Academic literature on the topic 'Thiols'

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.

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

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.

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.

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.

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.