Thiols

Dimethylsulphide (DMS) plays a major role in the global sulphur cycle. It has important implications for atmospheric chemistry, climate regulation, and sulphur transport from the marine to the atmospheric and terrestrial environments. In addition, DMS acts as an info-chemical for a wide range of organisms ranging from micro-organisms to mammals. Micro-organisms that cycle DMS are widely distributed in a range of environments, for instance, oxic and anoxic marine, freshwater and terrestrial habitats. Despite the importance of DMS that has been unearthed by many studies since the early 1970s, the understanding of the biochemistry, genetics, and ecology of DMS-degrading micro-organisms is still limited. This review examines current knowledge on the microbial cycling of DMS and points out areas for future research that should shed more light on the role of organisms degrading DMS and related compounds in the biosphere.

Rheumatoid arthritis (RA) is characterised by migration of activated phagocytes and other leukocytes into synovial and periarticular tissue. Activated oxygen species and other mediating substances from triggered phagocytes appear to exacerbate and perpetuate the rheumatoid condition. Iron excesses are capable of aggravating the arthritic inflammation, probably through their pro-oxidant potentials. In contrast, therapeutically given gold salts, through a lysosomal loading of the metal, inhibit the triggered cells, thereby reducing the toxic oxygen production. Pharmacological doses of zinc also may immobilise macrophages. Furthermore, the copper-zinc-containing enzyme SOD (superoxide dismutase) can act as a scavenger of toxic oxygen in the tissues. Therapeutic remission of RA has been obtained following intraarticular administration of SOD.

The biocatalytic synthesis of phenothiazones and related compounds has been achieved in an aqueous system under mild conditions facilitated by laccase oxidation. It was found that by coupling 2-aminoth-iophenol directly with 1,4-quinones, the product yields could be significantly increased compared to generating the 1,4-quinones in situ from the corresponding hydroquinones via laccase oxidation. However, laccase still proved to be pivotal for achieving highest product yields by catalyzing the final oxidation step. Furthermore, a difference in reactivity of aromatic and aliphatic amines toward 1,4-naphthoquinone is observed. This study provides a sustainable approach to the synthesis of a biologically important class of compounds.

The most commonly used solution in chrome plating bath is chromic acid (hexavalent Cr), and a considerable amount of mists is released into the air and consequently produce hazards to workers. Thus, the aim of this study was to evaluate whether the biomarker of exposure to metals, specially Cr levels, presents associations with hematological and biochemical parameters and if they can alter the activity of enzymes that contain thiol groups such as pyruvate kinase, creatine kinase, adenylate kinase, and δ-aminolevulinate dehydratase. Fifty male chrome plating workers were used for exposed group and 50 male non-exposed workers for control group. For that, biological monitoring was performed through quantification of metals on total blood and urine by inductively coupled plasma mass spectrometry (ICP-MS) and enzyme activity was performed by spectrometry in erythrocytes. In addition, chromium levels in water was quantified and ecotoxicology assay was performed with Allium cepa test. The results demonstrated that blood and urinary chromium levels in exposed group were higher than the control group (p < 0.0001). Furthermore, decreased activity of enzymes was found in those that contain thiol groups from exposed group when compared with the control group (p < 0.001). The water analysis did not present a statistical difference between control and exposed groups (p > 0.05), demonstrating that water did not seem to be the source of contamination. In summary, our findings indicated some toxicology effects observed in the exposed group, such as thiol enzyme inhibition, mainly associated with occupational exposure in chrome plating and besides the presence of other metals, and Cr demonstrated to influence the activity of the enzymes analyzed in this research.

The increasing use of silver nanoparticles (AgNPs) in consumer products raises the risk of human toxicity. Currently, there are no therapeutic options or established treatment protocols in cases of AgNPs intoxication. We demonstrated previously that thiol antioxidants compounds can reverse the cytotoxicity induced by AgNPs in Huh-7 hepatocarcinoma cells. Here, we investigated the use of N-acetylcysteine (NAC) against the systemic toxic effects of AgNPs (79.3 nm) in rats. Biochemical, histopathological, hematological, and oxidative parameters showed that a single intravenous injection of AgNPs (5 mg/kg b.w.) induced deleterious effects such as hepatotox-icity, potentially as a result of AgNPs accumulation in the liver. Treatment with a single intraperitoneal injection of NAC (1 g/kg b.w.) one hour after AgNPs exposure significantly attenuated all toxic effects evaluated and altered the bioaccumulation and release patterns of AgNPs in rats. The findings show that NAC may be a promising candidate for clinical management of AgNPs intoxication. ARTICLE HISTORY

Organothiol (R-SH) (OT) adsorption onto silver nanoparticles (AgNPs) in water was studied for a series of aromatic OTs including pmethylbenzenethiol (p-MBT), p-benzenedithiol (p-BDT), and 2-mercaptobenzimidazole (2-MBI). Unlike the common view that OT forms monolayer adsorption on AgNPs, we found that these aromatic OTs continuously reacted with AgNPs through formation of RS−Ag complexes until complete OT or AgNP consumption occurred. The RS−Ag complex can remain on the AgNP surface, converting the AgNPs into core−shell structures. The OT adsorption onto AgNPs occurs predominately through reaction with silver oxide present on the AgNP surfaces before the OT addition or formed from environmental oxygen in the presence of OT. The RS−H protons are completely released when both p-MBT and 2-MBI reacted with AgNP, Ag 2 O, and AgNO 3 . However, a substantial fraction of S−H bonds remained intact when p-BDT, the only dithiol used in this work, is adsorbed on AgNPs or reacted independently with Ag 2 O and AgNO 3 . The new insights from this work should be important for understanding OT interaction with AgNPs in water and the SERS spectra of the OT adsorbed onto AgNPs.

A Glutathione (GSH) optical sensor with high sensitivity and exceptional selectivity was developed using one-step synthesized-upconversion nanoparticles (UCNPs, NaLuF4:Gd3+,Yb3+,Er3+) in conjunction with a Rhodamine B derivative (RBD). RBD was loaded on the surface of the UCNPs though non-covalent bonding to serve as an energy acceptor, while UCNPs served as energy donors. The sensor based on a coupling fluorescence resonance energy transfer (FRET) process at an excitation of 980 nm wavelength from UCNP to RBD with a ringopening process of RBD after the addition of GSH. The sensing probe exhibits a remarkable
limit of detection (LOD = 50 nM) for GSH through the enhancement of the fluorescence intensity of RBD at 592 nm, together with a concomitant reduction in the green band of the UCNPs. In addition, the sensing mechanism, characterization of UCNPs, and the selectivity of the fluorescence sensor toward GSH were discussed. The proposed sensor was evaluated on real human serum and urine samples and demonstrated as a highly selective and sensitive probe for the detection of GSH.

The first off–on probe, Mito-TRFS, for imaging the mitochondrial thioredoxin reductase (TrxR2) in live cells was reported. In a cellular model of Parkinson’s disease (PD), Mito-TRFS staining discloses a drastic decline of the TrxR2 activity, providing a mechanistic link of TrxR2 dysfunction to the etiology of PD.

A thiol-selective 2-methyl-3-phenacrylate scaffold with spatiotemporal control over delivery of a cargo is reported. The half-lives of decomposition could be tuned from 30 min to 1 day and the scaffold's utility in thiol-inducible fluorophore release in cell-free as well as within cells is demonstrated.

Photonic experiments are of key importance in life sciences but light-induced side effects are serious confounding factors. Here we introduce roNa V 2, an engineered voltage-gated Na + channel harboring a selenocysteine in its inactivation motif, as a non-photonic, sensitive, gateable, and reversible sensor for membrane-delimited reactive species. roNa V 2 allows for the assessment of chemical modification induced in fluorescence microscopy settings with high sensitivity and time resolution and it demonstrates the usefulness of ion channels as highly sensitive reporters of membrane processes. Cellular reactive species (RS), e.g., superoxide (O 2 −⋅), hydroxide (HO ⋅), hydrogen peroxide (H 2 O 2), and hypochlorous acid (HClO) play crucial roles in physiological processes, such as signal transduction, activation of nuclear transcription factors, gene expression, and immune regulation 1–3. However, excess RS modify lipids, proteins, and nucleic acids, and are often associated with adverse consequences such as neurodegeneration, ath-erosclerosis, diabetes, sepsis, and cancer 4. RS differ in their production, concentration, distribution, lifetime, molecular targets, and biological functions. Therefore, there is a clear demand for sensitive probes to precisely monitor cellular RS with spatio-temporal resolution to understand the multifaceted role of cellular RS in cell physiology. Recently, mutants and fusions of genetically encoded GFP (green fluorescent protein), for example, reduction and oxidation sensitive variants roGFP2 5 and Grx1-roGFP2 (Grx = glutaredoxin) 6 , received much attention for cellular RS monitoring. roGFP2 is a genetically engineered fluorescent redox reporter, which was developed by inserting a dithiol-disulfide pair into GFP. The breakage and the formation of the disulfide bridge in roGFP2 leads to a differential change in fluo-rescence at 400 nm and 470 nm excitation wavelength, thus yielding a ratiometric signal that reports on oxidative changes in its local environment. Fusion of human glutaredoxin-1 to roGFP2 provides strongly accelerated formation of a disulfide bridge and, hence, increases the sensitivity of Grx1-roGFP2 in the physiologically relevant range for glutathione-mediated RS modifications 6. These fluorescent reporters offer several useful features, such as the choice of localized sub-cellular targeting, real-time RS detection, and ratiometric observation that overcome artifacts arising due to photo-bleaching and inhomogeneous distribution of the sensors. However, there is the inherent problem of phototoxicity that can lead to lasting irreversible destruction of cellular structures and may even result in immediate alteration of molecular function. Despite the obvious detrimental consequences of visible light in cell physiological studies, the issue of phototoxicity has been only infrequently considered in life science research 7. The presence of intracellular flavin-containing oxidases, the cytochrome system, heme-containing proteins, and tryptophan-rich proteins not only confound with fluorescence techniques, they may also act as cellular photosensitizers and constitute the major source of light-induced RS 8–10. Moreover, photo-activated GFP disturbs cellular redox homeostasis either by producing endogenous superoxide or altering the glutathione homeostasis 11–13. Therefore, the potential interference of blue light as used for GFP-based imaging with the cellular redox system clearly demands for alternative tools or probes for monitoring cellular RS. Previously, we have reported a genetically engineered voltage-gated Na + (Na V) channel with a cysteine residue in its inactivation domain (roNa V 1; rNa V 1.4 mutant M1305C, also termed IFC) as a non-photonic RS sensor delimited to the cell membrane 14. Na V channels activate (open) and inactivate (close) rapidly in response to

Self-assembled monolayers (SAMs) containing azobenzene moieties are very attractive for a wide range of applications, including molecular electronics and photonics, bio-interface engineering and sensoring. However, very little is known about the aggregation and photoswitching behavior that azobenzene units undergo during the SAM formation process. Here, we demonstrate that the formation of thiol based SAMs containing azobenzenes (denoted as AzoSH) on gold surfaces is characterised by a two step adsorption kinetics, while a three-step assembly process has been identified for dithiolane-based SAMs containing azobenzenes (denoted AzoSS). The H-aggregation on the AzoSS SAMs was found to be remarkably dependent on the time of self-assembly, with less aggregation as a function of time. While photoisomerization of the AzoSH was suppressed for all different assembly times, the reversible trans–cis photoisomerization of AzoSS SAMs formed over 24 hours was clearly observed upon alternating UV and Vis light irradiation. We contend that detailed information on formation kinetics and related optical properties is of crucial importance for elucidating the photoswitching capabilities of azobenzene based SAMs

This study was carried out with fresh Australian lager beer which was sampled directly off the production line, the same samples aged for 12 weeks at 30 °C, and the vintage beer which was kept at 20 °C for 5 years. Characteristic Australian lager flavour was maintained in the fresh and vintage beers but was lost in the aged beer. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and free thiol group labelling analyses of beer proteins found that this flavour stability correlated with the presence of an unknown 10 kilodaltons (kDa) protein with a higher level of free thiols. The protein was purified by size-exclusion chromatography, then peptide sequencing and database matching identified it as the barley lipid transfer protein (LTP1). Further characterisation

A series of N-acetyl-S- [(3-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)methyl]-L-cysteine conjugates were obtained in good yields by acid-catalyzed condensation of substituted 2-hydroxy-1,4-naphthoquinones with N-acetyl-L-cysteine and paraformaldehyde. Based on this reaction, a first synthesis of fibrostatins B, C, and D was developed.

Hünlich’s base modification has resulted in introducing a series of versatile Λ-shaped building blocks presented in this work. The methods are optimized to provide convenient approaches in the quicker production of these new building blocks in low-cost and low-risk.

Transgenic tobacco (Nicotiana tabacum cv. LA Burley 21) lines expressing three genes encoding enzymes thought to be critical for the efficient production of phytochelatins, (i) serine acetyltransferase (EC 2.3.1.30) involved in the production of O-acetylserine, the cysteine precursor, (ii) c-glutamylcysteine synthetase (EC 6.3.2.2) involved in the production of c-glutamylcysteine, the precursor of glutathione, and (iii) phytochelatin synthase (EC 2.3.2.15), were obtained and analysed for non-protein thiol content and cadmium accumulation. After a 3 week exposure to 15 lM CdCl 2 , plants expressing transgenes (either separately or in combination) had increased cadmium concentration in roots but not in shoots compared with the wild type. Nearly all transgenic lines analysed had more non-protein thiols than the wild type. The greatest effects (about 8-fold elevation of thiols) were found in one of the lines simultaneously expressing the three transgenes. Despite the fact that a multi-transgene strategy described in this work resulted in a strong increase in the levels of several classes of non-protein thiols in transgenic plants, other factors appeared to restrict cadmium accumulation in shoots.

Objective: Alpha-lipoic acid (ALA) as a strong antioxidant has a protective effect. This study was designed to assess whether supplementation of maturation medium with ALA during in vitro maturation (IVM) can attenuate the toxic effect of ethanol. Materials and Methods: In this experimental study, to assess the antioxidant capacity of ALA challenged by 1% ethanol during in vitro maturation, immature ovine oocytes were exposed to 1% alcohol in the presence or absence of 25 µM ALA during oocyte maturation. The cumulus expansion index, intracellular reactive oxygen species (ROS), and thiol content levels were assessed in matured oocytes of various treatment groups. Consequently, the blastocyst formation rate of matured oocytes in various treatment groups were assessed. In addition, total cell number (TCN), cell allocation, DNA fragmentation, and relative gene expression of interested genes were assessed in resultant blastocysts. Results: The results revealed that alcohol significantly reduced cumulus cells (CCs) expansion index and blastocyst yield and rate of apoptosis in resultant embryos. Addition of 25 µM ALA to 1% ethanol during oocyte maturation decreased ROS level and elevated Thiolcontent. Furthermore, supplementation of maturation medium with ALA attenuated the effect of 1% ethanol and significantly increased the blastocyst formation and hatching rate as compared to control and ethanol groups. In addition, the quality of blastocysts produced in ALA+ethanol was improved based on the low number of TUNEL positive cells, the increased expression level of mRNA for pluripotency, and anti-oxidant markers, and decreased expression of apoptotic genes. Conclusion: The current findings demonstrate that ALA can diminish the effect of ethanol, possibly by decreasing the ROS level and increasing Thiolcontent during oocyte maturation. Using the ALA supplement may have implications in protecting oocytes from alcohol toxicity in affected patients.

Aim: In most Muslim societies the daily routine and lifestyle change markedly during the month of Ramadan because of fasting during daylight hours and the altered day and night rituals. These changes could potentially have significant metabolic effects. The aim of this study was to explore the effects of Ramadan fasting and the resultant lifestyle changes on the biochemical profile and oxidative stress markers in healthy adult males.
Material and Method: Forty-two healthy male volunteers following their usual Ramadan fasting routine were included in the study. The following serum variables were measured at the beginning and at the end of the month: triglycerides, total cholesterol, HDL cholesterol, non-HDL cholesterol, albumin, total protein, CRP, uric acid, ischemiamodified albumin (IMA), albumin adjusted-IMA (AAIMA), and thiol/disulfide homeostasis.
Results: Triglycerides, total cholesterol, non-HDL cholesterol, IMA and AAIMA levels were significantly higher on the last day of Ramadan compared to the first day (p<0.05). HDL cholesterol levels were statistically lower on the last day of Ramadan than the first day (p<0.05). However, there were no significant changes in the remaining variables (total albumin, uric acid, CRP, and thiol/disulfide homeostasis parameters).
Discussion: Lifestyle, nutritional, and diurnal rhythm changes during the month of Ramadan may be associated with hormonal and biorhythm alterations which could be responsible for the observed elevations in serum IMA, AAIMA and non–HDL cholesterol levels. However, further studies are required to ascertain the direct causes of these changes.
Keywords: Ramadan Fasting; Oxidative Stress; Ischemia Modified Albumin; Thiol/disulfide Homeostasis; Non-HDL Cholesterol

New data on the chemistry of thiophenethiols have been reviewed systematically. Synthetic routes to these compounds, their reactions with nucleophiles and radicals, and a number of other properties have been examined. The bibliography includes 78 references.