literature provide insight into the catalytic cycle, resulting in a proposal that details the role of both oxidant and amine source in the new system.
24
Abdulla, Othman. "[1,2]-Sigmatropic rearrangement of benzylic ammoniumy lids ; Catalytic sp3-sp3 functionalisation of sulfonamides ; Annulation of arynes in the synthesis of sultams". Thesis, University of Huddersfield, 2018. http://eprints.hud.ac.uk/id/eprint/34758/.
Testo completoAbstract (sommario):
The first chapter in this thesis describes research on the asymmetric [1,2]-sigmatropic rearrangement of benzylic ammonium ylids. Our group previousely developed method showing that DMSO as solvent, and BTPP as base, in the presence of 5Å molecular sieves, dramatically improves the yield of the reaction. Hence, we applied the developed the method using8-(–)-phenylmenthol and (2S)-camphorsultam as chiral auxiliaries. In the second chapter, a new application of Pd-catalysed allylation is reported. This enabled the synthesis of (30)of branched sp3-functionalised sulfonamides, a compound class for which few reported methods exist. By reacting benzyl sulfonamides with allylic acetates in the presence of Pd0 catalysts and a base, at room temperature, direct allylation was efficiently performed, yielding products that are analogues of structural motifs seen in biologically active small molecules. The reaction was performed under mild conditions and could be applied to nanomolar sigma-receptor binders, thus enabling a late-stage functionalisation and efficient expansion of drug-like chemical space. The third chapter described a synthesis of benzosultam without recourse to transition-metal catalysis, or stoichiometric amounts of organometallic building blocks. Iodomethane sulfonylamide adds to benzyne (generated using fluoride sources), and then the formed intermediate undergos an intramolecular cyclisation to afford sultam. Using this method that procceds under simple reaction conditions, (11) benzosultams were synthesised in modest yield.
25
Humphreys, D. "Identification of a novel substrate of the Salmonella protein tyrosine phosphatase SptP". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604780.
Testo completoAbstract (sommario):
A novel cellular target was captured when purified SptP substrate-trapping derivatives and cell extracts were combined, which was isolated and identified by MALDI-TOF mass spectrometry as VCP (valosin-containing protein). VCP is a AAA family ATPase that regulates multiple ubiquitin-dependent cellular processes, including proteasome-dependant protein degradation, protein-membrane association and organelle biogenesis. Next, interaction between native SptP and VCP was reconstituted in vitro. Further biochemical analyses revealed that binding was blocked by phosphatase inhibitors and required both SptP domains (GAP and PTP). Furthermore, SptP exhibited potent phosphatase activity towards VCP in vitro, and TTSS-delivered SptP associated with and specifically dephosphorylated VCP during infection of cultured cells with S. typhimurium. Two additional entry effectors, the Salmonella GTP exchange factor mimics SopE/2 and inositol phosphatase SopB are ubiquitinated following their delivery into target cells. Immunoprecipitation of SopE2 and SopB from cells following infection with a S. typhimurium ΔsptP null mutant localisation occurred independently of SptP and therefore VCP dephosphorylation. Bacterial entry efficiency was unaffected by VCP gene silencing by RNA interference (RNAi), suggesting that SptP-dependent VCP dephosphorylation was relevant later during infection. Such a role was further supported by immunofluorescence and immunoprecipitation analyses demonstrating that SptP persists within infected cells. Immunofluorescence microscopy showed that both SptP and VCP transiently associate with internalised S. typhimurium and that this SptP targeting was dependent upon it s GAP activity. Infection with S. typhimurium engineered to delivery augmented levels of SptP resulted in a 2.1-fold increase in bacterial replication 8-hours post-infection and reciprocally, a 1.7-fold reduction was observed at equivalent time-points after cells were infected with the S. typhimurium ΔsptP mutant. VCP knockdown resulted in increased bacterial replication and parallel immunofluorescence microscopy revealed elevated numbers of Salmonella localised in the infected cell cytosol. Examination of wild-type SCV morphology after VCP knockdown demonstrated that Sif formation was abolished. This thesis reports that the Salmonella entry effector SptP persists after invasion and regulates S. typhimurium replication at late stages of infection through alteration of the phosphorylation status of VCP, a novel cellular target of the SptP PTP domain located on the SCV.
26
Kiely, Christine M. "Spt6 Regulates Transcription and Chromatin Structure in the Fission Yeast, Schizosaccharomyces Pombe". Thesis, Harvard University, 2011. http://dissertations.umi.com/gsas.harvard:10027.
Testo completoAbstract (sommario):
Spt6 is a conserved eukaryotic transcription factor, known to interact with both nucleosomes and RNA polymerase II (RNAPII) to control transcription. We have initiated study of Spt6 in S. pombe in order to identify both novel and conserved roles in regulation of transcription and chromatin. We first constructed and analyzed spt6 mutants by several approaches. As Spt6 is known to be required for histone H3K36 methylation in both Saccharomyces cerevisiae and human cells, we examined the global levels of several histone modifications; we found that in S. pombe, Spt6 is required for both H3K4 and H3K36 trimethylation. We examined the chromatin state at two highly expressed genes, \(act1^+\) and \(pma1^+\), and found that there is a defect in recruitment of the methyltransferases responsible for those marks, Set1 and Set2, respectively. We also observed loss of nucleosomes, as well as a decrease in histone H2B monoubiquitylation. These results suggest that Spt6 plays an important role in chromatin regulation during transcription. We also conducted transcriptional analysis of an spt6 mutant by both microarray and high-throughput sequencing (RNA-seq) and discovered that Spt6 plays a critical role in maintaining the integrity of transcription genome-wide. We found that Spt6 is required to repress antisense transcription, with nearly 70% of genes having antisense transcripts increased by at least two-fold in an spt6 mutant. We also found that transcription of most long terminal repeats (LTRs) is derepressed. Finally, we found that a major class of transcripts elevated in the spt6 mutant is derived from heterochromatin, which is normally silenced. To study the heterochromatic silencing defect in greater detail, we analyzed the chromatin state of the pericentric repeats and found a decrease in H3K9 trimethylation, elevated levels of H3K14 acetylation, reduced recruitment of several known silencing factors and a loss of siRNA production. We also see a very modest increase in RNAPII recruitment. Based on this combination of phenotypes, Spt6 is likely to contribute to both transcriptional and post-transcriptional silencing mechanisms. Taken together, we have found that Spt6 plays several important roles to control transcription in both euchromatin and heterochromatin in S. pombe.
27
Rişchitor, Grigore. "Transcription factor Sp3 as target for SUMOylation in vivo". [S.l. : s.n.], 2005. http://archiv.ub.uni-marburg.de/diss/z2005/0095/.
Testo completo
28
Wappes, Ethan Albert. "Radical sp3 C-H Functionalization of Amines and Alcohols". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555519030868564.
Testo completo
29
Nguyen, Chi Hanh. "Receiver Selection and Calibration Unit for EHT-SPT (RESCUES)". Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/579318.
Testo completoAbstract (sommario):
The Event Horizon Telescope (EHT) uses a technique known as Very Long Baseline Interferometry (VLBI) to combine radio telescopes all over the world into the equivalent of an Earth-size mirror. It will directly image the immediate surroundings of Sagittarius A* (Sgr A*), the supermassive black hole (SMBH) at the center of our galaxy. The 10-m South Pole Telescope (SPT) will provide EHT with its longest baselines, which will significantly improve EHT resolution. To prepare SPT for EHT, a VLBI receiver was built with its own optics system. The third mirror in the system requires a removable and repeatable mount that can rotate, while being light and compact with excellent thermal insulation. In addition, the VLBI receiver needs to have a motorized and remotely-controlled thermal calibration system to aid with data analysis. This project, titled Receiver Selection and Calibration Unit for EHT-SPT (RESCUES), presents a mount design that successfully satisfies the listed requirements. Finite Element Analysis (FEA) predicted that RESCUES had high performance with deformation on the scale of μm, which is within the tolerance of the optics system. Physical tests agreed with FEA simulations, confirming RESCUES reliability. RESCUES was installed at the SPT and first light was detected in 2015.
30
Diebold, Marie-laure. "Etude biochimique, structurale et fonctionnelle du complexe chaperonne d'histone/facteur d'élongation Spt6/Iws1". Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00819618.
Testo completoAbstract (sommario):
Les ARN messagers (ARNm) fonctionnels sont produits au cours d'un mécanisme complexe qui allie la transcription, qui permet la synthèse d'un pré-ARNm, la maturation de ce transcrit et son export. De plus, ces différentes machineries vont devoir faire face à la structure compacte de la chromatine, nécessitant une activité de décondensation/recondensation de la chromatine qui est notamment régulée par les mécanismes épigénétiques. Un très grand nombre de facteurs sont donc requis pour la production des ARNm fonctionnels . Parmi ces facteurs, les protéines Spt6 et Iws1 sont impliquées dans le mécanisme général de la transcription, dans la modulation de la structure de la chromatine et la maturation et l'export des ARNm. Ces travaux de thèse ont permis de caractériser biochimiquement, structuralement et fonctionnellement ces deux protéines, leur complexe et leur interaction avec d'autres effecteurs de la transcription. Ces travaux ont notamment permis de comprendre en termes moléculaires et fonctionnels (i) comment Spt6 est recrutée par l'ARN polyméraseII au cours de la transcription et (ii) comment le complexe Spt6/Iws 1 est formé. Ils ont également permis d'identifier de nouveaux interactants potentiels de Spt6, et notamment le facteur d'élongation de la transcription TFIIS. Ces travaux ont ainsi permis de révéler le rôle essentiel et extrêmement complexe joué par Spt6 et Iws1 lors de la production d'un ARNm, mais également de permettre l'étude future de leur interaction avec d'autres facteurs transcriptionnels.
31
Lanoue, Edith. "Co-expression de la pro-protéine convertase SPC3 et du précurseur neuroendocrinien proSAAS". Mémoire, Université de Sherbrooke, 2001. http://savoirs.usherbrooke.ca/handle/11143/3278.
Testo completoAbstract (sommario):
Les pro-protéines convertases de type subtilisine (SPCs) sont une famille d'enzymes de type sérine protéinases. Les convertases sont impliquées dans la maturation de diverses hormones et protéines sécrétées via leur clivage en C-terminal d'une paire de résidus d'acides aminés basiques de type (RXXR). Jusqu'à tout récemment, un seul inhibiteur naturel des convertases était connu, le neuropeptide 7B2. Ce neuropeptide démontre une activité hautement inhibitrice en son domaine C-terminal. Cette activité inhibitrice agit sur la convertase SPC2. Par contre, ce neuropeptide est également considéré comme bi-fonctionnel puisque son domaine N-terminal est important pour l'activation du potentiel enzymatique de SPC2. Un nouveau précurseur peptidique ressemblant aux granines, une famille de peptides impliqués dans le triage d'hormones et d'enzymes vers les voies de sécrétions, a récemment été identifié, caractérisé et nommé proSAAS. Ce peptide possède une activité spécifique inhibitrice sur SPC3 in vitro . Pour exercer une telle activité inhibitrice in vivo , il est important de démontrer que SPC3 et proSAAS sont co-localisés. Pour y arriver, nous avons étudié l'expression de proSAAS et SPC3 dans le système nerveux central de rat et divers tissus périphériques de type endocrinien et non-endocrinien. Cette expression a été étudiée par la méthode d'hybridation in situ . Nos résultats démontrent que tout comme 7B2, proSAAS est distribué de façon pan neuronal. En périphérie, proSAAS est un excellent marqueur des cellules endocriniennes. Nos études de double marquage ont permis de montrer que l'expression de SPC3 est pratiquement toujours accompagnée de celle de proSAAS. Par contre, l'expression de proSAAS est aussi retrouvée dans des cellules endocrines et des neurones n'exprimant pas SPC3 proposant la possibilité pour proSAAS d'avoir plusieurs fonctions autre que la modulation de l'expression de SPC3.
32
Fielden, D. J. "The role of Spt4/5 and the search for antitermination complexes in archaea". Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1455740/.
Testo completoAbstract (sommario):
Spt4/5 and its bacterial homologue NusG are the only known universally conserved RNAP- associated transcription elongation factors. In the hyperthermophilic archaeon Methanocaldococcus jannaschii, Spt5 comprises an N-terminal NGN domain and a C-terminal KOW domain, and is bound at its NGN domain by Spt4. NusG and Spt5 increase the processivity of RNAP by binding to the RNAP clamp via the NGN domain. This maintains the RNAP clamp in a closed conformation, thereby enabling RNAP to remain bound to the template DNA. The NusG KOW domain interacts with ribosomes, thereby coupling transcription to translation. The functions of Spt4/5 in archaea are less well characterised. The work contained within this thesis demonstrates that in the context of M. jannaschii cell extract, Spt4/5 is found in the same fractions as ribosomes and RNAP, and therefore has the potential to couple transcription and translation. Furthermore, data obtained by microscale thermophoresis suggests that the KOW domain of Spt5 interacts with purified ribosomes. Electron paramagnetic resonance was performed on Spt4/5, demonstrating that Spt5 is conformationally flexible, and that the presence of Spt4 restricts its mobility. Limited proteolysis and thermofluor assays support the notion that Spt4 stabilises the Spt5 NGN domain. In E. coli, NusA binds to RNAP as a component of the antitermination complex, along with NusG, NusB, and NusE. This enables RNAP to enter a pause and termination-resistant state. M. jannaschii NusA consists of two KH domains. Mutational analysis identified the contribution of the two KH domains to RNA binding and identified additional residues involved in the interaction. Archaeal NusA does not coelute with RNAP, raising the possibility that archaeal NusA does not have antitermination functions. In summary this thesis argues that Spt4/5 likely couples transcription and translation in archaea and indicates that archaeal NusA binds to RNA via a novel binding site.
33
Carmo, Maxweel Silva. "Mirador II - Uma Extensão da Ferramenta Mirador para Monitoramento e Gerenciamento do SPP3". Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-01032018-085559/.
Testo completoAbstract (sommario):
A utilização de arquiteturas paralelas MIMD na resolução de problemas que exigem alta demanda computacional tem sido cada vez mais frequente. A máquina paralela SPP2 surge neste cenário como uma arquitetura alternativa, oferecendo alto poder computacional a baixo custo através da utilização de componentes de hardware amplamente disponíveis. Visando facilitar a interação dos usuários com o SPP2, novos mecanismos foram implementados, resultando na máquina paralela SPP3. Para realizar o monitoramento e gerenciamento da máquina paralela SPP2 desenvolveu- se a ferramenta Mirador. Execução remota, gerenciamento de usuários, monitoramento de carga de CPU e memória, monitoramento e gerenciamento da execução de processos, são algumas de suas características. A ferramenta Mirador, quando comparada com outras ferramentas do gênero, apresenta peculiaridades que a colocam em posição de destaque, motivando a continuidade de seu desenvolvimento. O presente trabalho leva adiante o desenvolvimento da Mirador, suprimindo certas deficiências e especificando novas funcionalidades que vão de encontro às necessidades de monitoramento e gerenciamento da máquina paralela SPP3. A ferramenta Mirador II, como resultado deste trabalho, apresenta melhor desempenho e maiores facilidades de interação com o usuário, em relação à sua antecessora. A Mirador II disponibiliza também mecanismos de monitoramento das redes de conexão de alta velocidade Myrinet, mecanismos de gerenciamento autônomo dos nós da máquina paralela e dispositivos de monitoramento via hardware, dentre outras características.The use of MIMD parallel architectures to solve problems that require high computational power has been more and more frequent. The SPP2 parallel machine was developed as an architecture alternative offering high computional power at low cost, using hardware components commonly available. In order to facilitate the interaction between the user and the SPP2, new mechanisms were developed resulting in the SPP3 parallel machine. The Mirador tool was developed to allow the monitoring and management of the SPP2 parallel machine. Remote execution, user management, CPU and memory monitoring, processes execution, monitoring and management are among its main features. The Mirador tool compares very well against similar tools. This has motivated its development. This work continue the development of the Mirador tool, suppressing its main problems and introducing new features to aim at the needs for monitoring and management of the SPP3 parallel machine. The Mirador II tool, as a result of this work, presents better performance and better interaction with the user than its predecessor. The Mirador II makes avaliable monitoring mechanisms for Myrinet network, autonomous management of the parallel machine nodes and devices for hardware monitoring, among another features.
34
Youdell, Michael. "The role of Spt6 and histone H3 lysine 36 methylation in mRNA production". Thesis, University of Oxford, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670030.
Testo completo
35
Diebold, Marie-Laure. "Etude biochimique, structurale et fonctionnelle du complexe chaperonne d'histone/facteur d'élongation Spt6/Iws1". Thesis, Strasbourg, 2012. http://www.theses.fr/2012STRAJ008/document.
Testo completoAbstract (sommario):
Les ARN messagers (ARNm) fonctionnels sont produits au cours d'un mécanisme complexe qui allie la transcription, qui permet la synthèse d'un pré-ARNm, la maturation de ce transcrit et son export. De plus, ces différentes machineries vont devoir faire face à la structure compacte de la chromatine, nécessitant une activité de décondensation/recondensation de la chromatine qui est notamment régulée par les mécanismes épigénétiques. Un très grand nombre de facteurs sont donc requis pour la production des ARNm fonctionnels . Parmi ces facteurs, les protéines Spt6 et Iws1 sont impliquées dans le mécanisme général de la transcription, dans la modulation de la structure de la chromatine et la maturation et l'export des ARNm. Ces travaux de thèse ont permis de caractériser biochimiquement, structuralement et fonctionnellement ces deux protéines, leur complexe et leur interaction avec d'autres effecteurs de la transcription. Ces travaux ont notamment permis de comprendre en termes moléculaires et fonctionnels (i) comment Spt6 est recrutée par l'ARN polyméraseII au cours de la transcription et (ii) comment le complexe Spt6/Iws 1 est formé. Ils ont également permis d'identifier de nouveaux interactants potentiels de Spt6, et notamment le facteur d'élongation de la transcription TFIIS. Ces travaux ont ainsi permis de révéler le rôle essentiel et extrêmement complexe joué par Spt6 et Iws1 lors de la production d'un ARNm, mais également de permettre l'étude future de leur interaction avec d'autres facteurs transcriptionnelsProduction of functional messenger RNA (mRNA) requires a complex mechanism that couples transcription with maturation and export of the mRNA. In addition to this mechanism, chromatin needs to be unwound to allow the transcription machinery access the DNA, this unwinding being also highly regulated. Thus, production of a functional mRNA requires a huge number of factors implicated in these different processes. Among these proteins Spt6 and Iws1 are participating in the mechanism of transcription, chromatin unwinding, and maturation and export of the mRNA. The work carried out during this thesis has enabled the biochemical, structural and functional characterization of these proteins, their complex and their interaction with other effectors of transcription. This work has specifically enabled the molecular and functional characterization (i) of the recruitment of Spt6 by RNA polymerase II and (ii) of the formation of the Spt6/Iws1 complex. Moreover, this work has identified putative new partners of Spt6, not ably the elongation factor TFIIS. Thus, our work has highlighted the essential and complex role of Spt6 and Iws1 during the production of functional mRNA, and has also enabled future studies of the complexes formed by these two proteins with other transcriptional factors
36
Lanoue, Edith. "Co-expression de la pro-protéine convertase SPC3 et du précurseur neuroendocrinien proSAAS". Sherbrooke : Université de Sherbrooke, 2001.
Cerca il testo completo
37
Flores, Livas José. "Computational and experimental studies of sp3-materials at high pressure". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10127.
Testo completoAbstract (sommario):
Nous présentons des études expérimentales et théoriques de disiliciures alcalino-terreux, le disilane (Si2H6) et du carbone à haute pression. Nous étudions les disiliciures et en particulier le cas d’une phase plane de BaSI2 qui a une structure hexagonale avec des liaisons sp3 entre les atomes de silicium. Cet environnement électronique conduit à un gaufrage de feuilles du silicium. Nous démontrons alors une amélioration de la température de transition supraconductrice de 6 à 8.9 K lorsque les couches de silicium s’aplanissent dans cette structure. Des calculs ab initio basés sur DFT ont guidé la recherche expérimentale et permettent d’expliquer comment les propriétés électroniques et des phonons sont fortement affectés par les fluctuations du flambage des plans de silicium. Nous avons aussi étudié les phases cristallines de disilane à très haute pression et une nouvelle phase métallique est proposé en utilisant les méthodes de prédiction de structure cristalline. Les températures de transition calculées donnant un supraconducteur autour de 20 K à 100 GPa. Ces valeurs sont significativement plus faibles comparées à celles avancées dans la littérature. Finalement, nous présentons des études de structures de carbone à haute pression à travers une recherche de structure systématique. Nous avons trouvé une nouvelle forme allotropique du carbone avec une symétrie Cmmm que nous appelons Z-carbone. Cette phase est prévue pour être plus stable que le graphite pour des pressions supérieures à 10 GPa. Des expériences et simulation de rayon-X et spectre Raman sugèrent l’existence de Z-carbone dans des micro-domaines de graphite sous pressionWe present experimental and theoretical studies of sp3 materials, alkaline-earth-metal (AEM) disilicides, disilane (Si2H6) and carbon at high pressure. First, we study the AEM disilicides and in particular the case of a layered phase of BaSi2 which has an hexagonal structure with sp3 bonding of the silicon atoms. This electronic environment leads to a natural corrugated Si-sheets. Extensive ab initio calculations based on DFT guided the experimental research and permit explain how electronic and phonon properties are strongly affected by changes in the buckling of the silicon plans. We demonstrate experimentally and theoretically an enhancement of superconducting transition temperatures from 6 to 8.9 K when silicon planes flatten out in this structure. Second, we investigated the crystal phases of disilane at the megabar range of pressure. A novel metallic phase of disilane is proposed by using crystal structure prediction methods. The calculated transition temperatures yielding a superconducting Tc of around 20 K at 100 GPa and decreasing to 13 K at 220 GPa. These values are significantly smaller than previously predicted Tc’s and put serious drawbacks in the possibility of high-Tc superconductivity based on silicon-hydrogen systems. Third, we studied the sp3-carbon structures at high pressure through a systematic structure search. We found a new allotrope of carbon with Cmmm symmetry which we refer to as Z-carbon. This phase is predicted to be more stable than graphite for pressures above 10 GPa and is formed by sp3-bonds. Experimental and simulated XRD, Raman spectra suggest the existence of Z-carbon in micro-domains of graphite under pressure
38
Rocha, Breno Padovezi. "Emprego do ensaio SPT sísmico na investigação de solos tropicais". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-28112013-100232/.
Testo completoAbstract (sommario):
O principal objetivo deste trabalho é avaliar a aplicação da técnica híbrida de SPT Sísmico (S-SPT), ou seja, a realização da sísmica up-hole em conjunto com a sondagem de simples reconhecimento com medida de SPT, para uma melhor caracterização de solos tropicais. O ensaio híbrido mais empregado para determinação de parâmetros dos solos, inclusive o módulo de cisalhamento máximo (Go) é o de cone sísmico (SCPT). No entanto, sua realização exige equipamentos especiais e de custo elevado. A possibilidade de medir a velocidade de propagação da onda S (VS) em conjunto com o ensaio SPT empregando o a técnica up-hole é uma alternativa interessante. Essa técnica combinada, pouco empregada no Brasil, foi recentemente desenvolvida e testada. Neste trabalho, a determinação ao mesmo tempo e no mesmo furo dos valores de N do SPT e velocidade de onda S (Vs) permitiu calcular o módulo de cisalhamento máximo (Go) e avaliar as vantagens de se obter a relação Go/N, similar a relação entre Go/qc, para investigação de solos tropicais colapsíveis. As áreas de estudo são os campos experimentais da UNESP-Bauru, USP-São Carlos e UNICAMP-Campinas, onde ensaios S-SPT foram realizados. Os resultados desses ensaios foram comparados com valores de VS referência, determinados através de ensaios sísmicos cross-hole, down-hole e SCPT. A diferença entre os valores de VS foram, em média, 8,5, 9,0% e 16,0% respectivamente para os campos experimentais da UNESP-Bauru, USP-São Carlos e UNICAMP-Campinas. Considera-se que a técnica híbrida do S-SPT pode ser empregada para obter o perfil de Go, em conjunto com o ensaio SPT, rapidamente e a um custo relativamente baixo. Constatou-se que a relação Go/N é maior na camada de solo laterítico, e que ela diminui quanto menos evoluído é o perfil do subsolo. Observou-se essa a mesma tendência nos ensaios S-SPT, porém com menor nitidez. Este fato pode estar associado a maior dificuldade de interpretar os registros de ondas sísmicas pela técnica up-hole bem como pela variabilidade do perfil dos subsolos.The main objective of this work is to assess the applicability of the hybrid test, the Seismic SPT (S-SPT), i.e. the up-hole seismic test carried out together with SPT test, in order to achieve a better site characterization of tropical soils. The most used hybrid test to determine the soil parameters, including the maximum shear modulus (Go), is the seismic cone test (SCPT). The possibility of measuring the S wave velocity together with the SPT test using the up-hole technique is an interesting alternative. This combined technique was scarcely used in Brazil and it has been recently developed and tested. In this work, the concomitant measuring of the SPT N value together with the S wave velocity in the same test allowed calculating the maximum shear modulus (Go) and assessing the advantages of obtaining the Go/N ratio, similar to the Go/qc ratio, for the site characterization of tropical collapsible soils. The research areas are the experimental sites of UNESP-Bauru, USP-São Carlos and UNICAMP-Campinas, where SPT tests were carried out. The results of these tests were compared with reference values VS, which were determined via cross-hole, down-hole and SCPT tests. The differences between VS values were, in average, 8.5%, 9.0% and 16.0% respectively for UNESP-Bauru, USP-São Carlos and Campinas-UNICAMP research sites. The hybrid S-SPT test can be used to define the Go profile, together with the N SPT values, with a relatively low cost. It was found that the Go/N ratio is higher in the lateritic soil layer and it gets lower as the soil profile is less developed. The same tendency was observed with the S-SPT tests, however with less distinctness. This fact can be associated to a higher difficulty on the interpretation of seismic wave traces with the up-hole technique as well as to soil variability.
39
Jerhaoui, Soufyan. "Sulfoxydes : novel strategy for the asymmetric C(sp3)-H activation". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF025/document.
Testo completoAbstract (sommario):
Pendant de nombreuses années, les liaisons C-H aliphatiques ont été considérées comme dormantes, difficilement exploitables dans le contexte de la chimie organique. Le défi le plus important est de sélectionner une liaison C-H parmi toutes celles que contient une molécule. L’approche la plus utilisée à ce jour est l’utilisation d’un groupement directeur qui permet, en se liant à un métal, de diriger l’activation d’une liaison C-H en particulier. Suite au développement des groupements bicoordinants, nous avons développé notre propre groupement bicoordinant chiral. Cet auxiliaire nous a permis de réaliser de nombreuses transformations diastéréosélectives sur des carbones aliphatiques telles que l'arylation et l'oléfination. Nous l’avons également utilisé pour développer une méthodologie innovante pour la synthèse de produits naturels. Suite à ces travaux, nous avons développé un nouveau ligand chiral qui a été utilisé dans l’arylation et l’alkynylation énantiosélectives de cycloalcanesOver the decades, non-activated C-H bonds have been considered as dormant functionalities, hardly exploitable in the context of multistep synthesis of complex scaffolds. The main challenge is to select one C-H bond among all contained in one molecule. To answer to this problem bicoordinating directing groups allowing directed C(sp3)-H activation have been developed. Following the work of Daugulis and Babu, we developed our own chiral bicoordinating directing group, (S)-2-(p-tolylsulfinyl)aniline. This chiral auxiliary allowed us to realise various diastereoselective transformations on aliphatic chains such as arylation, olefination oracetoxylation. We also used it to develop a brand-new methodology for the total synthesis ofcyclopropane-bearing natural products. Moreover we developed a new chiral sulfinyl ligand, N-((S)-1-(4-(tert-butyl)phenyl)-2-((R)-p-tolylsulfinyl)ethyl)acetamide, that has been used for the enantioselective arylation and alkynylation of cycloalkanes
40
Perez, Waldo Flores, Jorge Chavez Cerdena, Gary Duran Ramirez e Maggie Martinelli Montoya. "Correlation of dynamic probing light (DPL) and standard penetration test (SPT) for sandy soil of alluvial origin". Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656568.
Testo completoAbstract (sommario):
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.In geotechnical studies, the dynamic probing light (DPL) turns out to be an alternative method to the Standard Penetration test (SPT) for the determination of soil parameters. The requirement of various regulations for correlating both tests in the same field and not establishing a methodology to carry it out, limits the practical scope of dynamic probing light. Thus, this research presents a correlation methodology between the dynamic probing light (DPL) and the Standard Penetration test (SPT) specifically for sandy soils (SP and SP-SM) located in an area of Chilca, located in Cañete. - Lima Peru. For the analysis, more than 400 data pairs were used, obtaining two linear correlations between the count blow of Standard Penetration-NSPT test and the dynamic probing light method-N10, which presented an adjustment correlation between 84% and 87 %.
41
Sumida, Yuto. "Studies on New Synthetic Reactions via sp3C-sp3C Bond Cleavage under Transition Metal Catalysis". 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/120875.
Testo completo
42
Schmidt, Gabriele. "Identifizierung potentieller Zielgene des Transkriptionsfaktors Sp3 in vitro und in vivo". [S.l.] : [s.n.], 2004. http://archiv.ub.uni-marburg.de/diss/z2004/0612/.
Testo completo
43
Lukiantchuki, Juliana Azoia. "Interpretação de resultados do ensaio SPT com base em instrumentação dinâmica". Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-24052013-103725/.
Testo completoAbstract (sommario):
O ensaio de simples reconhecimento do solo (SPT) e usualmente utilizado para estimar a resistência do solo, atraves do índice NSPT, que representa a resistencia a penetração dinâmica do amostrador no solo. Esse índice é usado diretamente em correlações empíricas ou semi-empíricas na determinação da capacidade de suporte e recalque das fundações. Entretanto, esse ensaio tem sido alvo de críticas devido a utilização dessas correlações empíricas, geralmente baseadas em observações práticas e sem nenhum fundamento científico. Críticas também estão relacionadas com a dispersão dos resultados, devido a utilização de diferentes tipos de equipamentos e procedimentos executivos. O índice NSPT depende da parcela de energia que e efetivamente transmitida ao amostrador durante a queda do martelo. Assim, análises racionais dos resultados de ensaios SPT dependem essencialmente da estimativa da quantidade dessa energia. Por esse motivo, tem sido desenvolvidas diversas pesquisas relacionados com a energia envolvida no ensaio SPT. Este trabalho apresenta interpretações dos resultados do ensaio SPT a partir das quantidades de energia envolvidas durante a queda do martelo. Essas quantidades de energia são determinadas indiretamente, através dos sinais de força normal e aceleração durante a propagação da onda de tensão ao longo da composição de hastes. Para isso, foi desenvolvido um equipamento que inclui uma instrumentação capaz de registrar esses sinais de força normal e aceleração. Uma série de ensaios SPT foi realizada com instrumentação instalada tanto no topo como na base da composição de hastes. Esse arranjo permitiu estimar as quantidades de energia disponíveis no topo e na base da composição de hastes. Assim, foi possível determinar a eficiência dos equipamentos SPT com base na quantidade de energia que efetivamente atinge o amostrador. A partir dos sinais registrados, também foi possível determinar a resistência dinâmica mobilizada no sistema solo-amostrador. Os resultados experimentais foram comparados com resultados obtidos através de métodos teóricos, baseados no Princípio de Hamilton, para a determinação da resistência estática e dinâmica do solo. Essas análises mostraram que equações teóricas podem ser adequadas para a determinação da resistência do solo, desde que seja considerada a quantidade de energia que efetivamente atinge o amostrador. Desta forma, essas equações teóricas podem ser facilmente incorporadas na prática de projeto de fundações, contribuindo para o desenvolvimento de métodos baseados na quantidade de energia necessária para a penetração do amostrador no solo.The standard penetration test (SPT) is usually used to estimate the soil strength through the NSPT index which represents the dynamic reaction force of the sampler penetration into the soil. This index is directly used in empirical or semi-empirical correlations for the determination of the bearing capacity and foundation settlements. However, this test has been criticized due to the use of these empirical correlations, often based on practical observation without any scientific basis. Criticism is also related to result dispersion due to the use of different types of equipment and execution procedures. The NSPT index depends on the amount of energy that is effectively transmitted to the sampler during the hammer fall. Thus, rational analyses of the SPT test results essentially depend on the estimation of this amount of energy. For this reason, several studies related to the energy involved in SPT test have been developed. This research presents interpretations of the SPT test results from the amounts of energy involved during the hammer fall. These amounts of energy are indirectly assessed by means of normal force and acceleration signals during the stress wave propagation along the string of rods. For this reason, a device that includes instrumentation capable of registering these signals of normal force and acceleration was developed. A series of tests was performed with the instrumentation installed at the top and the bottom of the string of rods. This arrangement allowed estimating the amount of energy available at the top and bottom of the string of rods. Thus, it was possible to estimate the efficiency of the SPT equipment basing on the amount of energy that actually reaches the sampler. From the recorded signals, it was also possible to assess the dynamic reaction force mobilized in the soil-sample system. The results were compared with other results obtained by theoretical methods, based on the Hamilton´s Principle, for evaluating the static and dynamic reaction force of the soil. These analyzes have shown that theoretical equations may be suitable for the determination of the soil strength, provided that the amount of energy that actually reaches the sampler be considered. Thus, these theoretical equations can be easily incorporated into the practice of foundation designs contributing to the development of methods based on the amount of energy required for the penetration of the sampler into the soil.
44
Tarantino, Giulia. "Catalytic methodologies for C(sp3)-F bond formation with heterogeneous catalysts". Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/111540/.
Testo completoAbstract (sommario):
Fluorinated compounds are extremely desirable in several fields of the chemical industry, such as pharmaceuticals, materials and agrochemicals. Consequently, the development of novel methods of fluorination represents a major challenge in contemporary chemistry. Although several breakthroughs have been achieved in this area in recent years, the development of an active, stable, reusable and truly heterogeneous catalyst, able to perform selective C(sp3)-F formation, has not yet been achieved. Accordingly, this thesis explores the applicability of heterogeneous catalysts, to perform novel and selective C(sp3)-F bond formations. Different strategies to achieve C(sp3)-F bond synthesis were explored, including: i) fluorination of preactivated substrates (e.g. carboxylic acids), and ii) direct C(sp3)-H fluorination. Firstly, the applicability of heterogeneous materials, such as AgxO/TiO2 and pure TiO2, were investigated for decarboxylative fluorination reactions (R-COOH → R-F), with (photofluorination) and without the employment of light sources. Following an investigation of the catalytic performances of AgxO/TiO2 and pure TiO2 for fluorination of pre-activated substrates, an alternative route, whereby the applicability of heterogeneous materials for direct C(sp3)-H fluorination, was explored. Although more elegant and desirable, direct C(sp3)-H fluorination represents an immense challenge, mainly due to the scarce substrate reactivity, which typically results in a requirement of harsher reaction conditions. Due to the challenges associated with activation of C(sp3)-H bonds, two different systems to achieve direct C(sp3)-H fluorination were investigated. Firstly, the viability of benzylic fluorinations was explored, as these substrates represent excellent model substrates with slightly activated C-H bonds. Secondly, substrates possessing less active C(sp3)-H bonds, such as cyclooctane, were investigated for direct alkane fluorination.
45
Aktas, Yusuf. "Application Of Active Sampling And Sptd/gc-ms Analysis Methodologies For Terpenes At Uludag Mountain". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/2/1045368/index.pdf.
Testo completoAbstract (sommario):
Measurement of monoterpenes includingalpha-pinene, camphene, beta-pinene, d-limonene, gamma-terpinene, linalool, 1-isopulegol, 1-borneol, dl-menthol, alpha-terpineol, dihydrocarveol, citronellol, pulegone, geraniol
and gas phase inorganic pollutants (O3 and NOx) were investigated on Uludag Mountain, which is the highest point in North-west Turkey. The sampling site (1645 m altitude) is surrounded by mainly Uludag fir, which is characteristic to Uludag, while altitudes lower than 1000 m were composed of mixed deciduous trees. Sampling apparatus and sampling strategy for collection of the studied terpenes on Uludag Mountain were developed. Breakthrough Volume experiments were performed for accurate sampling. Samples were collected in a field campaign performed during October 2002 by means of active sampling onto glass coated stainless steel tubes containing Tenax&
#61666
TA (55 mg) and Carbopack&
#61652
B (65 mg). The mass flow rate and duration of sampling were 30 mL/min and 4 hours. Short-Path-Thermal-Desorption/Gas Chromatography-Mass Spectrometer (SPTD/GC-MS) was used for the analysis of monoterpenes during 12-14 October 2002. The cryogenic preconcentration (-40oC) was maintained by liquid CO2. HP-1-MS capillary column provided good resolution of peaks, except for pulegone and citronellol at standard operation procedure. Internal standard calibration was applied by adding carefully measured spikes of fenchone to the samples and standards. The detection limits for each terpene were found to be at sub-ppbv level. Daily intermediate standard measurements and auto-tune provided checking the instrumental capabilities. Selected Ion Monitoring mode was used for analysis of the terpenes. For quantitation of the spectra at least one qualifier ion was expected to be within 80% correlation with target ion. Alpha-pinene, camphene, beta-pinene, and d-limonene were determined. The average concentrations of monoterpenes were found to be 0.385, 0.168, 0.111, and 0.204 ppbv respectively. Simultaneous measurements of O3, NOx, SO2, and meteorological parameters were also performed. The data resolution was 15 min for each pollutant. Ozone displayed strong diurnal variation (around 5-30 ppb), while NOx concentrations were almost constant around 15 ppb. During the sampling campaign terpenes showed similar behaviours with O3, but not with NOx. Terpenes had a direct relation with temperature and relative humidity.
46
Thebault, Philippe. "Le facteur d'élongation SPT2/SIN1 est impliqué dans l'assemblage du nucléosome couplé à la transcription". Thesis, Université Laval, 2009. http://www.theses.ulaval.ca/2009/26726/26726.pdf.
Testo completo
47
Lee, Wai-ming. "Correlation of PCPT and SPT data from a shallow marine site investigation /". View the Table of Contents & Abstract, 2004. http://sunzi.lib.hku.hk/hkuto/record/B30110385.
Testo completo
48
García, de la Concepción María Belén. "Novel Halogen(I) Reagents in the C-sp3- and Csp3-Bond Functionalization". Doctoral thesis, Universitat Rovira i Virgili, 2018. http://hdl.handle.net/10803/663299.
Testo completoAbstract (sommario):
En el treball presentat en aquesta tesi es mostren els desenvolupaments importants realitzats sobre l’ús de reactius d'halogen(I), específicament en la funcionalització d’enllaços C(sp2)-H i C(sp3)-H mitjançant reactius de iode(I) i brom(I).
El present manuscrit està dividit en tres apartats principals:
1-Reactius de iode(I) per la difuncionalització d’alquens.
2- Aminació oxidativa d'enllaços C-(sp3)-H de tetrahidrocarbazoles.
3-Aplicació de reactius de iode(I) o catàlisi de brom en la síntesi formal de (±)-aspidospermidina.
En la primera secció sobre la difuncionalització d'alquens, hem presentat la síntesi general, aïllament i caracterització de nous reactius de iode(I) amb fórmula R4N[I(O2CAr)2]. Aquests compostos posseeixen alta estabilitat davant l’exposició a l'aire i la humitat. El nostre interès radica en l'exploració de reaccions promogudes per iode electrofílic cap a una iodooxigenació de derivats d’estirè.
En la segona secció, s'ha dut a terme una exploració sobre l'ús del reactiu de Varvoglis PhI(NPhth)2. Aquest es va utilitzar per a la síntesi de reactius de iode(I) i brom(I) amb lligands de ftalimida. Com l’aminació de tetrahidrocarbazoles en la posició 4 no s’ha explorat fins al moment, desenvolupem una metodologia innovadora per dur a terme l’aminación oxidativa en C(sp3)-H de derivats de tetrahidrocarbazol, utilitzant reactiu de iode(I) o catàlisi de brom.
Finalment, en el tercer capítol volíem demostrar la versatilitat i el rendiment dels reactius d'halògens descrits en el capítol anterior per a la síntesi de (±)-aspidospermidina.El trabajo presentado en esta tesis representa algunos desarrollos importantes en reactivos de halógeno(I), concretamente hacia la funcionalización de los enlaces C(sp2)-H y C(sp3)-H a través de reactivos de yodo(I) y bromo(I). El presente manuscrito está dividido en tres partes principales: 1- Reactivos de yodo(I) para la difuncionalización del alquenos. 2- Aminación oxidativa de enlaces C-(sp3)-H de tetrahidrocarbazoles 3- Aplicación de reactivos de yodo(I) o catálisis de bromo hacía la síntesis formal de (±)-aspidospermidina. En la primera sección sobre la difuncionalización de alquenos, hemos presentado una síntesis general, aislamiento y caracterización de varios reactivos de yodo(I) con la fórmula R4N[I(O2CAr)2]. Estos compuestos poseen alta estabilidad ante el aire y la humedad. Nuestro interés radica en la exploración de reacciones promovidas por yodo electrófilo hacia la yodooxigenación con derivados de estireno. En la segunda sección, se ha llevado a cabo una exploración del uso del reactivo de Varvoglis PhI(NPhth)2. Este reactivo se usó para la síntesis de reactivos de yodo(I) y bromo(I) con ligandos de ftalimida. Como la aminación de tetrahidrocarbazolas en la posición 4 no se ha sido explorada hasta el momento, se. llevó a cabo el desarrollo de una metodología innovadora para dar lugar a una aminación oxidativa en C(sp3) con derivados de tetrahidrocarbazol, usando reactivo de yodo(I) o catálisis de bromo. Finalmente, en el tercer capítulo queríamos demostrar la versatilidad y el rendimiento de los reactivos de halógenos descritos en el capítulo anterior para dar lugar a la síntesis de un compuesto natural, tal como (±)-aspidospermidina.
The work presented in this thesis represents some major developments in halogen(I) reagents, specifically towards the functionalization of C(sp2)-H and C(sp3)-H bonds through iodine(I)- and bromine(I)-reagents. The present manuscript is divided into three principal parts: 1- Iodine(I) reagents for vicinal alkene difunctionalization 2- Oxidative amination of C-(sp3)-H bonds of tetrahydrocarbazoles 3- Application of iodine(I) reagent or bromine catalysis to the formal synthesis of (±)-aspidospermidine. In the first section on alkene difunctionalization, we have presented a general synthesis, isolation and characterization of several novel iodine(I) reagents with the formula R4N[I(O2CAr)2]. These compounds exhibit high air and moisture stability. We were interested in the exploration of reactions promoted by electro-philic iodine towards a vicinal iodooxy-genation of styrene derivatives. In the second section an exploration of the use of Varvoglis reagent PhI(NPhth)2 has been carried out. This reagent was used to the synthesis of iodine(I) and bromine(I) reagents with phthalimide ligands to stabilize the electrophilic halogen center. As oxidative amination of tetrahydrocarbazoles in position 4 has not been explored so far, we developed an innovative methodology to carryout the C(sp3) oxidative amination of tetrahydrocarbazole derivatives using iodi-ne(I) reagent or bromine catalysis. Finally, in the third chapter we wanted to demonstrate the versatility and performance of halogen reagents described in the previous chapter, which were used in the synthesis of (±)-aspidospermidine.
49
Renaudat, Alice. "Fonctionnalisation de liaisons C(sp3)-H non activées catalysées par le palladium". Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00704011.
Testo completoAbstract (sommario):
La fonctionnalisation de liaisons C-H réputées peu réactives ouvre de nouvelles perspectives en synthèse organique. Une stratégie efficace consiste en l'utilisation d'un métal de transition. Les travaux de thèse présentés dans ce mémoire s'inscrivent dans ce contexte. Dans un premier temps, la réaction étudiée, catalysée par le palladium, vise à étendre une méthodologie mise au point au laboratoire, permettant la synthèse de benzocyclobutènes par activation intramoléculaire de liaisons C(sp3)-H de groupements méthyles benzyliques, à des composés non aromatiques. Plusieurs substrats ont été synthétisés pour être ensuite placés dans les conditions de la réaction d'activation C(sp3)-H, dans le but d'induire la formation du cyclobutène ou du cyclobutane désiré. Le processus n'est pas sélectif et de nombreux produits secondaires sont obtenus par des réactions péricyliques ou par des réarrangements suite à l'ouverture du palladacycle intermédiaire. Dans un deuxième temps, nos travaux ont permis de mettre à jour une nouvelle réaction de fonctionnalisation C(sp3)-H, catalysée par le palladium permettant l'arylation d'esters en position β par un mécanisme original. Les investigations portent sur l'optimisation complète de cette réaction, la compréhension du mécanisme et le développement d'une version énantiosélective prometteuse. Le mécanisme de cette réaction, confirmé par des calculs DFT réalisés en collaboration avec C. Kefalidis et E. Clot, se rapproche formellement de celui observé en α-arylation, puisqu'il repose sur la formation d'un énolate de palladium. La stratégie mise au point permet le couplage, dans des conditions douces, d'esters simples et commerciaux avec des halogénures d'aryles contenant un groupement électronégatif en position ortho, donnant ainsi accès à des intermédiaires de synthèse intéressants tels qu'un analogue de la phénylalanine ou des composés fluorés.
50
Tuthill, Matthew Charles. "N-myc oncogene expression in neuroblastoma is dependent on Sp1 and Sp3". Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/987.
Testo completoAbstract (sommario):
Regulation of N-myc oncogene expression is an important determinant of the
biological behavior of neuroblastoma. The N-myc promoter contains several potential
binding sites for transcription factors of the Sp1 family. Mutation of a CT-box motif
contained within a 26 base pair region required for N-myc downregulation by retinoic
acid decreased basal transcriptional activity and altered DNA-protein interactions of the
promoter, while mutations flanking this motif did neither. On gel shift this region
generated 3 specific DNA-protein complexes that were reliant on wild type sequence of
the core CT element within it. Both Spl and Sp3 bound to the wild type probe as distinct
complexes in specifically retarded bands, while neither protein was present on mutated
sequences. Lysates from Drosophila S2 cells expressing exogenous Sp1 and Sp3
proteins were able to reproduce the gel shift complexes seen with neuroblastoma nuclear
extract. Transient transfections of S2 cells showed that individually or together, Sp1 and
Sp3 were able to trans-activate a N-myc CT-box-containing luciferase reporter construct
in a dose-dependent manner. Conversely, transfection of CT-box oligonucleotide was
able to decrease endogenous N-myc expression in neuroblastoma cells. Together these
results suggest that the CT-box element serves a critical functional role, and in the basal
state allows for N-myc transactivation by Spl and Sp3.