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Interspecies hybridization has been shown to be a powerful tool for developing and improving brewing yeast in a number of industry-relevant respects. Thanks to the popularity of heavily hopped ‘India Pale Ale’-style beers, there is an increased demand from brewers for strains that can boost hop aroma. Here, we explored whether hybridization could be used to construct strains with an enhanced ability to release hop-derived flavours through β-lyase activity, which releases desirable volatile thiols. Wild Saccharomyces strains were shown to possess high β-lyase activity compared to brewing strains, however, they also produced phenolic off-flavours (POF) and showed poor attenuation. To overcome these limitations, interspecies hybrids were constructed by crossing pairs of one of three brewing and one of three wild Saccharomyces strains (S. uvarum and S. eubayanus). Hybrids were screened for fermentation ability and β-lyase activity, and selected hybrids showed improved fermentation and formation of both volatile thiols (4MMP, 3MH and 3MH acetate) and aroma-active esters compared to the parent strains. Undesirable traits (e.g. POF) could be removed from the hybrid by sporulation. To conclude, it was possible to boost the release of desirable hop-derived thiols in brewing yeast by hybridization with wild yeast. This allows production of beer with boosted hop aroma with less hops (thus improving sustainability issues).

Aims: DsbA catalyzes disulfide bond formation in secreted and outer membrane proteins in bacteria. In pathogens, DsbA is a major facilitator of virulence constituting a target for antivirulence antimicrobial development. However, many pathogens encode multiple and diverse DsbA enzymes for virulence factor folding during infection. The aim of this study was to determine whether our recently identified inhibitors of Escherichia coli K-12 DsbA can inhibit the diverse DsbA enzymes found in two important human pathogens and attenuate their virulence. Results: DsbA inhibitors from two chemical classes (phenylthiophene and phenoxyphenyl derivatives) inhibited the virulence of uropathogenic E. coli and Salmonella enterica serovar Typhimurium, encoding two and three diverse DsbA homologues, respectively. Inhibitors blocked the virulence of dsbA null mutants complemented with structurally diverse DsbL and SrgA, suggesting that they were not selective for prototypical DsbA. Structural characterization of DsbA-inhibitor complexes showed that compounds from each class bind in a similar region of the hydrophobic groove adjacent to the Cys30-Pro31-His32-Cys33 (CPHC) active site. Modeling of DsbL- and SrgA-inhibitor interactions showed that these accessory enzymes could accommodate the inhibitors in their different hydrophobic grooves, supporting our in vivo findings. Further, we identified highly conserved residues surrounding the active site for 20 diverse bacterial DsbA enzymes, which could be exploited in developing inhibitors with a broad spectrum of activity. Innovation and Conclusion: We have developed tools to analyze the specificity of DsbA inhibitors in bacterial pathogens encoding multiple DsbA enzymes. This work demonstrates that DsbA inhibitors can be developed to target diverse homologues found in bacteria. Antioxid. Redox Signal. 29, 653–666.

Proteins are modified during milk processing and storage, with sidechain oxidation and crosslinking being major consequences. Despite the prevalence and importance of proteins in milk, and particularly caseins (∼80% of total content), the nature of the cross-links formed by oxidation, and their mechanisms of formation, are poorly characterized. In this study, we investigated the formation and stability of cross-links generated by the nucleophilic addition of Cys residues to quinones generated on oxidation of Tyr residues. The mechanisms and stability of these adducts was explored using ubiquitin as a model protein, and β-casein. Ubiquitin and β-casein were oxidized using a rose Bengal/visible light/O2 system, or by the enzyme tyrosinase. The oxidized proteins were incubated with glutathione or β-lactoglobulin (non-oxidized, but unfolded by treatment at 70 °C), before analysis by SDS-PAGE, immunoblotting and LC-MS. Our data indicate that Cys-quinone adducts are readily-formed, and are stable for >48 h. Thus, oxidized β-casein reacts efficiently with the thermally unfolded β-lactoglobulin, likely via Michael addition of the exposed Cys to a Tyr-derived quinone. These data provide a novel, and possibly general, mechanism of protein cross-link formation, and provides information of the stability of these species that have potential as markers of protein quality.

Forisomes are giant polyprotein complexes that undergo reversible conformational rearrangements from a spindle-like to a plug-like state in response to Ca2+ or changes in pH. They act as valves in the plant vasculature, and reproduce this function in vitro to regulate flow in microfluidic capillaries controlled by electro-titration. Heterologous expression in yeast or plants allows the large-scale production of tailor-made artificial forisomes for technical applications. Here we investigated the unexpected disintegration of artificial forisomes in response to Ca2+ following the deletion of the M1 motif in the MtSEO-F1 protein or the replacement of all four conserved cysteine residues therein. This phenomenon could be mimicked in wild-type forisomes under reducing conditions by adding a thiol alkylating agent. We propose a model in which reversible changes in forisome structure depend on cysteine residues with ambiguous redox states, allowing the formation of intermolecular disulfide bridges (confirmed by mass spectrometry) as well as noncovalent thiol interactions to connect forisome substructures in the dispersed state. This is facilitated by the projection of the M1 motif from the MtSEO-F1 protein as part of an extended loop. Our findings support the rational engineering of disintegrating forisomes to control the release of peptides or enzymes in microfluidic systems.

Aims: Influenza A virus hemagglutinin (HA) binding to sialic acid on lung epithelial cells triggers membrane fusion and infection. Host thiol isomerases have been shown to play a role in influenza ...

An efficient TBAI-catalyzed ring-opening sulfonylation of benzo[d]thiazole and arylsulfonyl hydrazide has been developed. Various benzo[d]thiazole as good thiol surrogates are compatible with the catalytic conditions, providing diversified unsymmetrical thiosulfonates with good yields. This strategy features mild reaction conditions, broad substrate scope, readily available starting materials, and gram-scale synthesis. Importantly, these products can be readily converted to novel o-amino-substituted diaryl sulfides.

Production of H2 by methanol reforming is of particular interest due the low cost, ready availability, and high hydrogen content of methanol. However, most current methods either require very high temperatures and pressures or strongly rely on the utilization of large amounts of base. Here we report an efficient, base-free aqueous-phase reforming of methanol homogeneously catalyzed by an acridine-based ruthenium pincer complex, the activity of which was unexpectedly improved by a catalytic amount of a thiol additive. The reactivity of this system is enhanced by nearly 2 orders of magnitude upon addition of the thiol, and it can maintain activity for over 3 weeks, achieving a total H2 turnover number of over 130 000. On the basis of both experimental and computational studies, a mechanism is proposed which involves outer-sphere dehydrogenations promoted by a unique ruthenium complex with thiolate as an assisting ligand. The current system overcomes the need for added base in homogeneous methanol reforming and also highlights the unprecedented acceleration of catalytic activity of metal complexes achieved by the addition of a catalytic amount of thiol.

Adenostemma lavenia (L.) Kuntze (Asteraceae) is widely distributed in tropical regions of East Asia, and both A. lavenia and A. madurense (DC) are distributed in Japan. In China and Taiwan, A. lavenia is used as a folk medicine for treating lung congestion, pneumonia, and hepatitis. However, neither phylogenic nor biochemical analysis of this plants has been performed to date. We have reported that the aqueous extract of Japanese A. lavenia contained high levels of ent-11α-hydroxy-15-oxo-kaur-16-en-19-oic acid (11αOH-KA; a kaurenoic acid), which is a potent anti-melanogenic compound. Comparison of chloroplast DNA sequences suggested that A. lavenia is originated from A. madurense. Analyses of kaurenoic acids revealed that Japanese A. lavenia and A. madurense contained high levels of 11αOH-KA and moderate levels of 11α,15OH-KA, while Taiwanese A. lavenia mainly contained 9,11αOH-KA. The diverse biological activities (downregulation of Tyr, tyrosinase, gene expression [anti-melanogenic] and iNOS, inducible nitric oxide synthase, gene expression [anti-inflammatory], and upregulation of HO-1, heme-oxygenase, gene expression [anti-oxidative]) were associated with 11αOH-KA and 9,11αOH-KA but not with 11α,15OH-KA. Additionally, 11αOH-KA and 9,11αOH-KA decreased Keap1 (Kelch-like ECH-associated protein 1) protein levels, which was accompanied by upregulation of protein level and transcriptional activity of Nrf2 (NF-E2-related factor-2) followed by HO-1 gene expression. 11αOH-KA and 9,11αOH-KA differ from 11α,15OH-KA in terms of the presence of a ketone (αβ-unsaturated carbonyl group, a thiol modulator) at the 15th position; therefore, thiol moieties on the target proteins, including Keap1, may be important for the biological activities of 11αOH-KA and 9,11αOH-KA and A. lavenia extract.

Adenosylhopane is a crucial precursor of C35 hopanoids, which are believed to modulate the fluidity and permeability of bacterial cell membranes. Adenosylhopane is formed by a crosslinking reaction between diploptene and a 5'-deoxyadenosyl radical that is generated by the radical S-adenosyl-L-methionine (SAM) enzyme HpnH. We previously showed that HpnH from Streptomyces coelicolor A3(2) (ScHpnH) converts diploptene to (22R)-adenosylhopane. However, the mechanism of the stereoselective C-C bond formation was unclear. Thus, here, we performed biochemical and mutational analysis of another HpnH, from the ethanol-producing bacterium Zymomonas mobilis (ZmHpnH). Similar to ScHpnH, wild-type ZmHpnH afforded (22R)-adenosylhopane. Conserved cysteine and tyrosine residues were suggested as possible hydrogen sources to quench the putative radical reaction intermediate. A Cys106Ala mutant of ZmHpnH had one-fortieth the activity of the wild-type enzyme and yielded both (22R)- and (22S)-adenosylhopane along with some related byproducts. Radical trapping experiments with a spin-trapping agent supported the generation of a radical intermediate in the ZmHpnH-catalyzed reaction. We propose that the thiol of Cys106 stereoselectively reduces the radical intermediate generated at the C22 position by the addition of the 5'-deoxadenosyl radical to diploptene, to complete the reaction.

Razuprotafib, a sulphamic acid-containing phosphatase inhibitor, is shown in vivo to undergo enzymatic oxidation and methylation to form a major metabolite in monkey and human excreta with an m/z- value of 633.LC-MS/MS analysis of samples derived from incubations of razuprotafib with human liver microsomes and recombinant CYP2C8 enzyme has elucidated the metabolic pathway for formation of the thiol precursor to the S-methyl metabolite MS633 (m/z- 633).Under in vitro conditions, the major pathway of razuprotafib metabolism involves extensive oxidation of the thiophene and phenyl rings.A single oxidation takes place at one of the phenyl groups. Multiple oxidations occur at the thiophene moiety: initial oxidation results in the formation of a thiolactone followed by a second oxidation giving rise to an S-oxide of the thiolactone, which is further metabolised to the ring-opened form and ultimate formation of a thiol (m/z- 619).An additional mono-oxidation pathway involves epoxidation of the thiophene followed by hydrolysis to a diol.The thiol and diol metabolites are trapped by the addition of a nucleophilic trapping agent, 3-methoxyphenacyl bromide (MPB), giving adducts with m/z- 767.The thiol is a likely precursor to the major in vivo razuprotafib metabolite, MS633.

Methylglyoxal (MGO) is a reactive byproduct formed by several metabolic precursors, the most notable being triosephosphates in glycolysis. While many MGO-mediated adducts have been described, the reactivity and specific biomolecular targets of MGO remain incompletely mapped. Based on our recent discovery that MGO can form stable mercaptomethylimidazole crosslinks between cysteine and arginine (MICA) in proteins, we hypothesized that MGO may participate in myriad reactions with biologically relevant guanidines and thiols in proteins, metabolites, and perhaps other biomolecules. Herein, we performed steady-state and kinetic analyses of MGO reactivity with several model thiols, guanidines, and biguanide drugs to establish the plausible and prevalent adducts formed by MGO in proteins, peptides, and abundant cellular metabolites. We identified several novel, stable MICA metabolites that form in vitro and in cells, as well as a novel intermolecular post-translational MICA modification of surface cysteines in proteins. These data confirm that kinetic trapping of free MGO by thiols occurs rapidly and can decrease formation of more stable imidazolone (MG-H1) arginine adducts. However, reversible hemithioacetal adducts can go on to form stable MICA modifications in an inter- and intramolecular fashion with abundant or proximal guanidines, respectively. Finally, we discovered that intracellular MICA-glutathione metabolites are recognized and exported by the efflux pump MRP1, providing a parallel and perhaps complementary pathway for MGO detoxification working alongside the glyoxalase pathway. These data provide new insights into the plausible reactions involving MGO in cells and tissues, as well as several new molecular species in proteins and metabolites for further study.

Objective: In this study, we aimed to evaluate the relationship between thiol-disulfide homoeostasis and hemogram parameters in COVID-19 patients. Methods: Total thiol(TT), Native thiol(NT), dynamic disulfide status(DDS), DDS/NT, DDS/TT, NT/TT ratio and CBC parameters were analyzed in 68 patients with positive COVID-19 and 31 healthy individuals. Results: TT, NT, DD, hemoglobin and hematocrit levels were higher in the control group than in patient groups. TT, NT, DD and lymphocyte levels of COVID-19 patients treated in medical floor were higher than those treated in intensive care unit; WBC, neutrophil and NLR were low(P

A 200 KDa acid-stable thiol β-amylase, appreciably present in the stem of Paederia foetida (48,000 ± 5,500 Units (U)/100 g fresh wt.) was purified by (NH4)2SO4 precipitation, ion exchange chromatog...

Generally, volatile thiols are hard to be measured with electrospray-ionization-type LC-MS due to the volatility. Therefore, we here evaluated the pretreatment of their S-bimanyl derivatization by monobromobimane to enable the detection as nonvolatile derivative. Consequently, we successfully developed the convenient and efficient method through the quantitative analysis of 2-furanmethanethiol (volatile thiol odorant of coffee aroma) in coffee bean.

The tellurium oxyanion tellurate is toxic to living organisms even at low concentrations; however, its mechanism of toxicity is poorly understood. Here, we show that exposure of Escherichia coli K-12 to tellurate results in reduction to elemental tellurium (Te[0]) and the formation of intracellular reactive oxygen species (ROS). Toxicity assays performed with E. coli indicated that pre-oxidation of the intracellular thiol pools increases cellular resistance to tellurate-suggesting that intracellular thiols are important in tellurate toxicity. X-ray absorption spectroscopy experiments demonstrated that cysteine reduces tellurate to elemental tellurium. This redox reaction was found to generate superoxide anions. These results indicate that tellurate reduction to Te(0) by cysteine is a source of ROS in the cytoplasm of tellurate-exposed cells.

Alcohol use disorder (AUD) is the loss of a person's quality of life due to increased alcohol consumption and the failure of alcohol consumption control. In this study, the intra- and extracellular thiol-disulfide levels in people with AUD were compared with age-matched healthy controls. Forty male patients diagnosed with AUD and thirty healthy male individuals were included in the study. In addition to psychiatric and sociodemographic tests routine biochemical evaluations have been performed. The alcohol group had significantly higher Michigan Alcohol Screening Test (MAST), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI) scores compared to the control group. While there was a decrease in the intracellular GSH and extracellular native thiol levels in the blood of the alcohol group, GSSG and disulfide levels were increased, respectively. Subsequently, while there was an increase in the intracellular GSSG/GSH content levels in the alcohol group compared to the control group, the ratios of GSH/GSH+GSSG were decreased. These changes, indicative of oxidative stress, were observed both in blood serum and erythrocytes. Also, there was an increase in alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT) mean corpuscular volume (MCV), C-reactive protein (CRP) levels in the alcohol group in routine biochemical tests, while total protein, folic acid, ferritin and hemoglobin (HGB) levels were decreased. Our results suggest that increased intra- and extracellular GSSG/GSH % (disulfide/native thiol %) may serve as an indicator of developing oxidative stress in individuals with AUD.

In the present study, different derivatives of thymol (1) viz. hydrazide (2), oxadiazole thiol (3), triazole thione (4), hydrazones (5-7), and β-lactams (8-10) were synthesized. All synthesized compounds were identified and characterized using elemental analysis, UV-Visible, 1H NMR, 13C NMR, and IR spectroscopic techniques. Synthesized thymol derivatives were evaluated for antifungal potential against phytopathogenic fungi Fusarium moniliforme, Rhizoctonia solani, and Dreschlera maydis of maize in comparison to recommended standards in terms of percent inhibition and ED50 values. Thymol was more effective as compared to its derivatives against all three tested fungi. Hydrazones (5-7) and β-lactams (8-10), having m-NO2 substituted phenyl ring (6, 9), were less effective as compared to o-NO2 and p-NO2 analogs against F. moniliforme and R. solani, however, the reverse trend was observed against D. maydis. Thymol and its derivatives were also tested for insecticidal activity against stored grain (chickpea) insect Callosobruchus chinensis and various parameters viz. egg laying, adult emergence, and grain damage were recorded and compared. Compounds having oxadiazole thiol (3) and triazole thione (4) moiety showed promising effects against insect C. chinensis.

During metabolism, carboxylic acids are often activated by conjugation to the thiol of coenzyme A (CoA). The resulting acyl-CoAs comprise a group of ∼100 thioester-containing metabolites that could modify protein behavior through non-enzymatic N-acylation of lysine residues. However, the importance of many potential acyl modifications remains unclear because antibody-based methods to detect them are unavailable and the in vivo concentrations of their respective acyl-CoAs are poorly characterized. Here, we develop cysteine-triphenylphosphonium (CysTPP), a mass spectrometry probe that uses "native chemical ligation" to sensitively detect the major acyl-CoAs present in vivo through irreversible modification of its amine via a thioester intermediate. Using CysTPP, we show that longer-chain (C13-C22) acyl-CoAs often constitute ∼60% of the acyl-CoA pool in rat tissues. These hydrophobic longer-chain fatty acyl-CoAs have the potential to non-enzymatically modify protein residues.

The health of living systems depends on the proper balance of cellular oxidative and reductive processes (redox balance), which is reflected in the thiol-disulfide balance in cells. Glutathione is the predominant low-molecular-weight thiol in mammalian cells. Through its diverse actions as an antioxidant, as a detoxifier of xenobiotics, and as a regulator of protein function, among others, glutathione is vitally important to cell health. Spectroscopic probes that can act as sensors or reporters of glutathione are, therefore, useful. We report here the synthesis of three new disulfide-linked dinitroxides, whose EPR spectra change dramatically upon reaction with glutathione, and the characterization of the kinetics of their reaction with glutathione.

Unsymmetrical disulfides have been effectively prepared through thiol exchange with symmetrical disulfides employing a simple PdCl2/DMSO catalytic system. The given method features excellent functional group tolerance, a broad substrate scope, and operational simplicity. This reaction is especially useful for late-stage functionalization of bioactive scaffolds such as peptides and pharmaceuticals. Disulfide-containing organic dyes have also been prepared. This transformation could be extended to thiol-diselenide or thiol-ditelluride exchange affording RS-SeR' or RS-TeR'.

Thiol-disulphide homeostasis (TDH) is a new parameter indicating oxidative stress that plays a role in the pathogenesis of various clinical disorders. Our study planned to investigate TDH in COVID-19 patients. Age and gender-matched healthy subjects (n = 70) and COVID-19 patients (n = 144) were included in the study. In addition to the routine laboratory parameters of the groups, their native thiol (NT), total thiol (TT) and disulphide levels were measured. Primarily, we compared COVID-19 patients to the healthy control group for inflammatory parameters, NT, TT and disulphide levels. Then, COVID-19 patients were divided into two groups according to the severity of the disease as mild to moderate and severe COVID-19, and the three groups were compared with each other. Predictive value of thiol parameters in the diagnosis of COVID-19 and in the determining its severity, and its correlation with presence and duration of symptoms were investigated. Severe COVID-19 patients had lower NT and TT levels compared with healthy controls and mild to moderate patients (P < 0.001 for both). The results of ROC analysis show that the greatest AUC was IL-6 and NT (AUC = 0.97, AUC = 0.96, respectively) between control and COVID-19 patients, while it was CRP and NT (AUC = 0.85, AUC = 0.83) between mild to moderate and severe patients. A negative correlation was found between duration of symptoms of dyspnoea, cough, fever, and sore throat and NT (r = −0.45, P = 0.017, r = −0.418, P < 0.001, r = −0.131, P = 0.084, r = −0.452, P = 0.040, respectively). NT and TT levels have a strong predictive value in the diagnosis of COVID-19 and in determining disease severity. Our results support that changing TDH parameters appears to have an important role in disease pathogenesis and it can be used in clinical management of patients., Graphical abstract Image 1

Glycoclusters with high glycan density accessible through grouping of monosaccharide units in multimeric forms are important due to their high affinity and capability in recognition with protein re...

MoO2Cl2/MoOCl4 have been reacted with 4-phenylimidazole-2-thiol/6-mercaptopurine monohydrate/2-mercaptopyridine in acetonitrile solvent in unimolar/bimolar proportions at room temperature. The products thus obtained are: MoOCl3(C9H8N2S), [1]; Mo2O3Cl6(C9H7N2S)(CH3CN)2, [2]; Mo2O3Cl8(C9H7N2S)2(CH3CN)2, [3] and Mo2O4Cl4(C5H4NS-SN4C5), [4]. These products were studied by various techniques: infrared, proton NMR, liquid/gas chromatography-mass spectrometry, elemental analyses. Owing to the sensitivity of the products to air and moisture, the reactions and work ups were performed in vacuum line purged with oxygen by flushing dry nitrogen in it. Ions observed in mass spectrum are concurrent with the depicted formulae.

Covalent modifications of thiol and amine groups may control the function of proteins involved in the regulatory and signaling pathways of the cell. In this study, we developed a simple cysteamine assay which can be used to study the reactivity of electrophilic compounds towards primary amine and thiol groups in an aqueous environment. The detection principle is based on the electrochemical, photometrical and mass spectrometric analyses of cysteamine (2-aminoethanethiol) as the molecular probe. This technique is useful for studying the reaction kinetics of electrophiles with thiol (SH) and amino (NH2) groups. The decrease in analytical responses of cysteamine was monitored to evaluate the reactivity of three electrophilic activators of the Nrf2 pathway, which mediates the cellular stress response. The SH-reactivity under cell-free conditions of the tested electrophiles decreased in the following order: 4-hydroxy-2-nonenal ≥ nitro-oleic acid > sulforaphane. However, as shown in RAW264.7 cells, the tested compounds activated Nrf2-dependent gene expression in the opposite order: sulforaphane > nitro-oleic acid ≥ 4-hydroxy-2-nonenal. Although other factors in addition to chemical reactivity play a role in biological systems, we conclude that this cysteamine assay is a useful tool for screening potentially bioactive electrophiles and for studying their reactivity at a molecular level.

Cysteine oxidation is important in cellular redox regulation, signaling, and biocatalysis. To understand the biological relevance of cysteine oxidation, it is desirable to identify the proteins involved, the site of the oxidized cysteine, and the relevant oxidation states. Because the thiol of cysteine can be converted to a wide range of oxidation states, mapping these oxidative modifications is challenging. The dynamic and reversible nature of many cysteine oxidation states compounds the difficulty in such proteomic analyses. In this review, we examine methods to detect cysteine sulfenic acid — a particularly challenging functional group to analyze because of its reactive nature. We focus on the selectivity of recently reported probes and discuss some challenges and opportunities in this field.

The thiol redox proteome refers to all proteins whose cysteine thiols are subjected to various redox-dependent posttranslational modifications (PTMs) including S-glutathionylation (SSG), S-nitrosylation (SNO), S-sulfenylation (SOH), and S-sulfhydration (SSH). These modifications can impact various aspects of protein function such as activity, binding, conformation, localization, and interactions with other molecules. To identify novel redox proteins in signaling and regulation, it is highly desirable to have robust redox proteomics methods that can provide global, site-specific, and stoichiometric quantification of redox PTMs. Mass spectrometry (MS)-based redox proteomics has emerged as the primary platform for broad characterization of thiol PTMs in cells and tissues. Herein, we review recent advances in MS-based redox proteomics approaches for quantitative profiling of redox PTMs at physiological or oxidative stress conditions and highlight some recent applications. Considering the relative maturity of available methods, emphasis will be on two types of modifications: 1) total oxidation (i.e., all reversible thiol modifications), the level of which represents the overall redox state, and 2) S-glutathionylation, a major form of reversible thiol oxidation. We also discuss the significance of stoichiometric measurements of thiol PTMs as well as future perspectives toward a better understanding of cellular redox regulatory networks in cells and tissues.

We have recently found that penicillamine, a classic copper-chelating thiol-drug for Wilson's disease, can delay tetrachlorohydroquinone (TCHQ) autooxidation via a previously unrecognized redox-activity. However, its underlying molecular mechanism remains not fully understood. In this study, we found, interestingly and unexpectedly, that superoxide dismutase (SOD) can significantly shorten the delay of TCHQ autooxidation by penicillamine, but not by ascorbate; SOD can also markedly increase the yields of the oxidized form of penicillamine. Similar effects were observed with a recently-developed specific and sensitive superoxide anion radical (O2•-) probe CT-02H, which was also employed to successfully measure O2•- generated from both TCHQ and TCHQ/penicillamine systems for the first time. More importantly, addition of extra O2•- (KO2/18-crown-6) can further prolong the delaying effects by penicillamine and slow down penicillamine consumption. Taken together, an unexpected critical role of O2•- in TCHQ/penicillamine interaction was proposed: O2•- may regenerate penicillamine, thereby continuously reducing TCSQ•- to TCHQ and finally delaying TCHQ autooxidation; In contrast, if O2•- were eliminated, which can not only markedly change the reaction equilibrium, accelerate the rate of interaction, and ultimately shorten the delay of TCHQ autooxidation by penicillamine, but can also accelerate penicillamine oxidation to form its corresponding disulfide solely via redox reaction without any minor nucleophilic reaction. These findings not only further support our previously-proposed redox mechanism for the protection against TCHQ-induced cytotoxicity by penicillamine, but also reveal a new mode of action for O2•- in the inhibition of haloquinoids-induced toxicity by thiol antioxidants.

Monohydroboration of substituted 1,3-diynes with an N-heterocyclic carbene borane (NHC-borane) occurs under radical conditions using an azo initiator, such as ACCN and AIBN, and a thiol as a polarity-reversal catalyst. The reaction is highly regio- and stereoselective and provides stable NHC-(E)-alkynylalkenylboranes.

Secondary metabolites from medicinal plants have been reported to inhibit the formation of glucose-induced protein aggregation. This study investigated the inhibitory potential of Vernonia amygdalina leaf extracts on amyloid protein aggregation. Prevention of glycation-induced amyloid-beta fibril formation was evaluated through the assessment of anti-glycation capacities of the extracts, inhibitions of glycation-induced oxidation of protein thiol groups and protein aggregation. Colorimetric methods were used for the estimation of aqueous and methanol extract of V. amygdalina. Luteolin, luteolin-7-O-β-glucuronoside, and luteolin-7-O-β-glucoside were identified through a previous study and evaluated for their binding energies with amyloid-beta and amyloid-beta fibril. The results showed that aqueous extract had higher amounts of phenolics while methanol extract had higher amounts of flavonoids contents. The aqueous extract exhibited higher albumin glycation inhibitory potential with the IC50 value of 65 µg/ml. The methanol extract possessed higher protective effects on the total thiol groups of the glycated albumin and also exhibited higher inhibition of aggregates formation when compared with the aqueous extract. Luteolin-7-O-β-glucuronoside had the highest binding affinity with the amyloid beta-peptide (1-42) and amyloid-beta (1-42) fibrils with the mean values of − 5.63 kcal/mol and −6.48 kcal/mol respectively. However, it was observed that luteolin exhibited the highest binding free energy of − 20.43 kcal/mol and − 8.67 kcal/mol with both proteins respectively. The ADMET properties revealed all the phytochemicals possess drug-like properties. These results demonstrated that phytoconstituents of V. amygdalina could act as highly potent inhibitors of protein aggregation and could be a promising candidate for the management of hyperglycaemia-induced protein aggregation.

A photochemical thiol addition/aerobic oxidation cascade reaction has been developed. This protocol enables efficient oxidative coupling of epoxides and thiols to access structurally valuable β-hydroxylsulfoxides. A broad range of functional groups are compatible to obtain moderate to good yields of the target products. Mechanistic studies revealed a sequential reaction pathway involving base-promoted thiol addition of thiols to epoxides and visible-light-induced aerobic oxygenation of thioethers.

A new UV and visible light photoinitiator, quinizarin derivative 6,11-dimethoxy-7,10-dihydrotetracene-5,12-dione (Q4), was synthesized and characterized. Its photophysical properties were evaluated by various spectroscopic and computational methods. Q4 demonstrates excellent initiating efficiency for free-radical, thiol–ene, cationic and hybrid photopolymerizations. While free-radical and thiol–ene photopolymerizations can be initiated without any additives, the corresponding cationic and hybrid polymerizations still require oxidants such as iodonium salts.

Cysteine persulfide (CysSSH) and polysulfides (CysS[S] n H, n>1) are cysteine derivatives having sulfane sulfur atoms bound to cysteine thiol. Recent advances in the development of analytical methods for detection and quantification of persulfides and polysulfides have revealed the biological presence, in both prokaryotes and eukaryotes, of persulfide/polysulfide in diverse forms such as CysSSH, glutathione persulfide and protein persulfides. Accumulating evidence has suggested that persulfide/polysulfide species may involve in a variety of biological events such as biosyntheses of sulfur-containing molecules, tRNA modification, regulation of redox-dependent signal transduction, mitochondrial energy metabolism via sulfur respiration, cytoprotection from oxidative stress via their antioxidant activities, and anti-inflammation against Toll-like receptor-mediated inflammatory responses. Development of chemical sulfur donors may facilitate further understanding of physiological and pathophysiological roles of persulfide/polysulfide species, including regulatory roles of these species in immune responses.

Nitric oxide (NO) binds to soluble guanylyl cyclase (GC1) and stimulates its catalytic activity to produce cGMP. Despite the key role of the NO-cGMP signaling in cardiovascular physiology, the mechanisms of GC1 activation remain ill-defined. It is believed that conserved cysteines (Cys) in GC1 modulate the enzyme's activity through thiol-redox modifications. We previously showed that GC1 activity is modulated via mixed-disulfide bond by protein disulfide isomerase and thioredoxin 1. Herein we investigated the novel concept that NO-stimulated GC1 activity is mediated by thiol/disulfide switches and aimed to map the specific Cys that are involved. First, we showed that the dithiol reducing agent Tris (2-carboxyethyl)-phosphine reduces GC1 response to NO, indicating the significance of Cys oxidation in NO activation. Second, using dibromobimane, which fluoresces when crosslinking two vicinal Cys thiols, we demonstrated decreased fluorescence in NO-stimulated GC1 compared to unstimulated conditions. This suggested that NO-stimulated GC1 contained more bound Cys, potentially disulfide bonds. Third, to identify NO-regulated Cys oxidation using mass spectrometry, we compared the redox status of all Cys identified in tryptic peptides, among which, ten were oxidized and two were reduced in NO-stimulated GC1. Fourth, we resorted to computational modeling to narrow down the Cys candidates potentially involved in disulfide bond and identified Cys489 and Cys571. Fifth, our mutational studies showed that Cys489 and Cys571 were involved in GC1'response to NO, potentially as a thiol/disulfide switch. These findings imply that specific GC1 Cys sensitivity to redox environment is critical for NO signaling in cardiovascular physiology.

Thiol-functionalized degradable polyesters have significant applications in nanoscience and polymer chemistry due to the combination of the biodegradability and biocompatibility of polyesters and the special chemical and physical properties of thiols. It is challenging to synthesize thiol-functionalized polyesters via ring-opening polymerization by using unprotected mercapto-alcohol as an initiator because both hydroxyl and thiol have the ability to initiate the polymerization. Since 2005, the protecting-group-free synthetic strategy has been reported based on chemoselective catalysis and microflow technology. In this review, non-metal and metal catalytic unprotected mercapto-alcohol initiating ring-opening polymerization is summarized in order. The advantages of using flow chemistry are highlighted. The remaining challenges and opportunities are discussed for the development of thiol-polymer synthesis and applications.

Objectives Synthetic biology has emerged from molecular biology and engineering approaches and aims to develop novel, biologically-inspired systems for industrial and basic research applications ranging from biocomputing to drug production. Surprisingly, redoxin (thioredoxin, glutaredoxin, peroxiredoxin) and other thiol-based redox systems have not been widely utilized in many of these synthetic biology applications. Methods We reviewed thiol-based redox systems and the development of synthetic biology applications that have used thiol-dependent parts. Results The development of circuits to facilitate cytoplasmic disulfide bonding, biocomputing and the treatment of intestinal bowel disease are amongst the applications that have used thiol-based parts. We propose that genetically encoded redox sensors, thiol-based biomaterials and intracellular hydrogen peroxide generators may also be valuable components for synthetic biology applications. Discussion Thiol-based systems play multiple roles in cellular redox metabolism, antioxidant defense and signaling and could therefore offer a vast and diverse portfolio of components, parts and devices for synthetic biology applications. However, factors limiting the adoption of redoxin systems for synthetic biology applications include the orthogonality of thiol-based components, limitations in the methods to characterize thiol-based systems and an incomplete understanding of the design principles of these systems.

Although the nanoparticles (NP) are seemed to have the immense potentiality for using in different biomedical fields the possible toxic health effects of these NPs associated with human exposure is a serious concern. In general, the toxicity of gold nanoparticles (AuNPs) depends on their physical dimensions and surface chemistry. In the present study, size-specific AuNPs were used to test its potential harmful effect in the biochemical and histological alterations of liver tissue in experimental animals (swiss albino mice). Animals were exposed to the AuNPs for seven days. Oxidative stress in whole tissue homogenates and in mitochondrial extracts and histological studies were studied in the liver. Significant deterioration in glutathione reductase (GR), malondialdehyde (MDA), and total thiol content were observed in the case of whole liver tissue homogenates; on the other hand, in case of whole-brain tissue homogenates, deterioration in glutathione S-transferase (GST), total thiol and MDA was observed. Almost all the lipid peroxidation product and oxidative stress marker enzymes were affected in the hepatic system were observed in AuNP treated animals. Anatomical differences in liver tissue were also observed in the AuNP treated animals. Minute loss of hepatic cords, occurrence of swallowing and atrophic cells is the major detoriation observed in AuNP treated animals. Surface negativity and the small size of the AuNPs may be assumed to affect the biochemical and cellular architecture of the organs. The further molecular level analysis will reveal the usability potential of AuNP in the body system for different purposes.

The replacement of disulfide bridges with metabolically stable isosteres is a promising strategy to improve the stability of disulfide-rich polypeptides towards reducing agents and isomerases. A diaminodiacid-based strategy is one of the most effective methods to construct disulfide bond mimics, but modified diaminodiacids have not been developed till now. Inspired by the fact that alkylation of disulfide bonds can regulate the activity of polypeptides, herein, we report the first example of thioether bridged diaminodiacids incorporating Cys Cβ dimethyl modification, obtained by penicillamine (Pen)-based thiol alkylation. The utility of these new diaminodiacids was demonstrated by the synthesis of disulfide surrogates of oxytocin containing a short-span disulfide bond and of KIIIA with large-span disulfide bonds. This new type of synthetic bridge further extends the diaminodiacid toolbox to facilitate the study of the structure–activity relationship of disulfide-rich peptides.

Primary Sjögren's syndrome (pSS) is a disease associated with the overexpression of proinflammatory cytokines, and oxidative stress is one of the factors responsible for its etiopathogenesis. This study aimed to investigate the thiol/disulphide homeostasis in pSS patients.The study included 68 pSS patients and 69 healthy controls. Thiol/disulphide homeostasis (total thiol, native thiol, and disulphide levels) was measured using the automatic spectrophotometric method developed by Erel and Neselioglu, and the results of the 2 groups were compared.The gender and age distributions of the pSS and control groups were similar (It was concluded that the thiol/disulphide balance shifted towards disulphide in patients with pSS.Primarni Sjögrenov sindrom (pSS) je bolest povezana sa prekomernom ekspresijom proinflamatornih citokina, dok je oksidativni stres jedan od faktora odgovornih za njegovu etiopatogenezu. Cilj ove studije je bio da ispita tioldisulfidnu homeostazu kod pacijenata sa pSS-om.Studija je obuhvatila 68 pacijenata sa pSS-om i 69 zdravih kontrolnih pojedinaca. Homeostaza tiol-disulfida (nivoi ukupnog tiola, nativnog tiola i disulfida) je izmerena pomoću automatske spektrofotometrijske metode koju su razvili Erel i Neselioglu. Rezultati dve grupe su upoređeni.Raspodela po polu i starosti pacijenata sa pSSom i pojedinaca u kontrolnoj grupi je bila slična (Zaključeno je da se ravnoteža tiol/disulfid pomera prema disulfidu kod pacijenata sa pSS-om.