Disulfide Compounds Research Articles

DFT METHOD STUDY ON LUBRICANT PROPERTIES OF DISULFIDE COMPOUNDS AS EXTREME PRESSURE ADDITIVE

The molecular geometries optimization and electronic structures of fourteen disulfide compounds had been investigated by density functional theory (DFT) at 6-31G basis set level. The active atoms and active bonds of tribochemical reaction were obtained according to frontier molecular orbital theory, and the interaction energy of chemical adsorption between disulfides and metal surfaces were calculated. The structure-property relationship had been discussed with satisfactory results. The calculated results indicated that the S–S bond and C–S bond of compounds are trended to be broken when organic disulfide compounds interact with a metal, and the order of anti-wear properties for disulfide compounds: diphenyldisulfide >dibenzyldisulfide >di-n-dodecyldisulfide >di-n-octyldisulfide >di-n-butyldisulfide >diethyldisulfide, the extreme pressure properties of DBDS is superior to that of DPDS. The predicted results based on quantum chemical calculations are in excellent agreement with friction and wear test results.

N-nitrosamine inhibition by strawberry, garlic, kale, and the effects of nitrite-scavenging and N-nitrosamine formation by functional compounds in strawberry and garlic

High nitrate and amine-rich food intake may result in an increased risk of endogenous formation of carcinogenic N-nitroso compounds (NOCs). We studied the effects of whole strawberries, garlic and kale on the formation of N-nitrosodimethylamine (NDMA) in a traditional Korean diet (amine and nitrate-rich) in simulated saliva and gastric conditions. The addition of whole strawberries, kale and garlic juices in the diet reduced NDMA formation by amine and nitrate. Strawberries and garlic juice were more effective than kale. To identify active compound, isolated fractions were prepared from strawberries or garlic juice samples by preparative liquid chromatography. Inhibition of NDMA formation and nitrite-scavenging ability of each fraction (strawberries: S1–S4; garlic juice: A1–A5) was tested. Fraction A4 inhibited NDMA formation by 50.5 ± 5.4% and increased the effect of nitrite-scavenging by 72.3 ± 8.7%. Fractions A3 and A4 were identified as 1,2-benzendicarboxy acid (A3) and S-oxodially disulfide (A4) compounds by mass spectrophotometry and 13C nuclear magnetic resonance.

Synthesis, redox properties, and molecular structure of 4,5-diethylthio-4-cyclopenten-1,3-dione: Cyclic voltammetric evidence for a kinetically stable radical anion

The preparation of the new disulfide compound 4,5-diethylthio-4-cyclopenten-l,3-dione (1) from 4,5-dichloro- 4-cyclopenten-l,3-dione and ethanethiol is described. The title compound has been isolated and characterized in solution by IR and NMR spectroscopies, and the solid-state structure solved by X-ray crystallography. 4,5-Diethylthio-4-cyclopenten-l,3-dione crystallizes in the triclinic space group P-l, a = 7.230(4) A, b = 8.191(5) A, c = 10.187(6) A, α = 108.48(1)°, β = 97.75(1)°, γ = 105.90(1)°, V = 533.8(6) A3, Z = 2, and d calc = 1.346 Mg/m3; R = 0.0406, R w = 0.0967 for 1394 reflections with I > 2σ(I). The redox properties of 4,5-diethylthio-4-cyclopenten-l,3-dione have been examined by cyclic voltammetry in CH2C12 solution, where a reversible one-electron reduction was found. The reduction behavior of the diethylthio derivative is discussed relative to the closely related 4,5-bis(p-tolylthio)-4-cyclopenten-l,3-dione, whose radical anion exhibits quasi-reversible reduction behavior due to competitive C(dione ring)–S bond cleavage. The differences in the electrochemical behavior of the two disulfides are discussed with respect to the ancillary R group.

Suppression of laser-induced choroidal neovascularization by oral administration of SA3443 in mice

The effect of a synthetic cyclic disulfide compound, SA3443, on neovascularization was investigated. In vitro, enzyme-linked immunosorbent assay and RT-PCR demonstrated that SA3443 suppressed the expression of the hypoxia-induced vascular endothelial growth factor (VEGF) at both protein and mRNA levels in ARPE-19 cells. In vivo, the administration of SA3443 to mice with laser-induced choroidal neovascularization (CNV) suppressed the leakage from the lesions and reduced their size. Furthermore, the expression level of VEGF protein was significantly reduced by the administration of SA3443. Taken together, our results demonstrate that SA3443 suppresses VEGF production and reduces vascular leakage and the growth of mouse experimental CNV.

Structural features of some Schiff base disulfide compounds

Structural features of some Schiff base disulfide compounds

Preparation of poly( N-methylpyrrole) modified with pentathiepin rings and its application to positive active material for lithium secondary

Lithium secondary batteries with high energy density are key devices for portable electrical equipments. The specific capacity of metal oxide-based positive active materials is considerably lower than that of lithium metal. Organosulfur compounds, such as disulfide compounds are useful as a positive active material for lithium secondary cells. We prepared modified poly( N-methylpyrrole) (PMPy) with pentathiepin rings (S-PMPy) from PMPy and disulfur dichloride at room temperature. The S-PMPy electrode showed electrochemical responses in the organic electrolyte solution (mixture of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) (1:1, v/v) containing 1 mol dm −3 LiClO 4). The maximum capacity of the test lithium secondary cell with the S-PMPy electrode was 14.8 A h kg −1 (per kilogram of S-PMPy) and the average capacity was 11.5 A h kg −1 (10 cycles) under the constant charge–discharge current condition at room temperature.

Enantioselective Synthesis of Thiosulfinates and of Acyclic Alkylidenemethylene Sulfide Sulfoxides

AbstractEnantioselectivities up to 75 % have been found in the catalytic mono‐oxidation of di‐tert‐butyl disulfide and related compounds as well as of ketene‐S,S‐acetals with an in situ generated chiral dioxirane. The effect of solvents on the enantiomeric excess has also been examined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

The collagenase inhibitor from human polymorphonuclear leukocytes. Isolation, purification and characterisation.

A new collagenase inhibitor of latent human polymorphonuclear collagenase, initially reported by Macartney and Tschesche [Hoppe-Seyler's Z. Physiol. Chem. 361, 298–299 (1980) and FEBS Lett. 119, 327–332 (1980)], has been purified to apparent homogeneity. We described several methods of purification of this inhibitor, but the fastest and most reproducible method is by passage of purified latent human polymorphonuclear leukocyte collagenase on activated thiol-Sepharose 4-B (preceding paper in this journal). Active collagenase is eluted from the column and the collagenase inhibitor is retarded. Elution of the inhibitor is achieved by eluting the column with thiol compounds in the equilibration buffer. Further purification of the inhibitor is obtained by gel filtration on Sephacryl S-300 and ion-exchange chromatography on DEAE-Sephacel. The inhibitor exhibits a strict specificity for mammalian collagenases. It inhibits collagenases isolated from human synovial fluid, human normal and diabetic skin fibroblasts and human embryonic skin fibroblasts. The inactive complexes are all subject to activation by several disulfide compounds, such as oxidised glutathione by the thiol/disulfide interchange reaction already described. The purified inhibitor was shown by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (10% gel) to be homogeneous and displayed an apparent molecular weight of 24500. Titration of the inhibitor with Ellmans reagent revealed that it contains one free sulfhydryl group, a prerequisite for its inhibitory activity. The inhibitor inhibits human polymorphonuclear leukocyte collagenase in a strict 1:1 stoichiometric reaction. The amino acid composition of the complex formed from the inhibitor and active enzyme reproduces that of the latent collagenase thus confirming that the latent enzyme is a 1:1 complex. The inhibitor is an acidic protein having an isoelectric point at pH 5.5, which would be expected from the amino acid analysis. The composition reveals a glycoprotein of about 240 residues containing a carbohydrate moiety composed of N-acetylglucosamine, mannose, galactose and glucose. The amino acid composition of the inhibitor is not identical to that of β1-anticollagenase from human plasma.

Kinetic study of the reaction of carbon disulfide and basic compounds

The reaction of carbon disulfide and basic compounds, including potassium hydroxide (KOH), tetrabutylammonium hydroxide (QOH), and tertiary amine (TBA ), to form CS2-X in a homogeneous solution was studied. A UV detector was used to measure these reactions. The concentration of the active intermediate CS2-X (X: basic compounds), which was not purified from the solution, was measured using a UV instrument. It is found that the reactions did not follow a pseudo first order rate law when potassium hydroxide or tetrabutylammonium hydroxide was used as the basic compound. Nevertheless, a pseudo first order rate law is proposed to describe the kinetics of reactions involving carbon disulfide and tertiary amine. In the reaction of carbon disulfide and tertiary amine, the rate constant of the forward reaction (k1) was obtained through UV absorbance of the product. The effects of organic solvents, temperature, and the concentration of the reactants on the rates of reactions were investigated.

Carbon source-dependent regulation of a second gene encoding glutaredoxin from the fission yeast Schizosaccharomyces pombe

Glutaredoxin (Grx), also known as thioltransferase (TTase), is an enzyme that catalyzes the reduction of a variety of disulfide compounds, including protein disulfides, in the presence of reduced glutathione. A second gene encoding Grx (Grx2) was cloned from the chromosomal DNA of the fission yeast Schizosaccharomyces pombe. The determined DNA sequence contains 1645 bp which is able to encode a polypeptide of 110 amino acids with a molecular mass of 12.2 kDa. The genomic DNA consists of 4 exons and 3 introns. The isolated gene was found to produce functional glutaredoxin that could accelerate the growth of the fission yeast, and is highly expressed at the mid- and late exponential phases. Aluminum, cadmium and hydrogen peroxide marginally enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene. Shifts to lower concentrations (0.2, 0.4 or 0.8%) of D-glucose significantly enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene. And shifts to sucrose (0.2, 0.4, 0.8 or 1.6%) as a sole carbon source markedly enhanced the synthesis of beta-galactosidase from the Grx2-lacZ fusion gene, the degree of which was inversely dependent on concentration. However, nonfermentable carbon sources reduced the expression of the Grx2 gene due to their growth arrest. The transcription factor Pap1 is not involved in the basal expression and induction of the Grx2 gene. The Grx2 protein was subcellularly localized in the nucleus of the yeast cells. Our results indicate that the Grx2 protein, located in the nucleus, is linked with the yeast growth, and that the gene is regulated by carbon sources.

Alkyl‐ or Arylthiolation of Aryl Iodide via Cleavage of the S—S Bond of Disulfide Compound by Nickel Catalyst and Zinc.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Application of the time-resolved spectroscopy on the photo-dissociation dynamics of disulfide compounds in supercritical fluids

Photo-dissociation dynamics of two disulfide compounds [bis( p-aminophenyl) disulfide (BADS) and bis( p-dimethylaminophenyl) disulfide (BDMADS)] in supercritical carbon dioxide and trifluoromethane were studied by transient absorption spectroscopy. For bis( p-aminophenyl) disulfide in carbon dioxide, we found that the absorption bandshape of the p-aminophenylthiyl (APT) radical generated by the photo-dissociation shows an asymmetrical change with a time constant of about 40 ps, as was reported in the case of nonpolar solvents (Y. Hirata, Y. Niga, S. Makita, T. Okada, J. Phys. Chem. A. 101 (1997) 561). For (bis( p-dimethylaminophenyl) disulfide in carbon dioxide, we did not observe an evident change of the absorption bandshape of the p-dimethylaminophenylthiyl radical. On the other hand, we found that the absorption peak position of the radical in trifluoromethane shows a red-shift in the initial 40 ps. The bandshape change and the peak shift were discussed in terms of the radical pair dynamics and the solvation dynamics.

New sulfur derivatives of 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one. Demonstration of regioselective thiolate addition and X-ray diffraction structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one

The reaction of thiols with the heterocyclic compound 2,3-dichloropyrrolo[1,2-a] benzimidazol-1-one (1) has been investigated as a route to new redox-active, bidentate sulfur ligands. Treatment of 1 with either methylthiol or benzylthiol in the presence of pyridine affords monosulfide compounds 2-chloro-3-methylthiopyrrolo[1,2-a] benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3) and the disulfide derivatives 2,3-di(methylthio)pyrrolo[1,2-a]benzimidazol-1-one (4) and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one (5). The substitution of the first chlorine group in 2,3-dichloropyrrolo[1,2-a]benzimidazol-1-one (1) occurs regioselectively at C-3 to produce 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one (2) and 2-chloro-3-benzylthiopyrrolo[1,2-a]benzimidazol-1-one (3), followed by replacement of the remaining chlorine group to furnish the disulfide compounds 4 and 5. The new thiols have been isolated by column chromatography and characterized in solution by spectroscopic methods. The molecular structures of 2-chloro-3-methylthiopyrrolo[1,2-a]benzimidazol-1-one and 2,3-di(benzylthio)pyrrolo[1,2-a]benzimidazol-1-one have been determined by X-ray crystallography. Compound 2 crystallizes as two independent molecules in the monoclinic space group P21/c, a = 13.221(2) A, b = 18.478(2) A, c = 8.948(1) A, β = 100.088(3)°, V = 2152.3(5) A3, Z = 8, and dcalc = 1.547 Mg/m3; R = 0.0354, Rw = 0.0739 for 2820 reflections with I > 2σ(I). Compound 5 crystallizes in the triclinic space group P-1, a = 5.180(1) A, b = 11.494(2) A, c = 17.243(3) A, α = 86.024(3)°, β = 88.606(4)°, γ = 81.235(3)°, V = 1012.1(4) A3, Z = 2, and dcalc = 1.360 Mg/m3; R = 0.0354, Rw = 0.0692 for 2655 reflections with I > 2σ(I). The redox properties of the disulfide compounds 4 and 5 have been explored by cyclic voltammetry, where a one-electron reduction at ca. −1.10 V has been observed for each compound. The site of electron accession in has been established by carrying out molecular orbital calculations at the extended Huuckel level on the model compound 2,3-di(thio)pyrrolo[1,2-a]benzimidazol-1-one.

Alkyl- or Arylthiolation of Aryl Iodide via Cleavage of the S−S Bond of Disulfide Compound by Nickel Catalyst and Zinc

Various aryl sulfides can be synthesized by nickel-catalyzed alkyl- or arylthiolation of aryl iodide with a disulfide compound. This reaction produces Ni(0) from NiBr2-bpy by the reduction with zinc, and this generated complex works as an activating species to convert ArI into ArSR under neutral conditions. Furthermore, this system enables the use of two RS groups in (RS)2.

Flow injection system with in-line Winkler?s procedure using 16-way valve and spectrofluorimetric determination of dissolved oxygen in environmental waters

Flow injection spectrofluorimetry with in-line Winklers procedure was developed for the dissolved oxygen (DO) determination. 2-Thionaphthol reacted with iodine produced by Winkler’s method to form fluorescence inactive disulfide compound. To automate the process completely, a 5-channel flow system with a newly designed 16-way valve was assembled. The system consisted of a dispersion coil (DC), a precipitate formation coil (PFC), a precipitate dissolving coil (PDC), and extraction coil (EC). A calibration can be constructed by using a standard iodine solution for dissolved oxygen. The calibration graph was linear over the range 1.2×10−4∼6.0×10−4 mol l−1 iodine (1.96∼9.80 mg O l−1)). The relative standard deviation (n=6) was below 0.3% for the 4×10−4 mol l−1 iodine (6.27 mg O l−1) determination. The sample throughput was 12/h.

Flow injection system with in-line Winkler’s procedure using 16-way valve and spectrofluorimetric determination of dissolved oxygen in environmental waters

Flow injection spectrofluorimetry with in-line Winklers procedure was developed for the dissolved oxygen (DO) determination. 2-Thionaphthol reacted with iodine produced by Winkler’s method to form fluorescence inactive disulfide compound. To automate the process completely, a 5-channel flow system with a newly designed 16-way valve was assembled. The system consisted of a dispersion coil (DC), a precipitate formation coil (PFC), a precipitate dissolving coil (PDC), and extraction coil (EC). A calibration can be constructed by using a standard iodine solution for dissolved oxygen. The calibration graph was linear over the range 1.2×10−4∼6.0×10−4moll−1 iodine (1.96∼9.80mgOl−1)). The relative standard deviation (n=6) was below 0.3% for the 4×10−4moll−1 iodine (6.27mgOl−1) determination. The sample throughput was 12/h.

Decline in transcriptional activity of Nrf2 causes age-related loss of glutathione synthesis, which is reversible with lipoic acid.

Glutathione (GSH) significantly declines in the aging rat liver. Because GSH levels are partly a reflection of its synthetic capacity, we measured the levels and activity of gamma-glutamylcysteine ligase (GCL), the rate-controlling enzyme in GSH synthesis. With age, both the catalytic (GCLC) and modulatory (GCLM) subunits of GCL decreased by 47% and 52%, respectively (P < 0.005). Concomitant with lower subunit levels, GCL activity also declined by 53% (P < 0.05). Because nuclear factor erythroid2-related factor 2 (Nrf2) governs basal and inducible GCLC and GCLM expression by means of the antioxidant response element (ARE), we hypothesized that aging results in dysregulation of Nrf2-mediated GCL expression. We observed an approximately 50% age-related loss in total (P < 0.001) and nuclear (P < 0.0001) Nrf2 levels, which suggests attenuation in Nrf2-dependent gene transcription. By using gel-shift and supershift assays, a marked reduction in Nrf2/ARE binding in old vs. young rats was noted. To determine whether the constitutive loss of Nrf2 transcriptional activity also affects the inducible nature of Nrf2 nuclear translocation, old rats were treated with (R)-alpha-lipoic acid (LA; 40 mg/kg i.p. up to 48 h), a disulfide compound shown to induce Nrf2 activation in vitro and improve GSH levels in vivo. LA administration increased nuclear Nrf2 levels in old rats after 12 h. LA also induced Nrf2 binding to the ARE, and, consequently, higher GCLC levels and GCL activity were observed 24 h after LA injection. Thus, the age-related loss in GSH synthesis may be caused by dysregulation of ARE-mediated gene expression, but chemoprotective agents, like LA, can attenuate this loss.

Molecular structure and electrochemical properties of alkyldithiocarbamates

Cyclic voltammetry, chronoamperometry, chronocoulometry and rotating disc electrode techniques have been used to study redox properties of dithiocarbamate lithium salts solutes in 0.1 M LiClO 4/DMSO solution. The investigated compounds have been synthesized from N, N′-dimethylethylenediamine to which one or two dithiocarbonyl groups were attached by a reaction with CS 2 in an alkaline solution. Voltammetric studies of the oxidation of these moieties showed the irreversible, though reproducible, broad peak at scan rates ranging from 0.01 to 0.5 V s −1. The chronoamperometric and rotating disc electrode experiments confirmed the consumption of 1e/active group. Upon changing the electrode from Pt to glassy carbon only slight shift of the anodic peak potential, and negligible current change has been observed. These findings are interpreted as an indication that the electrode materials do not participate directly in the dithiocarbamate radicals formation (for example, via chemisorption) and in further dimerization of the radicals to thiuram disulfide. The latter process is assumed to proceed at the rate close to the diffusion limit. The calculated symmetry coefficient are distinctly lower than 0.5, the value predicted by the Butler–Volmer theory. Such an outcome implies that the potential range where the reaction proceeds is much more positive than the standard potential of the reaction. The oxidation of the compound containing two electroactive groups has led to the formation of a wide spectrum of diverse disulfide compounds differing one from another by the molecular weight (diffusion coefficient) owing to the various degree of the coupling. The semi-empirical quantum-chemical calculations showed the structure reorganization of the dithiocarbamate anions upon electron detachment enforced by localization of the unpaired electron on the sulfur atoms. It may favour kinetically the formation of thiuram disulfide through the fast homogeneous dimerization of the dithiocarbamate radicals.

A Novel and Efficient Method for the Technetium-99m Labelling of Disulfide Compounds Using a Tetrahydroborate Exchange Resin

Abstract A novel and efficient method for the technetium-99m labelling of disulfide compound 7 was established with high radiochemical purity in which tetrahydroborate exchange resin (BER) simultaneously carries out the reduction of 7, the reduction of [99mTc]pertechnetate and chelation of 7 with technetium-99m. The labelling occurs in a one-pot three-step procedure that is amenable to the preparation of 99mTc-radiopharmaceuticals.

Electronic properties of para-substituted thiophenols and disulfides from 13C NMR spectroscopy and ab initio calculations: relations to the Hammett parameters and atomic chargesElectronic supplementary information (ESI) available: all characterization data are tabulated in Table S1. A figure showing the dependence of the natural charge of the C1 atom of the disulfides on the 13C NMR chemical shift is also provided.

A large number of para-substituted benzene thiols and the corresponding disulfides were synthesized and characterized by 1H NMR, 13C NMR, and IR spectroscopies. Geometries of all sixteen thiols and fourteen disulfide compounds were optimized at the B3LYP/6-31G(d) level, while the electronic structure and the 13C isotropic shifts were calculated by ab initio Hartree-Fock method coupled with the Gauge-Independent Atomic Orbital (GIAO) algorithm and a 6-31+G(d,p) basis set. The calculated 13C NMR isotropic shifts exhibit admirable agreement (δ rmsd ∼4.6 ppm) with the experimental data. The chemical shift of para-substituted carbon showed a linear correlation with Hammett constants (σp and σp+). Using this methodology the σp+ constants for the dendritic ligands have been estimated to be 0.25 and 0.24 for 2(n) and 2(o), respectively. In addition, the NBO charges on the sulfur atoms shows a latent response with the σp+ parameter. The atomic charge on the thiophenolato sulfur is invariant with the electron withdrawing ability of the substituents, however, the charge increases with increasing electron-withdrawing power.