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1
Guo, Yixing. "Fluorescence Detection of Biological Thiols." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/586.
Testo completoAbstract (sommario):
Glutathione (GSH) is an important biological thiol, it performs significant biological functions such as serving an antioxidant which protect cells from oxidative stress by trapping free radicals which damage DNA and RNA. It is known that abnormal plasma levels of GSH have been linked to various human diseases. Therefore, the rapid, sensitive and highly selective detection of GSH is of great importance for investigating its functions in diseases diagnosis. Interestingly, we found in cetyl trimethylammonium bromide (CTAB) medium, the resorufin-based probe shows an extremely fast, highly selective response to GSH. The result indicates that this dye can be employed to detect GSH in biological samples such as human plasma. Cysteine (Cys) is another important biological thiol which is involved in a variety of significant cellur functions, including protein synthesis, detoxication, and metabolic process, etc. Abnormal levels of Cys are related to many diseases, such as slowed growth, Alzheimer's disease and cardiovascular disease. Thus, the detection and quantification of Cys in physiological media is of great importance. In this thesis, I am going to present two organic fluorescent probes (Resorufin-based probe and SNF probe) for the detection and quantification of Cys. In addition, we prove that they can directly quantify Cys in human plasma. The chemical mechanisms involved in the detection of Cys are discussed.
2
Fabrega, Prats Marta. "Low-molecular-weight thiols: identification of novel thiol compounds and applications in winemaking processes." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424804.
Testo completoAbstract (sommario):
Thiols are reduced sulphur molecules that occur both in plants and animals with relevant roles. The thiol group is strongly nucleophilic, thus participating in a lot of biological redox processes, as for example the modulation of oxidative stress and participation to enzymatic reactions.
Low-molecular-weight (LMW) thiols are a class of highly reactive compounds mainly involved in the maintenance of the redox homeostasis in the cells, thanks to the reactivity of their nucleophilic sulfur groups. In plants, they are implicated in the responses to almost all stress factors, as well as in the regulation of cell metabolism. Moreover, they can conjugate or make complexes with xenobiotics and toxic compounds (detoxification processes) and deactivate them, and they can post-translationally modify regulatory enzymes. They also have important implications in food quality and safety, as well as in human health. The most studied LMW thiols are glutathione and its biosynthetically related compounds (cysteine, gamma-glutamylcysteine and cysteinylglycine). Other LMW thiols are described in the literature, such as cysteamine, homocysteine, and many species-specific volatile thiols but less is known about them. Research shows that exists a huge amount of thiols in plants, but many species-specific and organ-specific thiols remain to be identified. Some of these unknown LMW thiols have light dependence, suggesting that they could be related to the photosynthesis processes.
Recent advances in technology should help in this challenging work, helping to know the physiological and metabolic function in plants. However, their identification remains challenging due to their low concentration in plant tissues.
In order to discover new unidentified thiols, in this work it was carried out a derivatization with SBD-F (ammonium 7-fluoro 2,1,3-benzooxadiazole-4-sulfonate) of the plant extracts, and then, SBD-derivatives were analyzed by HPLC-fluorescence and LC-MS/MS in negative mode using an ion trap (Varian 500 MS), to obtain their fragmentation pattern. Known LMW thiols such as cysteine, homocysteine, glutathione, cysteamine, gamma-glutamylcysteine, N-acetylcysteine and cysteinylglycine were used as reference compounds and their fragmentation pattern was first studied in order to highlight a fragmentation rule and molecular markers to systematically identify the unknown LMW thiols. Also high resolution measurements were obtained on a Xevo G-2 Q-TOF mass spectrometer (Waters).
After the derivatization with the fluorophore, thiols can be easily recognized in fragmentation spectra due to the presence of a clear signal arising from the SBD-S fragment (m/z 231). This fragment corresponds to the fluorophore attached to the sulphur group from the LMW thiol. This signal was then used as a marker to confirm the presence of thiol groups in unknown molecules. In this way, some molecules could be identified and further confirmed by Q-TOF analysis; as for example the presence of thioglucose and glutathione containing derivatives. This protocol now opens the way to the identification of unknown thiol molecules.
In winemaking processes, LMW thiols and specifically GSH, have an antioxidant function, which is present in grapes, must and wine. They help contrasting the oxidative browning by protecting grapes, and also the must during fermentation and the wine during the aging processes. They have a key role in the antioxidant activity by protecting wines, mostly white ones, from the oxidative process during aging. Due to this fact, in this study it was also tried to develop and optimize an easy and fast method to quantify the amount of LMW thiols in several German grape varieties (white and red). These compounds were extracted and analyzed using the fluorescent dye SBD-F and HPLC-FL separation. Also using HPLC, the sugars and organic acids were also quantified.
The results of this quantification show that there is a very good reproducibility either in sampling or in the measurement of these compounds in the grape berries. This method can be also applied in must, wine and yeast. The method allowed not only the quantification of GSH, but also of its related compounds: cysteine, gamma-glutamylcysteine and cysteinylglycine in the same chromatogram, showing also the correlation between them. This study on German grape varieties is then showing that GSH is the most important LMW thiol in grapes, whose content is largely depending on the variety. Given their role as an antioxidant and possible beneficial effects during the winemaking processes, GSH and related LMW thiols are an important factor to consider in the evaluation of the grapes used for making wine.<br>I tioli sono composti ridotti dello zolfo che svolgono importanti funzioni in animali e piante. Il gruppo -SH è fortemente nucleofilo, per tale motivo queste molecole sono spesso coinvolte in processi biologici di ossidoriduzione, come ad esempio la modulazione degli stress ossidativi e la partecipazione a varie reazioni enzimatiche.
I tioli a basso peso molecolare (LMW) sono una classe di composti coinvolti principalmente nel mantenimento dell’omeostasi ossidoriduttiva nella cellula, tale caratteristica si deve alla reattività dei loro gruppi tiolici nucleofili. Nelle piante sono coinvolti nella risposta a quasi tutti i fattori di stress e nella regolazione del metabolismo cellulare. I tioli LMW possono legarsi o creare complessi con composti tossici disattivandoli (detossificazione), inoltre possono modificare, dopo la traduzione, enzimi regolatori. Queste molecole sono implicate nella qualità e salubrità degli alimenti e anche nella salute umana.
I tioli LMW più studiati sono il glutatione e i suoi composti derivati (cisteina, gamma-glutamil-cisteina e cisteinil-glicina). In letteratura sonostati descritti altri tioli LMW come la cisteammina, l’omocisteina e molti altri tioli volatili specie-specifici di cui però poco è conosciuto. In particolare, nelle piante è dimostrata la presenza di moltissimi tioli specie-specifici e organo-specifici molti dei quali però non sono ancora stati identificati. Alcuni di questi tioli LMW sconosciuti sono luce-dipendenti e ciò suggerisce un loro coinvolgimento nel processo della fotosintesi.
I miglioramenti nella tecnologia potrebbero aiutare lo studio e la conoscenza della funzione fisiologica e metabolica di questi composti. Tuttavia la loro identificazione è resa ardua dalla loro bassa concentrazione nei tessuti vegetali.
In questo lavoro, allo scopo di scoprire nuovi tioli non ancora identificati, sono stati derivatizati con SBD-F degli estratti di piante e in seguito i derivatizzati sono stati sottoposti ad analisi HPLC a fluorescenza e LC-MS/MS in modalità negativa usando una trappola ionica (Varian 500 MS) per ottenere la frammentazione. Sono stati usati come riferimento i tioli LMW già noti come la cisteina, l’omocisteina, il glutatione, la cisteammina, la gamma-glutamil-cisteina, l’N-acetilcisteina e la cisteinil-glicina, i cui modelli di frammentazione sono stati inizialmente studiati per evidenziare la modalità di frammentazione e i marcatori molecolari che hanno consentito la identificazione sistematica di tioli LMW sconosciuti. Inoltre è stata ottenuta la misurazione ad alta risoluzione su spettrometro di massa Q-ToF (Waters) su Xevo G-2.
Dopo la derivatizzazione con fluoroforo i tioli possono essere facilmente riconosciuti dallo spettro di frammentazione per la presenza di un chiaro segnale dato dal frammento SBD-S (m/z 231). Questo frammento corrisponde al fluoroforo legato al gruppo tiolico, ed è stato usato per marcare e confermare la presenza del gruppo tiolico nelle molecole sconosciute. In questo modo le molecole possono essere identificatee poi confermate dall’analisi Q-ToF come nel caso del tioglucosio e di derivati contenenti glutatione. Il protocollo che è stato definito con il presente lavoro permette ora l’identificazione di nuovi composti dello zolfo al momento sconosciuti.
Nel processo di produzione del vino, i tioli LMW e il glutatione in particolare, hanno una importante funzione antiossidante che si manifesta nell’uva, nel mosto e nel vino. I tioli contribuiscono a contrastare l’imbrunimento ossidativo delle proteine nell’uva e soprattutto nel mosto durante la fermentazione e del vino nei diversi processi di lavorazione. I tioli giocano perciò un ruolo chiave nella conservazione del vino con la loro attività antiossidante, in particolar modo nei vini bianchi. Per questa ragione è stato condotto uno studio volto a sviluppare una metodologia semplice e rapida per la quantificazione dei tioli LWM totali. In tale studio sono state poste a confronto diverse varietà tedesche di uva da vino. I composti dello zolfo sono stati estratti ed analizzati utilizzando un colorante fluorescente SBD-F e separazione HPLC-FL. Sono stati quantificati anche gli zuccheri e gli acidi organici tramite HPLC.
I risultati di questa quantificazione mostrano un’elevata riproducibilità tra i campioni e tra le misurazioni di questi composti nelle bacche. Il metodo è utilizzabile anche su mosto, vino e lieviti. Il metodo permette non solo la quantificazione del glutatione ma anche di altri composti relativi nello stesso cromatogramma e mostra una correlazione tra di essi. Il confronto di varietà differenti mostra la presenza di GSH nella maggior parte dei tioli dell’uva, mentre il loro contenuto è molto influenzato dalla varietà. In considerazione del loro ruolo di antiossidanti, il GSH e i tioli LMW possono avere un ruolo favorevole nella vinificazione e sono perciò un fattore fondamentale che deve essere preso in considerazione nelle decisioni che riguardano il processo di produzione del vino.
3
Kleinhenz, Joseph Patrick. "Medium and higher molecular weight volatile thiols in aged cheddar cheese and their relation to flavor." Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054657696.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2003.<br>Title from first page of PDF file. Document formatted into pages; contains xix, 181 p.; also includes graphics (some col.). Includes bibliographical references (p. 158-168). Available online via OhioLINK's ETD Center
4
Nasri, Issad. "Synthèse et activité antifongique de thiols polyfonctionnels et dérivés apparentes : relation structure chimique-activité antiadhérente." Nancy 1, 1991. http://www.theses.fr/1991NAN10459.
Testo completo
5
Emonet, Piccardi Nathalie. "Place des thiols dans la photoprotection." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10246.
Testo completoAbstract (sommario):
L'irradiation ultraviolette a (uva : 320-400 nm) exerce un role potentiel dans la carcinogenese cutanee, ainsi que dans l'heliodermie, par des mecanismes impliquant les especes reactives de l'oxygene. La mise au point d'une protection efficace contre ce type de radiations devient donc une necessite en termes de sante publique. L'utilisation des topiques solaires actuels ne permet pas de garantir une protection optimale contre les uva. En dernier ressort, la protection des cellules cutanees, exposees aux uva, repose sur les systemes de la defense antiradicalaires, dont les thiols. Par une approche originale, nous avons montre les limites des photoprotecteurs externes en termes de prevention des degats genomiques et d'epargne des systemes antioxydants intracellulaires, definissant ainsi l'adn et le glutathion comme des biomarqueurs potentiels de l'efficacite reelle apportee par les topiques solaires. Par ailleurs, ce travail montre l'interet d'un apport exogene de thiols et/ou d'oligo-elements (selenium et zinc) en termes de photoprotection. La modulation redox de la synthese des proteines de stress sous uva a egalement ete apprehendee. Cette etude conduit a associer photoprotection externe et interne, dans un nouvel axe de recherche permettant la mise au point d'une photoprotection parfaite, s'opposant aux effets immediats et a longs termes de l'exposition solaire.
6
Kasprzak, Scott Edward. "Small-scale polymer structures enabled by thiol-ene copolymer systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28109.
Testo completoAbstract (sommario):
Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.<br>Committee Chair: Gall, Ken; Committee Member: Graham, Samuel; Committee Member: Jacob, Karl; Committee Member: Perry, Joe; Committee Member: Pierron, Olivier.
7
Nekrassova, Olga. "Thiols specification and detection strategies via electroanalysis." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409118.
Testo completo
8
Ellwood, Josephine Anne. "Raman band intensities of thioethers and thiols." Thesis, Royal Holloway, University of London, 1989. http://repository.royalholloway.ac.uk/items/c5538f6e-c19e-4780-a724-6bae6abecc72/1/.
Testo completoAbstract (sommario):
Raman spectroscopy is potentially a useful technique for the analysis of thioethers and thiols because of the characteristic set of bands which appears in the C-S stretching region. A review of previous studies on Raman band intensity measurements is presented in which the experimental difficulties and influencing factors are given. An experimental system has been developed around a Coderg PHO Raman spectrometer for the measurement of absolute Raman band intensities. This includes the novel use of a Pockels cell for the accurate determination of depolarisation ratios. Carbon tetrachloride has been assessed as a suitable internal standard for use with this system. Raman band intensities are given for five thioethers and two thiols. Several bands are identified as being characteristic of sulphur-containing hydrocarbons. Analysis of bands in the C-S stretching region is accomplished by considering the intensity contributions provided by individual groups in the molecule, resulting in a successful prediction of the C-S stretching band intensities for t-butane thiol. In addition, temperature studies have been conducted for ethyl methyl sulphide in order to attempt calculation of the energy barrier between the two conformations. A computer programme has been developed for the theoretical calculation of Raman band frequencies and intensities. Molecular parameters have been derived for dimethyl sulphide, including an ab initio force field. Tests for transferabilityof these data to ethyl methyl sulphide and deuterated dimethyl sulphide have produced encouraging results. A study of infra-red intensities of thioethers has been carried out. This is an extension of some previous work in which the necessity to resolve individual bands is eliminated. For several discrete spectral regions quantification is made of the effects of a sulphur atom on C-H band intensities, thus allowing successful intensity predictions for other molecules studied. Suggestions for further work in this field are given.
9
Kading, Tristan James. "Distribution of thiols in the northwest Atlantic Ocean." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79298.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Joint Program in Chemical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 30-38).<br>Thiol substances can form stable complexes with metals (especially copper and mercury) in the surface ocean that can impact cycling and bioavailability of those elements. In this study, I present seven concentration profiles of cysteine and glutathione, two low-molecular weight thiols, from the coastal northwest Atlantic Ocean and the Bermuda Atlantic Time Series (BATS) sampling site in the Sargasso Sea, a first for these regions. These two thiols were found in the upper 200 meters of the ocean at all sites, and the total thiol concentration varied from 0.2 to 3.2 nM. The highest concentration of both thiols was found at the deep chlorophyll maximum in most samples. Thiol concentrations were higher on the continental shelf than in the open ocean. The observed distribution of cysteine and glutathione and thermodynamic stability of copper complexes suggests that Cu(I)-dithiol complexes may be the dominant surface ocean copper and thiol species. Mercury-thiol complexes were also present in thermodynamically modeled seawater, which may provide a vector for mercury uptake in the surface ocean.<br>by Tristan Kading.<br>Ph.D.
10
Abbas, Ewadh Mufeed-J. A. "The involvement of thiols in endothelial cell toxicity." Thesis, Cardiff University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316383.
Testo completo
11
Silvester, Stephen. "The copper-catalyzed oxidation of biologically relevant thiols." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265370.
Testo completo
12
Zhu, Tianxia. "Detection of Thiols by o-Quinone Electrocatalytic Sensors." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1340981269.
Testo completo
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Dos, Santos Noëmie. "Contrôle de la sélectivité des réactions d'hydrodésulfuration et d'hydrogénation en hydrotraitement : étude cinétique sur des essences craquées modèles." Lyon 1, 2008. http://tel.archives-ouvertes.fr/docs/00/36/01/95/PDF/these-NDS-vf.pdf.
Testo completoAbstract (sommario):
Dans le contexte pétrolier d'une future mise sur le marché d'essences "zéro soufre", ce travail se propose de revisiter la problématique de l'hydrodésulfuration sélective des essences de FCC sur catalyseur CoMo/Al2O3, procédé ayant pour but de désulfurer au maximum cette coupe pétro-lière tout en minimisant l'hydrogénation des oléfines. Pour mieux comprendre les mécanismes réactionnels mis en jeu ainsi que de tenter de préciser le nombre de type de sites actifs présents sur le catalyseur, une approche expérimentale à l'aide de molécules modèles a été choisie afin d'étudier la cinétique des réactions d'HDS, d'HYD, d'isomérisation et de recombinaison des oléfines avec l'H2S. Ce travail a permis de confirmer l'existence d'un équilibre thermodynami-que entre les oléfines et les mercaptans ainsi qu'une adsorption compétitive des oléfines et des composés soufrés sur les mêmes sites actifs du catalyseur. Nous avons pu montrer que l'hydro-gène sulfuré gouverne à lui seul la sélectivité HDS/HYD, et ce quel que soit l'ajout de compo-sés annexes (composés azotés, xylènes, hydrogène. . . ) dans le milieu réactionnel. Un modèle cinétique basé sur l'existence d'un seul type de sites actifs a permis d'expliquer une grande par-tie des résultats obtenus au cours de ce travail<br>In the oil context of a future market of gasoline without sulphur, this work deals with the selec-tive hydrodesulphurization of FCC gasoline on a CoMo/Al2O3 catalyst, the aim of this process beeing to remove the maximum of sulphur compounds while minimizing the olefins hydro-genation. For a better understanding of the mechanisms involved in this process and to try to clarify the number of different active sites on the catalyst, an experimental approach with model compounds has been chosen to study the kinetics of the HDS, HYD, isomerisation and recombination reactions. This work allowed us to evidence the existence of a thermodynamic equilibrium between olefins and thiols, and adsorption of olefins and sulphur compounds has been demonstrated to occur on the same active sites. Moreover, our results indicate that the hydrogen sulphide governs the selectivity HDS/HYD, whatever was the addition of secondary compounds (nitrogen compounds, xylenes, hydrogen…). A kinetic model based on the exis-tence of a single type of active sites allowed to explain most of the results obtained during this work
14
Greno, Béatrice. "Optimisation d'une méthode de synthèse photochimique de thiols primaires à partir d'oléfines terminales." Pau, 1997. http://www.theses.fr/1997PAUU3013.
Testo completoAbstract (sommario):
Les travaux présentés concernent l'étude de la photosulfhydratation, procédé industriel connu pour produire des thiols primaires à partir d'oléfines terminales. Cette synthèse photochimique s'accompagne de la formation de produits soufrés secondaires dont l'élimination occasionne un surcoût de production important. Les objectifs de notre étude se sont donc inscrits dans le cadre de ce contexte industriel et se situent à deux niveaux : mieux comprendre les aspects fondamentaux de la réaction de photoaddition du sulfure d'hydrogène sur le 1-octene, en régime dynamique, et apporter des solutions pour améliorer la sélectivité en thiol primaire. Le premier objectif a été réalisé au niveau de l'étude de la réaction de photosulfhydratation sous pression atmosphérique en milieu benzénique et éthéré (diglyme). Des différences entre ces deux milieux ont été mises en évidence sur le plan quantitatif et au niveau des sélectivités. L'influence des phosphites organiques alkyles sur la vitesse et le terme des réactions a été étudiée : l'addition de phosphite, si elle accélère la vitesse de disparition de l'oléfine, n'améliore pas la sélectivité en thiol primaire mais plutôt celle en sulfure. En l'absence de données expérimentales, une étude théorique a été engagée dans le but d'élaborer un mécanisme plausible pour la réaction de photosulfhydratation dans le benzène et dans le diglyme. La méthode semi empirique AM1 (Austin Model 1) a permis d'évaluer la probabilité d'intervention de voies réactives à priori possibles dans le mécanisme et d'apprécier leur degré de réversibilité. Il en ressort la proposition d'un mécanisme unique à l'exception des phases d'initiations différentes d'un solvant à l'autre. Le modèle cinétique proposé rend correctement compte des courbes expérimentales : l'intervention de phénomènes de diffusion non équivalents d'un solvant à l'autre a été retenu, ceci en accord avec le fait que certains des processus du mécanisme considéré sont des processus sans énergie d'activation. Le second objectif tendant à améliorer la sélectivité en thiol primaire concerne l'étude de la réaction de photosulfhydratation en milieu h#2s condensé. Cette étude a nécessité la mise au point et l'exploitation d'un micropilote pressurisé. Deux voies réactives ont été examinées : la réaction par photolyse directe de h#2s et la réaction photoamorcée en présence de benzophénone. Ces deux voies conduisent à d'excellents rendements en thiol primaire. La voie par photoamorçage a permis d'obtenir sous certaines conditions de meilleurs résultats du point de vue des rendements et de la sélectivité en thiol primaire.
15
Bekendam, Roelof. "Vascular thiol isomerases : targeting and regulation." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0219.
Testo completoAbstract (sommario):
La protéine disulfure isomérase (PDI) est une protéine de 57 kDa résidant principalement dans le réticulum endoplasmique (ER) où elle est impliquée dans le repliement approprié des protéines nouvellement synthétisées. PDI peut être sécrétée par les plaquettes et les cellules endothéliales pour participer à la formation du thrombus. Cependant, le mécanisme exact par lequel PDI module et régule les substrats est insaisissable. Dans la première partie de cette thèse, une classe des inhibiteurs est identifiée par un criblage à haut débit. Ces inhibiteurs, appelés bepristats, sont avérés inhiber sélectivement le PDI dans la famille des thiols isomérases. L'interférence avec la fixation du substrat permet aux bepristats d'inhiber l'agrégation plaquettaire sans affecter la sécrétion plaquettaire. Les bepristats déplacent le linker X du site de liaison hydrophobe et augmentent l'activité des cysteines catalytiques. Globalement, ces résultats démontrent un mécanisme par lequel la ligature du substrat du site de liaison hydrophobe augmente l'activité catalytique. Dans la deuxième partie de la thèse, la régulation de la PDI dans le système vasculaire a été examinée plus avant. PDI est connu pour interagir avec l'oxyde nitrique par S-nitrosylation. L'activité de la thiol isomérase sur la surface cellulaire des cellules endothéliales peut être inhibée par le NO exogène et la régulation positive endogène de l'eNOS. PDI S-nitrosylé inhibait l'agrégation plaquettaire, la sécrétion et la formation du thrombus. En conclusion, la S-nitrosylation des thiol isomérases représente un mécanisme par lequel le PDI maintient la quiescence dans le système vasculaire<br>Protein disulfide isomerase (PDI) is a 57 kDa protein mainly residing in the endoplasmic reticulum (ER) where it is involved in the proper folding of newly synthesized proteins. PDI can be secreted by both platelets and endothelial cells to participate in thrombus formation. However, the exact mechanism by which PDI modulates and regulates substrates remains elusive. In the first part of this thesis a class of compounds is identified through high throughput screening. These compounds, termed bepristats, were shown to selectively inhibit PDI within the thiol isomerase family. Interference with substrate binding allows bepristats to inhibit platelet aggregation without affecting platelet secretion. Further biochemical analysis revealed that bepristats displace the x-linker from the hydrophobic binding site and paradoxically increase the activity of catalytic cysteines within the a and a’ domains. Overall, these results demonstrate a mechanism by which substrate ligation of the hydrophobic binding site increases the catalytic activity of thioredoxin-like motif containing domains. In the second part of the thesis the regulation of PDI within the vasculature was further examined. PDI is known to interact with nitric oxide through S-nitrosylation. Nitric oxide is a potent inhibitor of the vasculature. Thiol isomerase activity on the cell surface of endothelial cells can be inhibited by both exogenous NO and endogenous upregulation of eNOS. S-nitrosylated PDI was subsequently shown to inhibit platelet aggregation, secretion and thrombus formation. Concluding, S-nitrosylation of thiol isomerases represents a mechanism by which PDI maintains quiescence within the vasculature
16
Le, Neindre Morgane. "Polymères linéaires et branchés fonctionnels par synthèse radicalaire et thiochimie." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066408/document.
Testo completoAbstract (sommario):
La chimie des thiols est un outil puissant et polyvalent pour la préparation de polymères et de matériaux fonctionnels. La fonction thiol est cependant incompatible avec la polymérisation radicalaire. Au cours de cette thèse, l'évaluation de fonctions thiocarbonyl et thioester en tant que groupements protecteurs de thiols lors de polymérisations radicalaires contrôlées a montré que le groupement xanthate, ou dithiocarbonate, est un excellent groupement protecteur. Des copolymères polythiol linéaires bien définis ont ainsi pu être synthétisés à partir d'un monomère méthacrylate portant une fonction xanthate. Les polythiols pouvant conduire à des réactions de réticulation via la formation de ponts disulfure, des séquences monotopes de déprotection par aminolyse et fonctionnalisation des polythiols via différentes réactions thiol-X ont ensuite été mises au point. Les monomères fonctionnels xanthate ont ensuite été mis à profit pour synthétiser des polymères branchés. L'aminolyse d'une partie des xanthates avant la polymérisation permet en effet d'obtenir des monomères thiol et ainsi d'introduire du transfert aux thiols lors de la polymérisation. Les polymères branchés fonctionnels obtenus présentent des viscosités plus faibles, ainsi qu'une structure plus compacte, que leurs analogues linéaires<br>Thiol chemistry is a versatile and powerful tool for the preparation of functional polymers and materials. However, thiols are incompatible with radical polymerization. In this thesis, thiocarbonyl and thioester moieties were evaluated as thiol protecting groups for controlled radical polymerizations. The xanthate, or dithiocarbonate, moiety proved to be the best all-around protecting group, and well-defined polythiol copolymers were prepared from a methacrylate monomer carrying a xanthate moiety. As polythiol are prone to gel formation due to the formation of disulfide bridges, one-pot deprotection and functionalization were carried out via aminolysis and subsequent functionalization with different thiol-X reactions. The functional monomer carrying a xanthate group was then used to prepare branched polymers. Partial aminolysis of the xanthate moieties leads to monomers carrying a thiol group, which introduced transfer to thiol during the polymerization. The functional branched polymers obtained have lower viscosities and a more compact structure than their linear analogues
17
Chen, Hui-Chuen. "The urinary excretion of mercapturic acids in free-living adult males." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12052009-020010/.
Testo completo
18
Hurd, T. R. "Interactions between mitochondrial protein thiols and reactive oxygen species." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604824.
Testo completoAbstract (sommario):
This work investigates the reactions of proteins with ROS when mitochondria are exposed to H<sub>2</sub>O<sub>2</sub> or when they generate ROS endogenously. Using isolated mitochondria, those proteins that are particularly sensitive to low concentrations of H<sub>2</sub>O<sub>2</sub> and to ROS generated by the mitochondrial electron transport chain were first identified using a method called Redox-Difference Gel Electrophoresis (Redox-DIGE). Most redox sensitive thiol proteins identified by Redox-DIGE were involved either in fatty acid oxidation or in the regulation of the pyruvate dehydrogenase complex. Next the mechanisms by which ROS selectively oxidise mitochondrial thiol proteins were investigated; it was determined that H<sub>2</sub>O<sub>2</sub> generated by the electron transport chain may either oxidise mitochondrial thiol proteins directly or indirectly, through oxidation of the peroxiredoxin and thioredoxin redox couples. To determine if ROS generated by mitochondria might act as a redox signal by altering the functions of mitochondrial proteins, the effect of protein thiol oxidation was tested on the activity of two proteins: pyruvate dehydrogenase kinase and propionyl-CoA carboxylase. Loss of pyruvate dehydrogenase kinase and propionyl-CoA carboxylase activity correlated with protein thiol oxidation and was very sensitive to ROS, suggesting a plausible mechanism of redox regulation of these proteins <i>in vivo. </i>Lastly, glutathionylation of complex I was investigated in intact mitochondria exposed to a glutathione oxidant; two cysteine residues on the 75 kDa subunit of complex I were shown to become glutathionylated. The functional effect of glutathionylation of these two cysteine residues on complex I activity is currently under investigation.
19
Gracheva, Svetlana. "Development of novel techniques for monitoring anti-oxidant thiols." Thesis, Nottingham Trent University, 2009. http://irep.ntu.ac.uk/id/eprint/182/.
Testo completoAbstract (sommario):
The clinical exploitation of physiological biomarkers could yield considerableimprovements in diagnosis and treatment providing their measurement can be conducted peedily and preferably at the point of care. The project has sought to investigate the development of new methods that could allow such measurements to be made. The various biomarkers that could be exploited as the basis of a general “index” of physiological wellbeing have been identified and their potential clinical merit critically appraised. Anti-oxidant sulphur compounds (cysteine, glutathione, sulphite) were selected as potential targets on the basis of their physiological role in protecting the body from damage by free radicals. The variation in their concentration within biofluids is widely acknowledged as a useful diagnostic gauge as to the degree of oxidative stress that an individual may be experiencing. The main problem, from a clinical perspective, is the lack of a suitable procedure for monitoring their concentration speedily at, or by, the patient. A brief assessment of the various electroanalytical options (encompassing voltammetric, amperometric and potentiometric methodologies) available for the detection of the sulphur anti-oxidants has been conducted. A potentiometric detection strategy was found to offer numerous advantages and a novel indicator family based on quinone interaction adopted and forms the foundation of the work presented herein. The reaction mechanism has been elucidated and the analytical applicability of the system investigated using a variety of techniques – covering both chromatographic, spectroscopic and electrochemical methodologies. The system has been characterised in terms of selectivity, sensitivity and its efficacy for the quantification of thiol containing pharmaceuticals and various biofluids (urine and plasma) has been demonstrated. The simplicity of the detection methodology is shown to markedly contrast alternative thiol detection strategies. The transfer of the technology to a mass production format through the adoption of screen print electrode formats has been achieved. A series of clinical trials were performed and the efficacy of the approach and the underlying technology format demonstrated. The results have been corroborated using standard techniques and the routes through which the system can be adopted within mainstream biomedical environments highlighted. An alternative sensor system based on a composite polymer laminate approach was also investigated as a route through which prototype sensors could be speedily prepared and which would be more accessible to general chemistry laboratories. A new approach to the detection of sulphite – based on the quinone system – was used as the principal detection system to allow the system to be evaluated and proof of principle demonstrated. The fabrication methodology adopted has been found to provide a highly versatile option for the construction of polymer film electrodes.
20
Maclellan, Paul William. "Asymmetric synthesis of tertiary thiols by lithiation of thiocarbamates." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/asymmetric-synthesis-of-tertiary-thiols-by-lithiation-of-thiocarbamates(ee91a5d1-63ba-458b-87bc-fd32e7c27b96).html.
Testo completoAbstract (sommario):
Tertiary thiols are a synthetically challenging class of compounds to prepare asymmetrically. The few reported methods for preparing these species require restrictive functionality to be incorporated into the products or are limited to employing simple carbon electrophiles. This thesis details investigations into the lithiation of N-aryl thiocarbamates. A stereoselective intramolecular arylation within lithiated thiocarbamates has been developed allowing the construction of quaternary stereocentres next to sulfur. Simple deprotection allows the isolation of enantiomerically pure tertiary thiols. A procedure for aryl migration within benzylic thiocarbamates has been developed and optimised. Rearrangement occurs in good yield and excellent stereoselectivity in a wide range of thiocarbamate substrates. Various substitution patterns are tolerated on the migrating aryl ring, the benzylic aryl ring and on the benzylic carbon centre. Extension of this methodology has incorporated an asymmetric alkylation of achiral benzylic thiocarbamates as a method of preparing aryl migration substrates. This allows the asymmetric synthesis of tertiary thiols in 2 steps from simple achiral precursors. Aryl migration has also been found to occur in lithiated allylic thiocarbamates with high stereospecificity, allowing preparation of a wider range of tertiary thiols.
21
Winski, Shannon Lee 1967. "Interactions of pentavalent and trivalent arsenic with intracellular thiols." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/278054.
Testo completoAbstract (sommario):
Trivalent arsenic (As(III)) exposure is linked to cancer, but exposure includes pentavalent arsenic (As(V)). These forms interconvert in biological systems, and the mechanism is not understood. Arsenic has a high affinity for sulfhydryls, and the interaction of As(III) and As(V) with biological sulfhydryls and cellular uptake was investigated in this study. Incubation of rat blood at 1 mM arsenic showed As(V) uptake, membrane and protein binding to be time dependant. These processes were almost immediate with As(III) incubation. Incubation at 25 mM As(V) resulted in 40% thiol depletion with no oxidized glutathione formation. Metabolite analysis showed half of the As(V) converted to As(III). In As(III) incubation, 27% thiol depletion occurred with 300% increase in GSSG. As(V) reduction combined with thiol depletion could indicate that arsenate used sulfhydryls as reducing equivalents. Because arsenate uptake was slow this reduction may not be a main contributor to the overall in vivo process.
22
Al-farawati, Radwan. "Thiols, sulfide, and speciation with trace metals in seawater : electroanalytical studies and speciation modelling of thiols and sulfide with trace metals in seawater." Thesis, University of Liverpool, 1997. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243218.
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23
Petit, Emilie. "Réactivité de polyphénols du vin sous conditions oxydantes : hémisynthèse des mongolicaïnes, et d’adduits entre polyphénols et thiols odorants." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14915/document.
Testo completoAbstract (sommario):
Le vin est un milieu complexe qui évolue tout au long des étapes devinification. Pour mieux appréhender ses qualités et ses défauts, de nombreuses équipesde recherche s’intéressent à la compréhension de la chimie du vin. Dans ce contexte, lesujet de ce mémoire concerne l’étude de l’évolution chimique de certaines moléculespolyphénoliques du vin sous conditions oxydantes et/ou acides, afin d’isoler et decaractériser de nouveaux composés susceptibles de se former dans le vin. Deux aspectssont examinés. Le premier concerne l’oxydation de deux flavano‐ellagitannins, lesacutissimines A et B, formées à partir d’un monomère de tannins condensés, lacatéchine, et d’un ellagitannin C‐glucosidique, la vescalagine, extraite du bois de chênepar le vin lors de l’élevage en barrique. Cette étude a permis d’isoler les mongolicaïnes Aet B et deux analogues du camelliatannin G et de mettre en évidence leur formation parun mécanisme d’autoxydation. Le deuxième aspect concerne l’évaluation desconséquences de la présence de certains polyphénols dans le vin sur les composésthiolés odorants. Leur comportement et leur réactivité chimiques sont décrits dans desmilieux différents, avec l’hémisynthèse de thio‐ellagitannins sous conditions acides, et laformation d’adduits thio‐catéchols et thio‐pyrogallols sous conditions oxydantes,transformations chimiques pouvant occasionner la perte des odeurs et arômes du vindus aux composés thiolés odorants<br>The wine is a complex medium that evolves throughout the different stages ofthe wine making process. To understand both the qualities and defects of wine,numerous research team worldwide investigate the chemistry of wine. In this context,the subject of this thesis concerns the study of the chemical evolution of some winepolyphenolic molecules under oxidizing and/or acidic conditions in the aim of isolatingand characterizing new compounds likely formed in wine. Two aspects are examined.The first one is the study of the oxidation of two flavano‐ellagitannins, acutissimins Aand B, formed from a monomer of condensed tannins, catechin, and a C‐glucosidicellagitannin, vescalagin, extracted from oak wood by the wine solution during its agingin barrels. This study led to the isolation of mongolicains A and B and two analogues ofcamelliatannin G, and revealed their formation according to an autoxydationmechanism. The second aspect of this work concerns the consequences of the presencein wine of some polyphenols on wine odorous thiols. Their chemical behavior andreactivity are described in different media, with the hemisynthesis of thio‐ellagitanninsunder acidic conditions, and the formation of thio‐catechol and thio‐pyrogallol adductsunder oxidizing conditions, chemical transformations that could explain the loss ofodors and aromas due to wine odorous thiols
24
Mukiza, Janvier. "Rhenium complexes with pontentially multidentate ligands containing the amino, imino, hydroxy and thiol groups." Thesis, Nelson Mandela Metropolitan University, 2016. http://hdl.handle.net/10948/12308.
Testo completoAbstract (sommario):
The chemistry of rhenium has received considerable interest due to its versatility in various catalytic applications, fixation and especially the potential use of 186Re and 188Re radionuclides in nuclear medicine. This study investigates the synthesis and characterisation of rhenium complexes with potentially multidentate ligands containing the amino, imino, hydroxyl and thiol groups. It reports new rhenium complexes in the +1, +3, +4 and +5 oxidation states, which display structural diversity, from monomers to ligand-bridged dimers as well as metal-metal multiply bonded dimers. The reaction of orotic acid (H2oa) and 2-mercapto-orotic acid (H2moa) with trans- [ReOX3(PPh3)2] (X = Cl, Br) were studied and led to the formation of ligand-bridged dimers with metal-metal multiple bonds i.e. (μ-Br)(μ-O)(μ-oa)[Re2 IVBr(OEt)2(PPh3)2], (μ-X)(μ-O)(μ-oa)[Re2 IVX2(OiPr)(PPh3)2] and (μ-Cl)(μ-O)(μ-moa)2[Re(PPh3)]2. The reaction of H2oa with [ReO2(py)4]Cl, [Re(dab)Br3(PPh3)2] (H2dab = 1,2- diaminobenzene) and [Re(CO)5Cl] were also studied and monomeric complexes [ReO(py)2(OEt)(oa)], [Re(dab)Br(oa)(PPh3)2] and (Ph4P)[Re(CO)3(H2O)(oa)] were isolated. The treatment of 5-amino-orotic acid (H2aoa) with [ReOBr3(PPh3)2] led to dimers with metal-metal triple bonds ReIV≡ReIV i.e. (μ-Br)(μ-O)(μ-oa)[Re2 IVBr(OEt)2(PPh3)2], (μ-Br)(μ-O)(μ-oa)[Re2 IVBr2(OiPr)(PPh3)2], as well as the monomer [ReV(apd)Br(aoa)(PPh3)2] (apd2− = 5-imidopyrimidine-2,4-dione). The chelating ligand 5-aminopyrimidine-2,4-dione (H2apd) was formed by oxorhenium(V)-catalysed decarboxylation of 5-amino-orotic acid (H2aoa) (see Scheme 1). The reaction of the Schiff base derivative of 5-amino-ortic acid, salicylimine-orotic acid (H2soa), with trans-[ReOI2(OEt)(PPh3)2] in ethanol was also investigated and led to the formation of the rhenium(III) complex salt [Re(coa)I(PPh3)2]I [Hcoa = 5-(2- hydroxybenzylideneamino)pyrimidine-2,4(1H,3H)-dione]. The chelating Hcoa is also formed from the oxorhenium(V)-catalysed decarboxylation of H2soa and coordinates to the rhenium(III) ion as a monoanionic tridentate N,O,O-donor chelate via the phenolate and ketonic oxygens, and the imino nitrogen atom. However, decarboxylation of H2soa was not observed in its reaction with [ReOCl3(PPh3)2], which led to the isolation of [ReOCl(soa)(PPh3)]. The reaction of the carboxamide derivative of 5-aminoorotic acid, 5-(5-aminopyrimidine-2,4(1H,3H)- dioxamido)-1,2,3,6-tetrahedro-2,6-dioxopyrimidine-4-carboxylic acid (H2ampa) with [Re(CO)5Cl] in ethanol led to the formation of a zwitterionic rhenium(I) complex [Re(CO)3(H2O)(amef)] [amef = {5-(5-ammoniumpyrimidine-2,4(1H,3H)-dioxamido)- 1,2,3,6-tetrahedro-2,6-dioxopyrimidine-4-ethylformate}]. The chelating ion amef was formed from the combined tricarbonylrhenium(I)-catalysed esterification and aminoprotonation of H2ampa (see Scheme 1) and coordinates to the fac-[Re(CO)3]+ core as a dianionic bidentate N,N-donor chelate via the amido nitrgens.
25
Cardey, Bruno. "Etude théorique des mécanismes d'oxydation de thiols en milieu d'intérêt biologique." Besançon, 2007. https://tel.archives-ouvertes.fr/tel-00435559.
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26
Mureau, Natacha. "Nouveaux précurseurs F-alkylés issus de la condensation malonique : application à la synthèse de tensioactifs hautement fluorés." Nice, 2001. http://www.theses.fr/2001NICE5598.
Testo completoAbstract (sommario):
Le but de ce travail est la synthèse de nouvelles molécules tensioactives hautement fluorées. Pour l'atteindre, nous avons préparé de nouveaux précurseurs F-alkylés à partir de la condensation malonique appliquée aux iodures de 2-F-alkyléthyle : RFC2H4CH(NCO)2, RF(CH2)3CO2H, RF(CH2)4OH, RF(CH2)4Br, RF(CH2)4SH, RF(CH2)4O2CCH2Br, RF(CH2)4OCH2CH(O)CH2. Cette voie de synthèse, peu onéreuse, a été privilégiée pour deux raisons principales. D'une part, elle permet de faire varier de façon illimitée l'espaceur hydrocarboné n séparant la chaîne perfluorée, RF, de la partie fonctionnalisée, X, de la molécule pour accéder, avec des rendements élevés, aux homologues supérieurs [RF(CH2)nX, n > 2]. D'autre part, elle permet d'obtenir des synthons clés difonctionnalisés de type [RF(CH2)n-1CHX2, n>2]. Les molécules synthétisées sont : des tensioactifs ioniques de type ammonium et bisammonium quaternaires possédant respectivement une chaîne hydrocarbonée ou un espaceur polyméthylène de longueur variable ; des tensioactifs non-ioniques soit de type diester possédant un coeur hydrophile oligooxyéthylé, soit de type polyhydroxylé, soit enfin de type dicarbamate possédant deux chaînes oxyéthylène. L'évaluation des propriétés tensioactives de l'ensemble de ces composés a été réalisée au travers de la détermination des concentrations micellaires critiques (CMC) et des tensions superficielles (?S) correspondantes. Les résultats ont révélé que les molécules synthétisées peuvent être classées parmi les plus performantes dans le domaine des surfactants.
27
Candela, Karine. "Sulfuration de terpénoi͏̈des." Nice, 2001. http://www.theses.fr/2001NICE5661.
Testo completoAbstract (sommario):
Des essais de sulfuration et de réduction entrepris sur huit terpénoi͏̈des modèles ont été réalisés pour mettre au point une méthode de synthèse de mercaptans terpénoi͏̈diques. La thioépoxydation effectuée par le système DMTF/TFA a permis la synthèse stéréospécifique de cinq épisulfures et deux thiols allyliques. La thioacétylation radicalaire par voie chimique et photochimique a conduit à l'obtention de neuf thioacétates avec une bonne régiosélectivité. La réduction des épisulfures et thioacétates par LiAlH4 a conduit, avec des rendements modérés à bons (28-98%), aux mercaptans terpénoi͏̈diques correspondants qui ont fait l'objet d'une analyse olfactive. L'étude spectroscopique approfondie par RMN 2D sera très utile pour l'identification de molécules présentant des squelettes voisins et servira d'outil de référence si ces molécules venaient à être trouvées dans la nature<br>The purpose of this work was to examine the sulfuration of a range of terpenoids and to obtain reduction products (terpenoids thiols) having potential interest for the fragrances and the flavors field. Thioepoxydation reaction performed with the DMTF/TFA system led to the formation of two allytic thiols and five episulfides in moderate yield with good stereoselectivity. Free-radical addition of thioacetic acid achieved on several terpenoids gave nine thioacetates in moderate yield with good regioselectivity. The reduction of those sulfur-containing terpenoids with LiAIH4 furnished, in good yield (23 to 98%), a variety of thiols whose organoleptic properties were investigated. In conclusion more than twenty sulfur-containing terpenoids have been prepared. Among them twenty are new to this work. Some of them required 2D-NMR experiments for unambiguous assignments of stereochemistry and structural elucidation
28
Amato, Claire. "Surfaces fonctionnalisées mixtes d'alcanethiols et d'aminothiols polyfluorés comme nouvelle plate-forme d'élaboration de biopuces." Montpellier 2, 2004. http://www.theses.fr/2004MON20108.
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29
Calais, Christophe. "Etude de la réduction du diphényldisulfure et de ses dérivés para substitués en présence de catalyseurs sulfures." Lyon 1, 1992. http://www.theses.fr/1992LYO10206.
Testo completoAbstract (sommario):
L'etude de la reduction des diphenyldisulfures a ete realisee en reacteur gaz-liquide-solide. L'exploration systematique des parametres experimentaux a permis de definir les conditions operatoires permettant de s'affranchir des phenomenes de transferts de matiere. Dans ces conditions experimentales, la determination de l'activite de diverses phases sulfures montre que ces catalyseurs ne se distinguent que par leur niveau d'activite car une selectivite en thiol de 100% est observee quelle que soit la nature du catalyseur. Sur ces systemes catalytiques, la presence simultanee de cations non completement coordines et de groupements sulfhydriles est indispensable pour conferer aux systemes des proprietes catalytiques. La presence de substituants electro-attracteurs ou donneurs induit une diminution de reactivite qui ne depend pas des effets electroniques. La modelisation moleculaire de ces molecules suggere que les effets geometriques sont par contre importants. En effet, de par leur conformation, l'interaction substituant-catalyseur rend la liaison s-s inaccessible au site catalytique
30
Broan, Christopher John. "A mechanistic study of the acid and base catalysed reactions of thiourea, 1-substituted thioureas and 1,3 -disubstituted thioureas with 1,2-diketones." Thesis, University of St Andrews, 1989. http://hdl.handle.net/10023/14978.
Testo completoAbstract (sommario):
Thiourea, 1-substituted thioureas and 1,3-disubstituted thioureas react under acidic or basic catalysis with 1,2-diketones to give a wide variety of products. The nature of the product or products depends on the conditions used, the degree of substitution of the thiourea and on the nature of the aromatic or aliphatic groups attached to the dicarbonyl unit of the diketone. The mechanisms of formation of the various products have been investigated by a variety of techniques, including the determination of rate equations by ultraviolet spectroscopy, the influence of side group substituents on the rate and course of the reactions and the synthesis of putative Intermediates on the reaction pathway. The single most informative technique used was, without a doubt, the detection of low concentrations of transient intermediates and side products by the application of carbon-13 nmr spectroscopy to the reaction as it progressed using carbon-13 labelled di ketones to enhance the detection of low level intermediates. It has been shown convincingly that some organic reactions proceed via a small number of irreversible processes amongst a very complex set of more rapid equilibrium processes.
31
MAZEAUD, BRIGITTE. "Modification chimique de polyisobutenes porteurs d'extremite vinylidene par des thiols." Paris 6, 1992. http://www.theses.fr/1992PA066246.
Testo completoAbstract (sommario):
La modification de polyisobutenes a terminaisons vinylidene par des thiols est effectuee en presence de generateurs de radicaux libres qui sont soit des amorceurs de type percarbonates ou aibn, soit l'irradiation ultraviolette. La reaction est une addition de type anti-markovnikov de la fonction thiol sur la double liaison. Les pib modifies obtenus sont caracterises essentiellement par spectrometrie ir et rmn du proton. Dans un premier temps, une etude realisee avec le mercaptoethanol a mis en evidence l'influence de divers facteurs tels que la temperature, la presence de solvant ou le rapport fonctions thiol sur extremites vinylidene. La modification du pib par le mercaptoethanol ne s'effectue qu'en presence d'un apport minimal d'oxygene (oxygene de l'air), en solution et avec un exces de thiol. L'influence de la nature du thiol est examinee dans la deuxieme partie et permet de generaliser le procede. La comparaison des resultats obtenus avec differents thiols montre que des conditions optimales doivent etre recherchees pour chaque cas. La derniere partie decrit d'une part la synthese d'elastomeres realisee a partir de pib modifies par des mercaptopropyltrimethoxy et triethoxysilanes par hydrolyse et condensation des fonctions si-(or)#3 et, d'autre part la synthese de copolymere en peigne obtenus par greffage des pib sur des polysiloxanes porteurs de fonctions thiol
32
Hallberg, Åsa. "Thermodynamic stability of methylmercury complexes with low molecular mass thiols." Thesis, Umeå universitet, Kemiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-137289.
Testo completo
33
Mingat, Gaelle. "Tertiary thiols via stereospecific α-arylation of lithiated allylic thiocarbamates". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/tertiary-thiols-via-stereospecific-alphaarylation-of-lithiated-allylic-thiocarbamates(91e495f6-9924-4e96-8c23-50e84ea205ac).html.
Testo completoAbstract (sommario):
This thesis describes the work carried out on the lithiation and rearrangement of N-aryl- and N-vinyl allylic thiocarbamates, with the aim of preparing a wide range of versatile tertiary thiols. The synthesis of the racemic allylic starting materials has been achieved through in situ [3,3]-sigmatropic rearrangement of O-allylthiocarbamates to their S-counterparts (II.A). The enantioselective version relies either on asymmetric metal catalysis (achiral substrates) or stereospecificity (enantiopure substrates) in the [3,3]-sigmatropic rearrangement. Lithiation followed by N to C aryl migration proceeds in generally good to excellent yields, with both electron-poor and electron-rich rings. The scope and the influence of various substituents at Cα or on the allylic double bond are presented in Section II.B.1. Section II.B.2 proposes a mechanistic pathway and details NMR studies carried out to get structural data in the α-thioallyllithium intermediates. Investigations of the stereospecificity of the rearrangement show that most rings migrate without loss of enantioenrichment in substrates bearing an unsubstituted allylic double bond (II.B.3.a). Complete enantiospecificity with all rings has been achieved in thiocarbamates bearing a cyclohexyl-substituted double bond (II.B.3.b). Section II.C reports the results obtained in the N to C transfer of non-aromatic groups. Excellent enantiospecificities have been achieved in the migration of a vinyl substituent, although yields remain moderate. Higher yields can be obtained but they come along with lower enantiomeric ratios. Section II.D details the transformations undertaken in the rearranged tertiary allylic thiocarbamates. A wide range of tertiary thiols has been obtained with good to excellent yields. Functionalisation of the allylic double bond in these hindered substrates was not straightforward. Eventually, ring-closing metathesis in S-allyl sulfides allows the preparation of biologically interesting 2,5-dihydrothiophenes bearing a highly enantioenriched quaternary centre. Finally, evidence for retentive aryl migration in allylic thiocarbamates is outlined in Section II.E. Circular dichroism experiments were carried out in the derivatised 2,5-dihydrothiophenes and compared with predictions obtained via DFT calculations for both enantiomers of a model compound. The absolute configuration of the 2,5-dihydrothiophenes and their tertiary thiocarbamate precursors has been unambiguously established, confirming a retentive pathway in both aryl and vinyl migrations.
34
Roland, Aurélie. "Influence des phénomènes d'oxydation lors de l'élaboration des moûts sur la qualité aromatique des vins de Melon B. et de Sauvignon Blanc en Val de Loire." Thesis, Montpellier, SupAgro, 2010. http://www.theses.fr/2010NSAM0016/document.
Testo completoAbstract (sommario):
Afin de caractériser les moûts de Melon B. et de Sauvignon Blanc en composition et de modéliser leur profil d'oxydation, diverses méthodologies analytiques quantitatives ont été développées et validées. La quantification par dilution isotopique des précurseurs de thiols a nécessité la synthèse de molécules marquées qui ont également servies de traceurs lors d'études de filiation dans des milieux complexes. Ainsi, au cours de la fermentation alcoolique, nous avons pu démontrer que le S-3-(hexan-1-ol)-glutathion (G3MH) et la S-4-(4-méthylpentan-2-one)-glutathion (G4MMP) sont métabolisés par la levure et libèrent le 3-mercaptohexan-1-ol (3MH) et la 4-méthyl-4-mercaptopentan-2-one (4MMP) avec des rendements de conversion molaires proches de 4,4 % et 0,3 % respectivement. La modélisation des phénomènes d'oxydation à l'échelle laboratoire a permis par ailleurs de vérifier, comme le laissaient supposer leurs structures chimiques, que les précurseurs de thiols ne sont pas dégradés par les mécanismes oxydatifs affectant les moûts. Au contraire, une formation de G3MH concomitante avec le pic de production du Grape Reaction Product (GRP) est observée. La validation de ces observations à l'échelle industrielle a été conduite par comparaison des pressurages traditionnel et inerté. L' élaboration d'un moût de Melon B. sous gaz inerte n'est pas favorable à la production de G3MH d'origine pré-fermentaire, et a pour conséquence une diminution des teneurs en 3MH dans les vins correspondants, sans pour autant, déprécier les qualités organoleptiques des vins jeunes. Pour le Sauvignon Blanc, le potentiel aromatique de type thiol n'est pas affecté par le type de pressurage, mais une diminution très significative en 3MH dans les vins issus des cuvées obtenues sous gaz inerte est observée. La voie du (E)-2-hexènal qui est certainement impliquée, pourrait expliquer cette perte aromatique. Ainsi, de manière globale, dans nos conditions expérimentales, une oxydation ménagée et raisonnée des moûts de Melon B., et dans une moindre mesure de Sauvignon Blanc, est favorable à la qualité aromatique des vins du Val de Loire<br>In order to characterize Melon B. and Sauvignon Blanc musts in composition and to study their oxidation profiles, several analytical methodologies have been developed and validated. The quantification of thiols precursors by Stable Isotope Dilution Assay required the synthesis of labeled molecules, which have been used either as analytical standards or as tracers for relationship studies in complex matrices. Thus, we established that, during the alcoholic fermentation, the S-3-(hexan-1-ol)-glutathione (G3MH) and the S-4-(4-méthylpentan-2-one)-glutathione (G4MMP) are metabolized by the yeast to release the 3-mercaptohexan-1-ol (3MH) and the 4-méthyl-4-mercaptopentan-2-one (4MMP) with molar conversion yields close to 4.4 % and 0.3 % respectively. Oxidation mechanisms study at laboratory scale demonstrated that aromatic potential was not affected by oxidative reactions, as expected in regard to their chemical structures. On the contrary, the G3M H was produced in the same time as the Grape Reaction Product peak (GRP). The validation of these observations at industrial scale was conducted by comparing traditional and inerted pressing systems. The elaboration of a Melon B. must under inert gas was not in favor of a G3MH pre-fermentary production, which induced a decrease of 3MH concentration in wine without affecting the organoleptic qualities of young wines. For Sauvignon Blanc must, the aromatic potential was not affected by the kind of pressing systems but a significant decrease in 3MH was observed in the wines obtained with juices from the beginning of pressing. The E-(2)-hexenal pathway could certainly explain such aromatic losses. Thus, under our experimental conditions, a mild and controlled oxidation of Melon B. must and, in a certain extend of Sauvignon Blanc must, is in favor of the aromatic quality of wines from Loire Valley
35
Stålgren, Johan Jim Roger. "Adsorption of Surfactants at the Solid-Liquid Interface : A Quartz Crystal Microbalance Study." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3291.
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Handley, Kevin Frank. "The mechanism of toxicity of nitrobenzenes." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308365.
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37
Burollaud, Thierry. "Etude du site actif du récepteur des glucocorticoi͏̈des : modalités comparées de son interaction avec les stéroi͏̈des agonistes et antagonistes." Lille 1, 1993. http://www.theses.fr/1993LIL10091.
Testo completoAbstract (sommario):
Nous avons étudié la sensibilité sélective de liaison aux stéroïdes du récepteur des glucocorticoïdes (rgc) soumis à un traitement par des réactifs spécifiques des thiols (alkylmaleimides). Des stéroïdes agonistes (ta,dex,ru26988,ru28362, cor) et antagonistes (ru486,dxb) ont été testés. Des réactions de compétition en absence de réactif ont montré que ces ligands se lient au rgc au niveau du même site de liaison. La liaison de la ta au récepteur libre préincube avec différentes alkylmaleimides est presque totalement inhibée contrairement à celle du ru486 plus ou moins affectée selon la taille du substituant alkyl. Des réactions d'échange de stéroïdes en présence d'acétonitrile montrent que le ru486 semble incapable de protéger le site de liaison des effets de la nem contrairement à la ta. Ce manque de protection peut être lié à la présence du substituant volumineux en 11 bêta du ru486 car, en absence de celui-ci le ru26988 et le ru28362, qui portent cependant la même chaîne latérale 17 alpha que le ru486, protégent le site. De plus le blocage par le ligand de l'action de la nem semble indépendant de son activité biologique. En effet, le cor ne semble offrir aucune protection du site contrairement au dxb. Tous ces faits montrent que les ligands caractérisés par un substituant volumineux en 3 (cor) ou en 11 (ru486) sont positionnés différemment dans le site par rapport aux ligands habituels (ta,dex). Parallèlement, l'interaction du rgc avec différents dérivés du ru486, stéroïdes marqueurs d'affinité potentiels, a été étudiée. Deux dérivés présentent un taux d'échange relativement faible vis-à-vis de la dex même en présence d'acétonitrile. Ils semblent pourtant stabiliser le récepteur sous la forme non transformée théoriquement échangeable à un taux élevé. Ces résultats suggèrent qu'ils forment avec le rgc des complexes covalents non échangeables
38
Chan, Lai-fung. "Synthesis, structures and properties of metal-metal bonded transition metal with organothiolate ligands." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40687703.
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Thiem, Deborah A. 1964. "Synthesis, purification, and metal complex formation properties of methyl 3-mercaptopropionate and solubility and stability constants of meso-2,3-dimercaptosuccinic acid." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277043.
Testo completoAbstract (sommario):
Methyl 3-mercaptopropionate was synthesized from 3-mercaptopropionic acid and purified by extraction into chloroform and column chromatography. The percent purity of the purchased material was determined by an iodine titration. Methyl 3-mercaptopropionate formed an insoluble complex with lead (II) when the pH was greater than 3. It also complexed with cobalt (II). The solubility of meso-dimercaptosuccinic acid was estimated by a spectrophotometric method using 5,5-dithiobis(2-nitrobenzoic acid) since the iodine titration did not give quantitative results. The acid dissociation constants were determined potentiometrically; two methods of calculation were used. Attempts to prepare crystals of the lead (II) complex of meso-dimercaptosuccinic acid in the following gels: agar, agarose, and gelatin, were unsuccessful.
40
Cardey, Bruno. "Étude théorique des mécanismes d'oxydation de thiols en milieu d'intérêt biologique." Phd thesis, Université de Franche-Comté, 2007. http://tel.archives-ouvertes.fr/tel-00435559.
Testo completoAbstract (sommario):
La compréhension du phénomène de stress oxydant est devenue un des enjeux majeurs de la biochimie, en particulier depuis le début des années 70. Ce déséquilibre de la balance d'oxydoréduction au sein des cellules est impliqué dans un si grand nombre de pathologies graves (dont la plupart des cancers, pour ne citer qu'eux) qu'il est devenu crucial de cerner ses origines et ses mécanismes, pour envisager une prévention et des traitements plus efficaces. Nous nous sommes intéressés aux interactions existant entre les thiols (qui sont les acteurs principaux de la lutte antioxydante) et trois agents oxydants importants : le peroxyde d'hydrogène et les radicaux hydroxyle et superoxyde. Malgré le nombre important d'études dédiées à ce sujet, les mécanismes de ces réactions n'étaient pas clairement identifiés, c'est pourquoi nous avons pensé qu'une étude théorique pourrait apporter des éclaircissements utiles. En effet, la connaissance des mécanismes de réaction permettrait d'une part de faciliter l'interprétation des données expérimentales, et d'autre part d'envisager plus efficacement d'éventuels traitements basés sur l'inhibition ou la catalyse de ces réactions. Nous avons utilisé des méthodes ab initio de chimie quantique permettant d'atteindre une précision "chimique", par exemple la méthode par interaction de configuration quadratique (QCI). Ces techniques impliquent des temps de calcul relativement longs, ce qui nous a incités à modéliser les thiols par de petites molécules comme le méthanethiol et le résidu cystéine. Les mécanismes des trois réactions étudiées ont été identifiés, et nos travaux ont démontré l'importance que peuvent avoir les effets environnementaux (comme la présence de liaisons hydrogène ou la constante diélectrique du milieu) sur les cinétiques de réaction.
41
Schreyer, Suzanne Katherine. "Development of a synthetic enzyme for detection and quantitation of thiols." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0005/MQ40196.pdf.
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42
Jones, Arfon Harris. "Self-assembled monolayers of ferrocene-terminated alkyl thiols on gold surfaces." Thesis, Bangor University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340954.
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43
Biojout, Alexandre Denis. "Investigations into the reactivity of thiols and disulfides at membrane interfaces." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489365.
Testo completoAbstract (sommario):
The membrane is a key component of cells as it acts as a barrier with the extracellular matrix, preventing alien entities trom entering the cell unnindered. It also provides the medium for membrane embedded proteins to bind and react to small molecule messengers and with other cells. The research described in this thesis is focused on the study of the thiol-disulfide reaction at the membrane interfaces in order to understand how this environment affects reactivity and mechanism relative to aqueous solution. This knowledge informs the design of artificial biomimetic systems based on vesicles, which have long been used as the cell membrane model of choice.
44
Patel, Hanif M. S. "Studies on the nitrosation of thiols in relation to vasodilatory action." Thesis, Durham University, 1989. http://etheses.dur.ac.uk/6728/.
Testo completoAbstract (sommario):
A kinetic study of the nitrosation of L-cysteine, L-cysteine methyl and ethyl esters, N-acetyl-L-cysteine and glutathione by isopropyl nitrite in acid solution at 25 C was undertaken. The thiols exhibited identical rate laws and in all cases the observed rate constant was reduced by added isopropyl alcohol. The results were found to be consistent with the mechanism in which a rapid reversible acid-catalysed hydrolysis of isopropyl nitrite occurs to give nitrous acid, which then in its protonated form effects nitrosation. The third-order rate constant for the nitrosation of the thiols by isopropyl nitrite and the equilibrium constant for the formation of isopropyl nitrite were found to be in good agreement with the literature values obtained by direct measurement. A similar kinetic study of the nitrosation of L-cysteine, L-cysteine methyl and ethyl esters, N-acetyl-L-cysteine, thioglycolic acid and glutathione by various alkyl nitrites, in water at 25 C , in the pH range 6-13 was undertaken. The pH dependence of the rate constant is consistent with a mechanism involving a direct nitrosation by alkyl nitrites with the thiolate anion (RS(^-)) of the thiol. A quantitative kinetic analysis yielded macroscopic and microscopic pKa values for RSH ionisation in good agreement with the literature values. One exception is L-cysteine where the microscopic, pKp, value (for NH(_2)RSH → NH(_2)RS(^-)) differs significantly from the literature value. In the case of simple alkyl nitrites (ethyl, isopropyl, isoamyl and t-butyl nitrites) steric effects appear to be the major influence in reactivity whereas electron-withdrawing substituents in the β-position greatly enhanced the rate constant. The results were found to satisfy Taft's equation and thus a correlation between structure and reactivity of the alkyl nitrites with the thiols was established. This work shows that at least in vitro a direct and rapid reaction occurs between alkyl nitrites and thiols at pH values likely to be encountered in vivo. This confirms that such reactions could occur in vivo and could be an important feature of the chain of events occurring during the vasodilatory action of alkyl nitrites. Finally a preliminary investigation of the reaction of glyceryl trinitrate with cysteine, in oxygen and oxygen-free nitrogen atmosphere, in the pH range 6-13 was undertaken. In this case no evidence was found for the formation of S-nitrosocysteine or nitric oxide from glyceryl trinitrate in the presence or absence of cysteine. Thus the results could not confirm the hypothesis that glyceryl trinitrate owes its vasodilatory action to the formation of the intermediate, S-nitrosocysteine, from the reaction of nitric oxide (formed from glyceryl trinitrate) and cysteine.
45
Scrivens, Garry. "An EPR investigation into the catalytic oxidation of thiols by peroxides." Thesis, University of York, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284121.
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Nikolantonaki, Maria. "Incidence de l’oxydation des composés phénoliques sur la composante aromatique des vins blancs." Thesis, Bordeaux 2, 2010. http://www.theses.fr/2010BOR21770/document.
Testo completoAbstract (sommario):
Les réactions d'oxydation impliquant les composés phénoliques semblent induire des modifications non négligeables du profil chimique et sensoriel des vins. Les travaux concernent l’étude des mécanismes réactionnels impliquant certains thiols volatils, contributeurs de l’arôme distinctif et de la complexité des vins des différents cépages avec les composés phénoliques oxydés des vins blancs, principalement les flavan-3-ols. En solution modèle de composition proche du vin, une réactivité différente des thiols volatils selon leur nature chimique vis à vis des formes oxydées des flavan-3-ols a été établie. La synthèse et la caractérisation des adduits par RMN entre les principaux composés phénoliques des moûts et des vins blancs et le 3-sulfanylhexanol, présentant des nuances d’agrumes, a ensuite été réalisée en conditions d’oxydation chimique et enzymatique. La suivi cinétique de la formation des adduits par CLHP-ESI-SM a permis de mettre en évidence une réactivité du thiol spécifique vis à vis d’un substrat polyphénolique, d’établir le rôle catalytique des métaux (Fe2+) et la capacité antioxydante du dioxyde de soufre vis à vis de ces mécanismes réactionnels. La compréhension de mécanismes fondamentaux de la réactivité de la (+)-catéchine et de la (-)-épicatéchine en conditions œnologiques avec les thiols volatils nous a permis de décliner les travaux à l’étude de l’influence de la présence des flavan-3-ols au cours de la vinification et de l’élevage des vins sur ces composants de l’arôme des vins blancs<br>Oxidation reactions involving phenolics might change wines chemical and sensory profile. The present work concern the study of reactional mechanisms implying certain volatile thiols, responsible of distinctiveness and complexity of various wines, with white wines oxidized phenolic compounds, mainly flavan-3-ols. In a model wine solution, a different volatile thiol reactivity pattern according to their chemical nature with respect to oxidized flavan-3-ols forms was established. The adducts synthesis and characterization by NMR between the principal white musts and wines phenolic compounds and the 3-sulfanylhexanol, presenting citrus fruits nuances, were carried out under chemical and enzymatic oxidation conditions. Their formation monitoring by HPLC-ESI-MS highlighted a specific reactivity of thiol with polyphenolic substrate and established the catalytic role of metals (Fe2+) as well as, the antioxidant effect of sulphur dioxide into these mechanisms. The comprehension of fundamental mechanisms for the reactivity of (+)-catechin and of (-)-epicatechin with volatile thiols in oenological conditions enabled us to elucidate the influence of flavan-3-ols into white wines aroma compounds during wine making and ageing
47
Bonnaffoux, Hugo. "Identification de nouveaux précurseurs de thiols variétaux dans les moûts et implication dans les mécanismes de révélation du potentiel aromatique." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS016/document.
Testo completoAbstract (sommario):
La mise au point d’une méthode d’analyse par UPLC-MS/MS et dilution isotopique nous a permis d’identifier pour la première fois dans un moût le S-3-(hexan-1-ol)--glutamyl-cystéine (GluCys-3MH). Suite à cette découverte, l’étude des interconversions entre les glutathionylés, dipeptides et cystéinylés S-conjugués au 3-mercaptohexan-1-ol (3MH) ou à la 4-mercapto-4-méthyl-pentan-2-one (4MMP), a permis de mettre en évidence deux nouvelles formes de précurseurs. Le suivi de l’évolution de ces différents composés au cours de fermentations alcooliques à l’échelle laboratoire a permis de clarifier leur rôle de précurseurs et d’établir les éventuels mécanismes d’interconversion. Par ailleurs, à travers plusieurs expérimentations viticoles et œnologiques conduites à l’échelle pilote en Languedoc et Val de Loire pendant trois années consécutives, des éléments nouveaux ont pu être apportés quant à l’impact de la maturation du raisin et son hétérogénéité, ainsi qu’à l’importance des opérations pré-fermentaires comme la macération pelliculaire ou la stabulation sur bourbes<br>The development of a method using UPLC-MS/MS and stable isotope dilution assay allowed us to identify for the first time the S-3-(hexan-1-ol)--glutamyl-cysteine (GluCys-3MH) in musts. Following this discovery, the study of interconversions between glutathione, dipeptides and cysteine S-conjugates to 3-mercaptohexan-1-ol (3MH) or 4-mercapto-4-methyl-pentan-2-one (4MMP) highlighted two new forms of precursors. The evolution monitoring of these compounds during alcoholic fermentations at laboratory scale allowed us to clarify their role as precursors and to establish the possible interconversion mechanisms. In addition, through several viticultural and oenological experiments carried out at pilot scale in Languedoc and Val de Loire during three consecutive years, new elements could be … about the impact of grape ripening and its heterogeneity, as well as the importance of prefermentative processes, such as skin maceration and must conservation on lees
48
Delauney, Bernard. "Dosage des thiols d'intérêt biologique par CLHP : application au dosage du glutathion réduit dans le sang." Paris 5, 1989. http://www.theses.fr/1989PA05P041.
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49
Andersson, Anja. "Method development for the determination of thiols using HPLC with fluorescence detection." Thesis, Umeå universitet, Kemiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-59827.
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50
Spender, Jonathan. "Photostabilization of High-Yield Pulps Reaction of Thiols and Quinones with Pulp." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/SpenderJ2001.pdf.
Testo completo