Fe(NO_3)_3·9H_2O/Fe(HSO_4)_3:An efficient reagent system for the oxidation of alcohols,thiols and sulfides in the absence of solvent

Fe（NO3）3-9H2O/Fe（HSO4）3 was used as an efficient reagent system for the oxidation of alcohols to their corresponding carbonyl compounds. All reactions were performed in the absence of solvent in good to high yields. Under the same reaction conditions, thiols and sulfides were also converted to their corresponding disulfides and sulfoxides, respectively. 2007 Farhad Shirini. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A Mechanism Study of a Novel Acid-Activatable Michael-Type Fluorescent Probe for Thiols

A Michael addition is usually taken as a base-catalysed reaction. However, our synthesized 2-（quinolin-2-ylmethylene） malonic acid （QMA） as a Michael-type thiol fluorescent probe is acid-active in its sensing reaction. In this work, based on theoretic calculation and experimental study on 7-hydroxy-2-（quinolin-2-ylmethylene） malonic acid, we demonstrated that QMA as a Michael acceptor is acid-activatable, i.e., it works only in solutions at pH〈7, and the lower the pH of solutions is, the higher reactivity QMA has. In alkaline solution, the malonate QMA[-2H＋]2- cannot react with both RSand RSH. In contrast, 2-（quinolin-2- ylmethylene） malonic ester （QME）, the ester of QMA, reveal a contrary pH effect on its sensing reaction, that is, it can sense thiols in alkaline solutions but not in acidic solutions, like a normal base-catalysed Michael addition. The values of activation enthalpies from theoretic calculation support the above sensing behavior of two probes under different pH conditions. In acidic solutions, the protonated QMA is more highly reactive towards electrophilic attack over its other ionized states in neutral and alkaline solutions, and so can react with lowly reactive RSH. In contrast, there is a big energy barrier in the interaction of QME with RSH （acidic solutions）, and the reaction of QME with the highly reactive nucleophile RS- is a low activation energy process （in alkaline solutions）. Theoretic calculation reveals that the sensing reaction of QMA undergoes a 1,4-addition process with neutral thiols （RSH）, and a 1,2-addition pathway for the sensing reaction of QME with RS-. Therefore, the sensing reaction of QMA is an acid-catalysed Michael addition via a 1,4-addition, and a normal base-catalysed Michael addition via a 1,2-addition.

Glutathione peroxidase mimicry of diphenyl diselenide: Plausible contribution of proteins’ thiols

Organoseleniums are a class of compounds attracting attention across the globe owing to their Glutathione peroxidase(GPx)mimicry,which confers on them a strong antioxidant activity.Diphenyl diselenide(DPDS)is an Organoselenium whose GPx mimetic property has been suggested to rely on the oxidation of non-protein or protein thiols critical to the activities of some sulfhydryl enzymes.This study,therefore investigated the GPx mimic/antioxidant property of DPDS as well as the role of thiols of two key sulfhydryl enzymes,cerebral Na^(+)/K^(+)-ATPase(sodium pump)and hepatic delta-aminolevulinic acid dehydratase(δ-ALAD)in the GPx mimicry of DPDS.Albino Wistar rats were euthanized,and the liver and brain were removed and used to assay for the effect of DPDS on lipid peroxidation induced by two prooxidants[Fe2^(+)(10μM)and H2O2,(1 mM)]as well as the activities of the sulfhydryl enzymes.The results revealed that DPDS profoundly(P<0.05)counteracted Fe2^(+)and H2O2-induced lipid peroxidation in the rats’hepatic and cerebral tissues.Furthermore,the results of assay systems for lipid peroxidation and sodium pump revealed that DPDS inhibited Na^(+)/K^(+)-ATPase and lipid peroxidation in the brain tissue homogenates in the same reaction system.A similar result was obtained in the assay system for lipid peroxidation and hepaticδ-ALAD as DPDS simultaneously inhibited the enzyme’s activity and lipid peroxidation.This suggests that the GPx mimetic property of DPDS may be linked to the enzymes’loss of activity,which further validates the suggestions that the enzymes’inhibition,as well as the antioxidant action of DPDS,rely on the oxidation of critical thiols of the enzymes.However,the GPx mimicry of DPDS should be investigated in the presence of thiol-blocking or oxidizing agents in biological systems in order to further ascertain the role of protein thiols.

Immobilizing Triphenylamine with Photoredox Inert Sr^(2+)Forming Sr-MOF with Controlled Electron Migration for Photocatalytic Oxidation of Thiols to Disulfides

The photocatalytic oxidative coupling of thiols is one of the most popular methods to synthesize the disulfides.Triphenylamine and its derivatives(TPAs)are promising for the above reaction,but suffer from the easy polymerization and difficult separation.To overcome these obstacles while controlling the photogenerated electrons transfer directly to target substrates,herein,we constructed one TPA-based metal-organic framework(MOF),(Me_(2)NH_(2))[Sr(TCBPA)]·DMA·3H_(2)O(1),by direct self-assembly of tris(4′-carboxybiphenyl)amine(H_(3)TCBPA)and photoredox inert strontium ion(Sr^(2+)).DFT calculations revealed that the valence band maximum(VBM)and the conduction band minimum(CBM)are mainly located on TCBPA^(3-),successfully inhibiting the undesirable electron migration to metal nodes.Experimental results indicated that 1 displays superior performance than homogeneous H_(3)TCBPA,which may result from the abundant π…π and C—H…π interactions between the well-arranged TCBPA^(3-)and the build-in electric field between the anionic framework and the Me_(2)NH^(2+).This work highlights that immobilizing TPAs into MOFs is one promising approach to designing heterogeneous photocatalysts for the synthesis of disulfides by oxidative coupling of thiols.

Small molecule fluorescent probes of protein vicinal dithiols

The vicinal dithiol motif is widely present in proteins, and is critical for proteins’ structures and functions.In recent years, a variety of fluorescent probes with high specificity and outstanding optical properties for sensing protein vicinal dithiols have been developed. In this review, we summarized the fluorescent probes of protein vicinal dithiols in literature. These probes are classified into four types based on their acceptor sites, i.e., biarsenical probes, monoarsenical probes, dimaleimide probes and diacrylate probes.Through analyzing the properties of different probes, we expect that this review would help readers further understand the structural factors of these probes and provide the design strategy for novel fluorescent probes with improved properties.

An efficient and convenient method for the preparation of disulfides from thiols using oxygen as oxidant catalyzed by tert-butyl nitrite

An efficient and convenient tert-butyl nitrite-catalyzed selective aerobic oxidation of thiols has been developed. Under the optimal reaction conditions, a number of thiol derivatives including aromatic thiols, heteroaromatic thiols and aliphatic thiols can be converted into their corresponding disulfides in good to excellent yields.

DNA template-synthesized silver nanoparticles:A new platform for high-performance fluorescent biosensing of biothiols

To develop the high-performance fluorescent bio-sensors, the metal nanoparticles were employed as nanoquenchers and at- tracted reasonable attention in the design of fluorescent biosensors. In this work, silver nanoparticles （AgNPs） were obtained via reduction of Ag＋ on FAM-labeled DNA template. For the tight binding between AgNPs and DNA, the tem- plate-synthesized AgNPs turned out high quenching efficiency and could be applied as super nanoquenchers to establish the biosensing platform for fluorescent detection. As an example, the template-synthesized DNA-AgNPs conjugates were em- ployed in sensing thiols. By forming S-Ag bonds, thiols interact intensely with AgNPs and replace the FAM-labeled DNA off from the surface of AgNPs, resulting in a fluorescence enhancement. Besides the advantages of lower background and higher signal-to-background ratio （S/B）, the conjugates present better stability, making them applicable in complicated biological fluids. To further evidence the feasibility of sensing thiols in real samples, the thiols in human urine were detected. The total amount of free thiols found in human urine was ranging from 229 μM to 302μM with the proposed sensor. To conclude the reliability, low content of Cys was added and the recovery was 98%-103%.

A Mild, General, Metal-Free Method for Desulfurization of Thiols and Disulfides Induced by Visible-Light

A visible-light-induced metal-free desulfurization method for thiols and disulfides has been explored.This radical desulfurization features mild conditions,robustness,and excellent functionality compatibility.It was successfully applied not only to the desulfurization of small molecules,but also to peptides.

Chemical interactions between silver nanoparticles and thiols: a comparison of mercaptohexanol against cysteine

The interaction between citrate capped silver nanoparticles and two different thiols, mercaptohexanol （MH） and cysteine, was investigated. The thiols interacted with silver nanoparticles in a significantly contrasting manner. With MH, a sparingly soluble silver（1） thiolate complex AgSRm （Rm = -（CH2）6OH） was formed on the silver nanoparticle surface. Cyclic voltammograms and UV-vis spectra were used to infer that the AgSRm complex on the nanoparticle surface undergoes a phase transition to give a mixture of AgSRm and Ag2S-like complexes. In contrast, when silver nanoparticles were exposed to cysteine, the citrate cap- ping agent on the silver nanoparticles was replaced by cysteine to give cysteine capped nanoparticles. As cysteine capped nanoparticles form, the electrochemical data displayed a decrease in oxidative peak charge but the UV-vis spectra showed a constant signal. Therefore, cysteine capped nanoparticles were suggested to have either inactivated the silver surface or else pro- moted detachment from the electrode surface.

Pyridine-N-oxide： An Efficient Organocatalyst for Ring- Opening Reactions of Aziridines with Aryl Thiols

Pyridine-N-oxide serves as an efficient catalyst for the ring-opening reactions of N-tosylaziridines with various aryl thiols under mild conditions. This transformation is highly effective, which gives rise to the corresponding β-amino sulfides in good to excellent yields.

Target-activated and ratiometric photochromic probe for “double-check” detection of toxic thiols in live cells

Photochromic molecules can achieve reversible isomerization upon alternate light irradiations, which offers a great opportunity to improve the precision of analytes detection and imaging in complicated biological environments. Previous reported photochromic probe exhibited only mono-color switching and an initially fluorescence-ON state that may cause high background signal and impose an adverse impact on the desired sensing precision. To overcome this set-back, we developed a novel photochromic probe with an analyte-activation mode for ratiometric sensing of toxic thiols in both real water samples and live cells. The dynamic dual-fluorescence signal is released only after the fast and selective cleavage of the 2,4-dinitrophenyl sulfonate by the targeted thiophenol derivatives. Consequently, a "double-check" with synchronized dual-fluorescence blinking for analyte detection is successfully employed upon alternate light triggers with rapid response(k=7.2×10^(-2) s^(-1)), high sensitivity(LOD=6.1 nM) as well as selectivity of thiophenol derivatives over other common thiol species(e.g., GSH, Cys and Hcy). The photochromic probe was successfully introduced to the fast and on-site detection of highly toxic thiophenols in real waste water samples. Moreover, by using confocal laser-scanning microscopy(CLSM) and flow cytometric analysis, the potential applications of this ratiometric photochromic probe for trace toxic thiol sensing in live cells are examined.

Cationic Micelle-catalyzed Ring-Opening Reactions of Aziridines with Thiols in Water

An efficient and practical method is described for the ring-opening reactions of N-tosylaziridines with various thiols in water under mild conditions. Various surfactants have been evaluated to optimize the reactions. Under optimal conditions, these reactions gave rise to the corresponding β-amino sulfides in good to excellent yields.

Two-thiols-regulated fabrication of plasmonic nanoparticles with co-enhanced Raman scattering and circular dichroism responses

Plasmonicnanoparticles(PNPs)with stable nanogaps are important to achieve strong,uniform and quantitative gap-enhanced Raman scattering(GERS)signals.Chiral PNPs with plasmonic circular dichroism(PCD)responses have been discovered to be suitable for applications in enantiomeric recognition,cancer therapy and activation of immune system.Herein,two-thiolsmodulated growth was demonstrated to result in the acquisition of PNPs with synergistically enhanced GERS and PCD signals.4-Aminothiophenol(4-ATP)and cysteine(Cys)played the role of Raman reporter and chiral stimulus,respectively.At a fixed 4-ATP concentration,the GERS signal of PNPs was significantly enhanced with the increase of the concentration of Cys.Simultaneously,at a fixed concentration of Cys,an increase in PCD response was observed by elevating the concentration of 4-ATP.Both aforementioned molecules acted as morphology controllers,leading to the formation of helical shell.It is suggested that the giant GERS and PCD response were contributed by the‘‘hot spots''within the PNPs and more perfect helical shells.Our research pointed out a novel synthetic guideline to obtain PNPs with multiple functionalities by incorporating multi-ligands into the growth stages.

Electrochemically mediated three-component synthesis of isothioureas using thiols as sulfur source

The simultaneous binding/dissociation of multiple bonds in a one-pot manner by multicomponent reactions provide an important approach for developing novel and sustainable pathway in the drug discovery process.Herein we develop an electrocatalytic three-component reaction to construct multifunctional and valuable isothiourea compounds,which uses thiols,isocyanides and amines as substrates.Compared with the previous work,the organic electrosynthesis technique can avoid the requirement of heavy metal catalysts and stoichiometric oxidants.In addition,using thiol as a substrate to participate in the three-component reaction broadens the source of sulfur,which can also construct more abundant isothiourea derivatives.

Assessment of oxidative stress in chronic pancreatitis patients

AIM: To assess the levels of antioxidant capacity and oxidative damage in blood of chronic pancreatitis (CP) patients in comparison with those in healthy control sub- jects, by using several different analytical techniques. METHODS: Thirty-five CP patients and 35 healthy con- trol subjects were investigated prospectively with re- spect to plasma levels of thiols, ferric reducing ability of plasma (FRAP, i.e. antioxidant capacity), levels of protein carbonyls and thiobarbituric acid reactive substances (TBARS). Additionally, we evaluated the production of reactive oxygen species (ROS) in whole blood. RESULTS: The antioxidative thiols including cysteine, cysteinylglycine and glutathione were significantly lower in CP patients. In addition, the non-enzymatic antioxi- dant capacity was significantly lower in CP patients, which correlated with the amount of oxidative protein (protein carbonyls) and the extent of lipid damage (TBARS), both were significantly higher in CP patients. The ROS production in whole blood after stimulation with phorbol 12-myritate 13-acetaat, demonstrated a strong tendency to produce more ROS in CP patients. CONCLUSION: Oxidative stress may contribute to the pathogenesis of chronic pancreatitis by decreasing anti- oxidant capacity and increasing oxidative damage in CP patients may be a rationale for intervention with antioxi- dant therapy.

新型芳基硫醇的合成及在聚芳醚砜紫外交联中的应用

通过假高稀反应和芳香亲核取代反应成功制备了一种新型芳基三硫醇,其与烯丙基聚醚砜(c-PAES)的混合体系在光引发剂TPO的作用下能极大地增强聚醚砜体系的紫外交联速度.研究结果表明,按官能团摩尔比1∶1的比例添加芳基三硫醇的聚醚砜体系在紫外交联情况下,其最终双键转化率提高了1倍左右,而且体系的光反应速率有了极大的提高.交联后聚合物的玻璃化转变温度(Tg)升高了约20℃,并有较好的热稳定性,可作为耐高温材料使用.

Studies on the Thiol Components of Isolated Nuclei

The thiol components of the nonhistone proteins prepared from isolated nuclei from rat liver, regenerating liver and hepatoma 223 cells have been investigated after reaction with radio labelled N-ethylmaleimide and 5-5’-dithiobis-(2-nitrobenzoic acid) (DTNB). The labelled adducts formed were examined by isoelectric focusing analysis in polyacrylamide gel and the distribution of the radiolabels within sliced portions of the gels determined. In the case of the 14C labelled NEM adduct the label was found to be spread amongst numerous protein components within the gel however, in the case of the 35S labelled DTNB adducts, only a small proportion of the label was found in the protein material which was retained in the acidic isoelectric point (pI) region of the gel. The bulk of the 35S labelled adduct (56% - 60%) was found to have migrated into the anode solution (10 mM phosphoric acid). This could be adsorbed onto a hydrophobic resin (XAD2) resin and eluted with methanol. Gel filtration chromatographic analysis of this adduct material on BioGel P2, (exclusion limit 1500 daltons) showed low molecular weight components to be present. Slightly different patterns were obtained for these nuclei, each containing several 35S components with molecular weights greater than the Ellman reagent itself. These 35S labelled thiol components did not contain any protein, peptide or amino acid components indicating strongly that a novel species of thiols could be present in these nuclei bound within the non-histone protein matrices.

Investigation of the Low Molecular Weight Thiol Composition in a Metastatic Prostate Cancer Cell Line (LNCaP) by LC-UV-MS and NMR after Labelling with the Ellman Reagent

The low molecular weight thiols present in the deproteinized extract of a prostate cancer cell line (LNCaP-FGC) were analysed after derivatization with the Ellman reagent (ESSE). The mixed disulphides formed (RSSE) were fractionated, characterized and quantified by liquid chromatography on a C-18 column using UV detection. This revealed the presence, in femtomoles per cell, of glutathione (8.30 ± 0.73), cysteine (2.71 ± 0.04) and cysteinylglycine (0.83 ± 0.10), accounting for the bulk of the thiol present. Further analysis of the cell extracts using a novel and sensitive mass spectrometry technique allowed the detection of low level of an additional derivative which was identified as cysteinylglycerate using NMRspectroscopy.

Stress Ameliorative Effects of Indole Acetic Acid on Hordeum vulgare L. Seedlings Subjected to Zinc Toxicity

The heavy metals present in the environment accumulate in the plants and affect their productivity and yield.By entering the food chain,metals cause several serious health problems in human beings as well as in other organisms.Indole acetic acid(IAA)is known to act as a signaling molecule between symbiotic association of metal accumulating plants and plant growth promoting rhizobacteria(PGPR).Present study demonstrated a protective role of IAA against surplus Zinc(Zn)-induced toxicity to Hordeum vulgare seedlings.Elevated Zn concentrations suppressed the plant growth,caused a reduction in leaf relative water contents(RWC)and elevated free proline and non-protein thiols(NPT)accumulation.Zinc treatment also led to enhanced lipid peroxidation(MDA contents)as well as the activity of ascorbate peroxidase(APX),showing the involvement of antioxidative defense mechanism to reduce Zn induced toxicity.IAA oxidase activity was also observed to increase due to Zn treatment.IAA pretreatment of H.vulgare caryopsis could partly revert the Zn-induced toxicity in seedlings.

Pb-Stress Induced Oxidative Stress Caused Alterations in Antioxidant Efficacy in Two Groundnut (<i>Arachis hypogaea</i>L.) Cultivars

Lead (Pb) is an important environmental pollutant extremely toxic to plants and other living organisms including humans. To assess Pb phytotoxicity, a pot culture experiment was carried out using two groundnut cultivars (Arachis hypogaea L. cultivar K6 and cultivar K9) on plant growth, ROS levels, lipid peroxidation, and antioxidant metabolism using biochemical, histochemical methods. Plants were grown in pots for 14 days, in the botanic garden, and subjected to Pb-stress (0, 100, 200, 400 and 800 ppm) by adding Pb (NO3)2 solution and further allowed to grow for 10 days. The results showed that cultivar K6 registered lower Pb accumulation than cultivar K9, however, localization of Pb was greater in roots than leaves in both groundnut cultivars. The Pb-stress results in an increase in free radicals (O2?- and H2O2) generation in both groundnut cultivars, but more significantly in cultivar K9 than K6. Pb-stress also caused significant changes in the rate of peroxidation as shown in the levels of malondialdehyde (MDA) content in roots and leaves of both groundnut cultivars. Free proline, ascorbic acid (AsA) and non-protein thiol (NP-SH) contents were increased in cultivar K6 due to Pb-stress, but less in cultivar K9. Pb treated plants showed increased levels of antioxidant enzymes such as superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) glutathione reductase (GR) and glutathione S-transferase (GST). Isozyme band intensities of SOD, GPX and APX were more consistent with the respective changes in antioxidative enzyme activities. These results indicate that cultivar K6 possesses greater tolerance potential for Pb toxicity than cultivar K9.