Thiol Form Research Articles

Structural basis of the excitatory amino acid transporter 3 substrate recognition.

Excitatory amino acid transporters (EAATs) reside on cell surfaces and uptake substrates, including L-glutamate, L-aspartate, and D-aspartate, using ion gradients. Among five EAATs, EAAT3 is the only isoform that can efficiently transport L-cysteine, a substrate for glutathione synthesis. Recent work suggests that EAAT3 also transports the oncometabolite R-2-hydroxyglutarate (R-2HG). Here, we examined the structural basis of substrate promiscuity by determining the cryo-EM structures of EAAT3 bound to different substrates. We found that L-cysteine binds to EAAT3 in thiolate form, and EAAT3 recognizes different substrates by fine-tuning local conformations of the coordinating residues. However, using purified human EAAT3, we could not observe R-2HG binding or transport. Imaging of EAAT3 bound to L-cysteine revealed several conformational states, including an outward-facing state with a semi-open gate and a disrupted sodium-binding site. These structures illustrate that the full gate closure, coupled with the binding of the last sodium ion, occurs after substrate binding. Furthermore, we observed that different substrates affect how the transporter distributes between a fully outward-facing conformation and intermediate occluded states on a path to the inward-facing conformation, suggesting that translocation rates are substrate-dependent.

Synthesis, Antimicrobial, DNA Interactions, In Vitro Cytotoxicity, and Cell Cycle Analysis Efficiency of Newly Nano‐Sized Cu (II), Ni (II), Co (II), and Zn (II) Thio‐Schiff Base Complexes of 2‐((E)‐((4,5‐Dimethyl‐2‐(((E)‐4‐Methylbenzylidene)Amino)Phenyl)imino)Methyl)‐Benzenethiol

ABSTRACTNano‐sized bivalent metal complexes, specifically [M(L)2] with L = 2‐((E)‐((4,5‐dimethyl‐2‐(((E)‐4‐methylbenzylidene)amino)phenyl)‐imino)methyl)benzenethiol] (C23H22N2S) and M = Cu (II) (C1), Co (II) (C2), Ni (II) (C3), and Zn (II) (C4), underwent synthesis and subsequent characterization. Elemental analyses, infrared, NMR, mass, electronic, magnetic susceptibility, conductivity assessments, and X‐ray diffraction studies were used to assess our bivalent metal complexes. DFT studies were used to study the tautomeric equilibrium of the tridentate thio‐Schiff base ligand (HL), via the DFT\B3LYP method in connection with a 6–311G* correlation consistent basis set. Two tautomers, which are thione and thiol forms, were studied to estimate the predominant one. The metal formed four coordinated with the tridentate N2S donor thio‐Schiff base to form octahedral geometry complexes. The SEM, TEM, XRD, AFM, and EDX of the studied complexes unveiled distinct and strong diffraction peaks, signifying their crystalline nature and providing evidence of their particle sizes being within the nano‐size. The crystal sizes calculated for all complexes were determined to be ranging from 27.73 to 76.39 nm. The interactions between metal complexes and calf thymus DNA, and their potential for mimicking insulin activity, were investigated in a controlled lab setting by measuring their ability to inhibit alpha‐amylase. The antimicrobial potential of thio‐Schiff base ligand (HL) plus complexes (C1–C4) were tested. The viscosity and UV–Vis absorption determinations were utilized to assess the calf thymus DNA (CT‐DNA) interaction with the nano‐sized metal (II) chelates. Our flow cytometry data indicate significant levels of apoptosis and cell cycle arresting in both liver and breast cancer cell lines.

Probing the Adsorption Sites of 5‐amino‐2‐mercaptobenzimidazole Conformations on Colloidal Gold Nanoparticles Investigated by SERS and DFT

AbstractGold nanoparticles (AuNP) have shown great potential in biomedical applications due to their unique and tunable properties. Understanding the ligand conformation on AuNP has profound interest in nanoparticle research leading to a precise drug delivery system. Colloidal AuNPs were synthesized using trisodium citrate as reducing agent. Normal Raman spectrum (NRS) in solid and aqueous phase identifies that 5‐amino‐2‐mercaptobenzimidazole (5A2MBI) mainly exist as thione form. Surface enhanced Raman scattering (SERS) investigation of 5A2MBI depending on pH was performed to explore the adsorption mechanism of thiolate and thione conformations on AuNPs. Density functional theory (DFT) calculations were used to find the band assignments and molecular electrostatic potential (MEP) mapping to identify the electron rich site where metal can interact preferentially. Using SERS spectral analysis and DFT results, surface adsorption scheme was proposed. At basic pH, 5A2MBI adsorbs on AuNP as thiolate form bidentately via Sulfur and nitrogen atom of imidazole ring with tilted geometry. However, in acidic condition the thione form adsorbs on nanosurface with perpendicular orientation.

Hydrogen-atom tunneling in small thioamides: N-methylthiourea, thiobenzamide and 2-cyanothioacetamide

The most stable thione tautomeric forms of N-methylthiourea, thiobenzamide and 2-cyanothioacetamide were isolated in low-temperature argon matrices. The higher-energy thiol tautomers of these compounds were generated upon irradiation of matrix-isolated monomers with UV (λ > 270 nm) light. For N-methylthiourea and thiobenzamide, kept in the dark at 3.5 K for a long period of time, a spontaneous thiol → thione hydrogen atom tunneling transformation occurred. Only the thiol isomers with the favorably oriented hydrogen atom of the imino group underwent these hydrogen-atom tunneling processes. The other thiol isomers, with the hydrogen atom of the imino group oriented towards the sulfur atom, did not undergo the thiol → thione conversion. For the photogenerated thiol forms of 2-cyanothioacetamide, no spontaneous thiol → thione tautomeric transformation was detected. Instead, only the spontaneous conformational change of one S-H rotamer of the thiol 2-cyanothioacetamide tautomer into the other S-H rotamer was observed.

O-versus S-Metal Coordination of the Thiocarboxylate Group: An NMR Study of the Two Tautomeric Forms of the Ga(III)-Photoxenobactin E Complex.

Photoxenobactin E (1) is a natural product with an unusual thiocarboxylic acid terminus recently isolated from an entomopathogenic bacterium. The biosynthetic gene cluster associated with photoxenobactin E, and other reported derivatives, is very similar to that of piscibactin, the siderophore responsible for the iron uptake among bacteria of the Vibrionaceae family, including potential human pathogens. Here, the reisolation of 1 from the fish pathogen Vibrio anguillarum RV22 cultured under iron deprivation, its ability to chelate Ga(III), and the full NMR spectroscopic characterization of the Ga(III)-photoxenobactin E complex are presented. Our results show that Ga(III)-photoxenobactin E in solution exists in a thiol-thione tautomeric equilibrium, where Ga(III) is coordinated through the sulfur (thiol form) or oxygen (thione form) atoms of the thiocarboxylate group. This report represents the first NMR study of the chemical exchange between the thiol and thione forms associated with thiocarboxylate-Ga(III) coordination, including the kinetics of the interconversion process associated with this tautomeric exchange. These findings show significant implications for ligand design as they illustrate the potential of the thiocarboxylate group as a versatile donor for hard metal ions such as Ga(III).

Incorporating pH into DFT-D+U and microflotation recovery studies on heterocyclic collector-pyrite interactions

This study adopted both computational and experimental approaches to design by modification of 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO) and 2-mercaptobenzimidazole (MBI) heterocyclic collectors by introducing a carbon sulphide (–CS2) group and forming 2-trithiocarbonatebenzothiazole (TTCBT), 2-trithiocarbonatebenzoxazole (TTCBO) and 2-trithiocarbonatebenzomidazole (TTCBI) derivatives collectors. The adsorption behaviour of the heterocyclic collectors (and derivatives) on pyrite and subsequent hydrophobicity at different pH conditions were characterised using molecular modelling and microflotation approaches, respectively. The computational adsorptions were performed on dry and hydrated surfaces in their neutral thiolate and thione (acidic) form on the pyrite (100) surface. It was found that under dry and neutral conditions the TTCBONa and TTCBTNa were more exothermic, while under dry and acidic conditions the TTCBIH was more exothermic followed by MBIH and MBTH. Under hydrated and neutral conditions MBONa was predicted as the most exothermic, while for hydrated and acidic conditions MBTH, TTCBTH and TTCBIH were more exothermic. It was found that under acidic conditions, the heterocyclic collectors were more exothermic than for neutral condition on the hydrated surface. The microflotation at pH = 8 showed that MBO achieved higher recoveries, while at pH = 6 MBT, TTCBT and TTCBI achieved higher recoveries that could reach 90 %. The derivatives under acidic conditions were found to have good recovery performance, which showed that the introduction of a –CS2 group on the exocyclic sulphur atom improved the affinity and therefore hydrophobicity of the mercapto-heterocyclic collectors on the pyrite surface, and thus these derivatives can enhance the flotation of pyrite minerals. In addition, the computational predictions complimented by experimental recoveries are essential to a meaningful development of modelling as a tool in mineral processing reagent design.

Glutathione Reductase Expression and Its Prognostic Significance in Colon Cancer.

Maintaining a balanced redox state within cells is crucial for the sustenance of life. The process involves continuous cytosolic disulfide reduction reactions to restore oxidized proteins to their reduced thiol forms. There are two main cellular antioxidant pathways-the thioredoxin (Trx) and glutathione (GSH)/glutaredoxin (Grx) systems. In the GSH/Grx system, glutathione reductase (GR; GSR) catalyses the reduction of GSH disulfide (GSSG) to its sulfhydryl form (GSH), which can then further reduce oxidized Grxs. GR is an essential enzyme that helps in maintaining the supply of reduced glutathione-GSH, which is a significant reducing thiol found in most cells and known for its antioxidant properties. Therefore, it can have a significant impact on cancer development. To investigate this further, we performed an immunohistochemical analysis of GR protein expression in colon adenocarcinoma samples collected from patients with primary colon adenocarcinoma (stage I and II) and patients with metastasis to regional lymph nodes (stage III). The results of our study revealed a significant relationship between the immunohistochemical expression of GR and tumour histological grade, depth of invasion, regional lymph node involvement, staging, and PCNA immunohistochemical expression. It was found that 95% of patients with stage I had low levels of GR expression, whereas 89% of patients with stage III had high levels of immunohistochemical expression. A high level of expression was also detected in the patients with stage II of the disease, where almost 63% were characterized by a high expression of GR. The Western blot method revealed that the highest level of expression was found in the LS 174T cell line, which corresponds to stage II. The results of our study indicate that the immunohistochemical expression of GR may act as an independent prognostic factor associated with colon adenocarcinoma patients' prognosis.

Riboflavin-based photocatalysis for aerobic oxidative S–N bond formation of thiols and amines

Abstract A novel organophotocatalytic process using riboflavin derivatives, which allows aerobic oxidative multistep S–S, S–N, and S–O bond formations of thiols and amines, is presented herein. The reaction proceeded under mild metal-free conditions using air (1 atm) as an environmentally friendly oxidant, yielding sulfinamides and sulfonamides.

Adsorption of 2-Mercaptobenzothiazole Organic Inhibitor and Its Effects on Copper Anodic Oxidation in Alkaline Environment

2-Mercaptobenzothiazole (2-MBT) is well established as an effective organic corrosion inhibitor for the protection of copper and other metals. The presence of heteroatoms (2 sulphur and 1 nitrogen) in its structure, enables it to bond to the metallic substrate and form a protective barrier layer on the surface which restricts the pathways for the corrosive ions to the metal surface. However, despite numerous works discussing the inhibiting properties on copper, several questions remain, notably regarding the role played by the surface native oxide on the bonding mechanisms, the stability, and the inhibition efficiency of the organic film formed in various environments.In this work, the adsorption of 2-MBT on copper and its effects on anodic oxide growth in a strong alkaline medium (0.1 M NaOH solution) were investigated. Various cathodic pre-treatment methods were applied to modify and control the native oxide-covered Cu surface during the formation of the inhibitor layer. Cyclic voltammetry (CV) tests were performed to determine how the growth of anodic Cu(I) oxide is altered by the 2-MBT organic inhibitor layers pre-adsorbed in different pre-treatment conditions. Additionally, X-ray photoelectron spectroscopy (XPS) and time-of-flight – secondary ion mass spectrometry (ToF-SIMS) were used to investigate the bonding mechanisms of the 2-MBT molecule to the copper surface, including the role of surface native oxides in the formation of the interface with the inhibitor, the effect of increased exposure time to the inhibitor, the stability of the organic inhibitor layer upon anodic polarisation, and the oxide growth upon anodic polarization. The absence of chlorides eliminates their interference in the understanding the oxidation process in a 2-MBT-containing alkaline solution. Additionally, anodic oxidation is studied in the Cu(I) potential range, which allows us to evaluate the effects of 2-MBT on the oxide layer that forms directly on the bare metallic substrate.The results show that 2-MBT significantly impedes the growth of the passivating Cu(I) oxide by forming a multilayered organic film with the inner layer chemisorbed to the surface. A major factor influencing the formation and properties of the organic barrier layer is the presence and structure of the interfacial native oxides on which it forms. The 2-MBT molecules bond to the copper substrate mostly via its sulphur atoms along with a small fraction of the nitrogen atoms also bonding to the metallic substrate. Additionally, there is an interaction between the inhibitor molecules and copper released from the surface to form metal-organic complexes in the outer layers of the thicker films. Longer exposure times to the inhibitor of a surface with negligible oxides increased the efficiency of the organic barrier layer in impeding the growth of anodic oxide.Upon anodic polarisation, the 2-MBT barrier layer grows in thickness, with inclusion of Cu-2-MBT complexes. It is proposed that the thiolate form of 2-MBT, which is the dominant conformer in an alkaline environment, allows for additional bonding possibilities to the Cu atoms and Cu(I) ions of or released from the surface oxide, forming Cu-2-MBT complexes that deposit on the surface and thus increasing the thickness of the organic barrier layer. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Advanced grant agreement No. 741123, CIMNAS).

Adsorption behavior and mechanism of ethyl mercaptan in natural gas on Cu-modified hexaniobate nanotubes

The presence of sulfur compounds in natural gas seriously affects the yield of hydrogen production from natural gas reforming and the lifespan of catalysts. This study aims to clarify the characteristics and mechanism of the removal of ethyl mercaptan (EM) in equilibrium CH4 by Cu-modified hexaniobate nanotubes (Cu-HNT-450), which was synthesized through a method of copper ions exchange-flocculation-calculation. The EM breakthrough adsorption experiments and the valence state of copper and the types of sulfur on Cu-HNT-450 during dynamic tests were investigated. The removal of EM is mainly achieved through the chemical adsorption of CuO, Cu2O and oxygen on Cu-HNT-450. In the process of EM removal, catalytic oxidation, sulfonate formation and reactive adsorption lead to the formation of sulfide, copper sulfonate and copper thiolate, respectively. Cu-HNT-450 has the highest breakthrough adsorption capacity for EM, reaching 103.6 mg/g at 50 °C. The exhausted Cu-HNT-450 can also be regenerated by thermal treatment at different temperatures under nitrogen atmosphere. However, due to the strong chemical adsorption of sulfur containing compounds, the recovery of nitrogen thermal regeneration removal efficiency is limited. This research work provides guidance for the design of mercaptans removal catalysts and deepens the understanding of the reaction mechanism of mercaptans removal.

Understanding Cysteine Reactivity in Protein Environments with Electric Fields.

The role cysteine residues play in proteins is mediated by their protonation state, whereby the thiolate form of the side chain is highly reactive while the thiol form is more inert. However, the pKa of cysteine residues is hard to predict as it can differ widely from its reference value in solution, an effect that is accentuated by local effects in the heterogeneous protein environment. Here, we present a new approach to the prediction of cysteine reactivity based on electric field calculations at the thiol/thiolate group. We validated our approach by predicting the protonation state of cysteine residues in different protein environments (in the active site, at the protein surface, and buried within the protein interior), including Cys-25 in papaya protease omega, which was proven problematic for the more traditional constant pH molecular dynamics (MD) technique. We predict pKa shifts consistent with experimental observations, and the decomposition of the electric fields into contributions from molecular fragments provides a direct handle to rationalize local pH and pKa effects in proteins without introducing parameters other than those of the force field used for MD simulations.

Formation of volatile organic sulfur compounds by low thermal maturation of source rocks: A geochemical proxy for natural gas

Volatile organic sulfur compounds (VOSC) are trace components of natural gas that can provide substantial information regarding gas origins, migration, and key processes such as H2S generation and its occurrence in natural gas reservoirs. In the current study we demonstrate the applicability of VOSC as a proxy for gas-source rock correlations and identification of interactions between H2S and other natural gas components. We studied the molecular and isotopic compositions of VOSC formed during low-level thermal maturation (%Ro equivalent = 0.60–0.71) of six different immature source rocks covering a variety of kerogens (types I, II, II-S and III). Anhydrous pyrolysis experiments (300 °C, 72h) were performed on all the source rocks studied, and the produced gases were analyzed for their molecular compositions and compound specific sulfur isotopes of the various VOSC formed. The formed gases were either dominated by CH4 (32.2–49.9%) or CO2 (31.9–46.2%) and contained a variety of alkanes in the C2–C5 range. H2S formed in 6 out of 8 experiments at concentrations ranging from 0.6 to 4.3%. The results demonstrated formation of VOSC in all experiments, regardless of kerogen types or source rock lithologies. The formation of thiols (16–121.2 ppm) in the produced gas was restricted to those experiments that contained H2S. This indicates that thiols formation is limited to gas-phase interactions between H2S and hydrocarbons. In contrast, thiophenes formed in all experiments (14.9–1778.8 ppm) regardless of H2S presence. Thiols preserved the δ34S signal of their associated H2S due to gas-phase interactions between the two, while thiophenes showed no interaction with the associated H2S and instead preserved the δ34S signature of the bulk kerogen (within 3.5‰ on average) of each source rock. This work demonstrates the applicability of thiophenes to act as a gas-source rock proxy for natural gas and thiols as a proxy for identification of present or paleo-interactions between natural gas and H2S.

Pro-angiogenic effect of a synthetic Cu(II) complex [CuII(L)2] [LH = tautomeric thiolate form of 2-ethoxybenzaldehyde-N(4)-dihexyl-3-thiosemicarbazone

Synthesis and structural characterization of a thiosemicarbazone derivative of Cu(II) [CuII(L)2] [LH = tautomeric thiolate form of 2-ethoxybenzaldehyde-N(4)-dihexyl-3-thiosemicarbazone (L1)] (1) is reported. From the structural characterization data, the metal centre in 1 is found to have in square planar geometry. Both the free ligand (L1) and the metal complex (1) showed pro-angiogenic activity on fertilized chicken eggs. In Chorio-Allantoic Membrane (CAM) assay, L1 was found to promote blood capillary growth by 31.5% in 24 h, whereas for 1 it was 40.0%. In aortic arch assay also, 1 showed better angiogenic potential than the free L1.

Effect of a keratin coupling agent on the mechanical properties of a bovine hair-thermoplastic starch composite

A coupling agent (CA) was obtained through chemical modification of bovine hair. For that purpose, hair waste was treated using two concentrations of potassium hydroxide (KOH), 0.15 and 0.25 N. Treated and untreated hair waste was characterized. Fourier-transform infrared (FTIR) spectra showed that alkali treatment caused the formation of thiols (773 cm−1) and sulfonate groups (1063 cm−1 and 1041 cm−1) as a consequence of disulfide bond breakage. Furthermore, the keratin structure was disorganized (1697 cm−1), and functional groups –NH2 (1574 cm−1) were exposed. The vibrational analysis confirmed S–S bond cleavage to form S–H groups. Thermogravimetric analysis indicated an important disorganization of the keratin molecule. Additionally, differential scanning calorimetry (DSC) analysis corroborated the protein denaturation due to decomposition of the α-helix. Scanning electron microscopy (SEM) showed a clear effect on hair surface integrity, which promotes its interaction with the polymer matrix. Water absorption assays showed that alkaline treatment produces higher absorption due to a greater presence of polar functional groups. With the aim of assessing the CA's ability to act as a compatibilizer in a composite material, it was mixed with thermoplastic cornstarch (TPS) as a polymeric matrix and untreated hair fiber (UHF) as a reinforcing agent. The composites were processed by extrusion and injection molding. Young's modulus, tensile strength, and elongation at break were evaluated, showing higher values for the first two when the percentage of CA was increased.

Each Cellular Compartment Has a Characteristic Protein Reactive Cysteine Ratio Determining Its Sensitivity to Oxidation.

Signaling and detoxification of Reactive Oxygen Species (ROS) are important patho-physiologcal processes. Despite this, we lack comprehensive information on individual cells and cellular structures and functions affected by ROS, which is essential to build quantitative models of the effects of ROS. The thiol groups from cysteines (Cys) in proteins play a major role in redox defense, signaling, and protein function. In this study, we show that the proteins in each subcellular compartment contain a characteristic Cys amount. Using a fluorescent assay for -SH in thiolate form and amino groups in proteins, we show that the thiolate content correlates with ROS sensitivity and signaling properties of each compartment. The highest absolute thiolate concentration was found in the nucleolus, followed by the nucleoplasm and cytoplasm whereas protein thiolate groups per protein showed an inverse pattern. In the nucleoplasm, protein reactive thiols concentrated in SC35 speckles, SMN, and the IBODY that accumulated oxidized RNA. Our findings have important functional consequences, and explain differential sensitivity to ROS.

Nitric oxide delivery and heme-assisted S-nitrosation by the bedbug nitrophorin

Nitrophorins are heme proteins used by blood feeding insects to deliver nitric oxide (NO) to a victim, leading to vasodilation and antiplatelet activity. Cimex lectularius (bedbug) nitrophorin (cNP) accomplishes this with a cysteine ligated ferric (Fe(III)) heme. In the acidic environment of the insect's salivary glands, NO binds tightly to cNP. During a blood meal, cNP-NO is delivered to the feeding site where dilution and increased pH lead to NO release. In a previous study, cNP was shown to not only bind heme, but to also nitrosate the proximal cysteine, leading to Cys-NO (SNO) formation. SNO formation requires oxidation of the proximal cysteine, which was proposed to be metal-assisted through accompanying reduction of ferric heme and formation of Fe(II)-NO. Here, we report the 1.6 Å crystal structure of cNP first chemically reduced and then exposed to NO, and show that Fe(II)-NO is formed but SNO is not, supporting a metal-assisted SNO formation mechanism. Crystallographic and spectroscopic studies of mutated cNP show that steric crowding of the proximal site inhibits SNO formation while a sterically relaxed proximal site enhances SNO formation, providing insight into specificity for this poorly understood modification. Experiments examining the pH dependence for NO implicate direct protonation of the proximal cysteine as the underlying mechanism. At lower pH, thiol heme ligation predominates, leading to a smaller trans effect and 60-fold enhanced NO affinity (Kd = 70 nM). Unexpectedly, we find that thiol formation interferes with SNO formation, suggesting cNP-SNO is unlikely to form in the insect salivary glands.

Synthesis, spectroscopic characterization, molecular studies, and biological evaluation of (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide and some of its transition metal complexes

Novel Ni(II), Cu(II), Zn(II), Cd(II), and Pd(II) complexes (1–6) with (E)-N'-((7-methyl-2-oxo-1,2-dihydroquinolin-3-yl)methylene)morpholine-4-carbothiohydrazide ligand (HL) were prepared and characterized via different analytical and spectroscopic techniques. The spectral data showed that the ligand is bound with copper(II) chloride, zinc(II) chloride, cadmium(II) chloride, and potassium tetrachloropalladate(II) in its neutral thione form in complexes 2, 4, 5, and 6, respectively. Furthermore, the ligand was coordinated with nickel (II) chloride and copper(II) acetate in complexes 1 and 3 as a monobasic tridentate in its thiol form. Thermogravimetric studies were performed for the prepared compounds and the pyrolytic mechanism was proposed for some complexes. DFT, TD-DFT, and NBO calculations were achieved at the B3LYP/LanL2DZ level of theory. Computational studies showed that the investigated compounds have high hyperpolarizability values (β) suggesting their potential use in the creation of non-linear optical materials. Many bacterial and fungal strains were used to assess the ligand and its metal complexes' antibacterial activities. In general, metal complexes have been shown to possess a stronger antibacterial and antifungal effect thanthe free ligand. Complex 5 exhibited respectable antibacterial activity versus Gram-positive bacteria. Furthermore, Zn(II) and Cd(II), complexes 4 and 5 have shown excellent activity against Gram-negative bacteria. Complex 4 exhibited a superior antifungal activity against two types of tested fungi compared with other compounds and standard Ketoconazole. Molecular docking of the ligand and its complexes 1, 2, and 5 were performed against tyrosyl-tRNA synthetase. The more negative values of the binding energy indicate that complexes 1 and 5 have higher inhibition efficiency than the free ligand.

Headspace detection of ethanethiol in wine by cobalt phthalocyanine modified screen-printed carbon electrodes

The formation of thiols has a notable and detrimental sensory impact, especially in the aroma of bottled wines. Their detection in wine is of great interest to avoid important economic and image losses for wineries. This work reports the study of different cobalt phthalocyanine/nanomaterials-based sensors for the headspace detection of volatile thiols. The amperometric procedure based on the use of carbon sensors simply modified with cobalt phthalocyanine showed the best performance. Under the optimum conditions of applied potential, +0.8 V, and pH of the supporting electrolyte, 2.6, this procedure shows a reproducibility of 7% (n = 5) in terms of relative standard deviation of the slopes of calibration curves built in the concentration range from 9.9 to 82.6 μg/L, a capability of detection of 12.5 μg/L and a decision limit of 6.5 μg/L (α = β = 0.05). The use of this electrocatalytic material and the headspace measurements reduce interferents, increasing the selectivity of the procedure, which allows the easy and successful quantification of ethanethiol in white and red wines.

Role of thiols and ascladiol production in patulin degradation by lactobacilli

Patulin is a mycotoxin contaminant in various foods with apple products being its major dietary source. Yeast can reduce patulin levels during fermentation via biotransformation and thiol-adduct formation, with the ability of patulin to react with thiols being well known. Conversion of patulin to ascladiol by lactobacilli has been sparsely reported, while the contribution of thiols in reduction of patulin levels by lactobacilli remains undocumented. In this study, 11 strains of lactobacilli were screened for ascladiol formation in apple juice fermentation. Highest bioconversion was obtained for Lactiplantibacillus plantarum strains followed by Levilactobacillus brevis TMW1.465. Ascladiol production was also detected in several other lactobacilli species albeit in trace amounts. Reduction in patulin levels by Fructilactobacillus sanfranciscensis DMS 20451 and its glutathione reductase (ΔgshR) negative mutant was also assayed to determine the contribution of thiols. The hydrocinnamic acid reductase of Furfurilactobacillus milii did not contribute to reduction of patulin levels. In conclusion, this study demonstrated the potential of various lactobacilli in reduction of patulin levels via biotransformation of patulin to ascladiol, while also providing evidence for the role of thiol formation by lactobacilli and its presence in reducing patulin levels during fermentation.

Green-Light Responsive Perylene Bisimides for Atom-Economic Thiol Generation and Click-Ligation.

Novel methylthiophene/benzo[b]thiophene perylene bisimide thiol-precursors that would generate thiols via a green-light-induced (λexc = 530 nm, φre = 0.33) photorearrangement are presented herein. The "no-wash", photoreleased thiols thus enabled a subsequent thiol-ene click ligation with electron-deficient substrates. Moreover, by virtue of the intrinsic fluorescence evolution from the rearrangement of perylene bisimide scaffolds, the whole process of thiol formation could be self-reported, further potentiating themselves with application versatilities.