Synthetic glutathione peroxidase mimics: effect of nucleophilicity of the aryl thiol cofactor on the antioxidant activity

Catalytic activity of a series of potent amide- and amine-based organoselenium compounds are studied in the presence of various aromatic thiols having electron donating and electron withdrawing substituents on the phenyl ring. This study suggests that the antioxidant activities of the synthetic GPx mimics can be significantly increased by the incorporation of a suitable electron donating group on the phenyl ring of an aromatic thiol.

A Thiol- ene Clickable Hyperbranched Polyester via a Simple Single- Step Melt Trans- Esterification Process

Self-condensation of AB(2) type monomers (containing one A-type and two B-type functional groups) generates hyperbranched (HB) polymers that carry numerous B-type end-groups at their molecular periphery; thus, development of synthetic methods that directly provide quantitatively transformable peripheral B groups would be of immense value as this would provide easy access to multiply functionalized HB systems. A readily accessible AB(2) monomer, namely diallyl, 5-(4-hydroxybutoxy)isophthalate was synthesized, which on polymerization under standard melt-transesterfication conditions yielded a peripherally clickable HB polyester in a single step; the allyl groups were quantitatively reacted with a variety of thiols using the facile photoinitiated thiol-ene reaction to generate a wide range of derivatives, with varying solubility and thermal properties. Furthermore, it is shown that the peripheral allyl double bonds can also be readily epoxidized using meta-chloroperoxybenzoic acid to yield interesting HB systems, which could potentially serve as a multifunctional cross-linking agent in epoxy formulations. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40248.

Maximin 9, a novel free thiol containing antimicrobial peptide with antimycoplasma activity from frog Bombina maxima

Amphibian skin is a rich resource of antimicrobial peptides, like maximins and maximin Hs from frog Bombina maxima. Novel cDNA clones encoding a precursor protein, which comprises a novel maximin peptide (maximin 9) and reported maximin H3, were isolated from two constructed skin cDNA libraries of B. maxima. The predicted primary structure of maximin 9 is GIGRKFLGGVKTTFRCGVKDFASKHLY-NH2. A surprising substitution is at position 16, with a free cysteine in maximin 9 rather than usual conserved glycine in other reported maximins. Maximin 9, the homodimer form and its Cys(16) to Gly(16) mutant were synthesized and their antimicrobial activities were evaluated. Unlike previously reported maximin 3, the tested bacterial and fungal strains were resistant to maximin 9, its homodimer and the Cys(16) to Gly(16) mutant (with MICs > 100 mu M). On the other hand, interestingly, while eight clinical Mollicutes strains were generally resistant to maximin 9 homodimer and its Cys(16) to Gly(16) mutant, most of them are sensitive to maximin 9 at a peptide concentration of 30 mu M, especially in the presence of dithiothreitol. These results indicate that the presence of a reactive Cys residue in maximin 9 is important for its antimycoplasma activity. The diversity of antimicrobial peptide cDNA structures encountered in B. maxima skin cDNA libraries and the antimicrobial specificity differences of the peptides may reflect well the species' adaptation to the unique microbial environments. (c) 2005 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

A study of low-energy ion induced radiolysis of thiol-containing amino acid cysteine in the solid and aqueous solution states

The radiolysis of cysteine under plasma discharge and irradiation of low-energy Ion beam was investigated. The damage of cysteine in aqueous solution under discharge was assessed via the acid ninhydrin reagent and the yield of cystine produced from the reaction was analyzed by FTIR In addition, the generation of hydrogen sulfide was also identified The destruction of solid cysteine under low-energy ion beam irradiation was estimated via monitoring IR bands of different functional groups (-SH, -NH3, -COO-) of cysteine. and the production of cystine from ion-irradiated solid cysteine after dissolution in water was also verified These results may help us to understand the inactivation of sulphydryl enzymes under direct and indirect interaction with the low-energy ion irradiation (C) 2010 Elsevier B V All rights reserved.

Thia-michael addition reactions in water using 3-[Bis(alkylthio) methylene]pentane-2,4-diones as odorless and efficient thiol equivalents

3-[Bis(ethylthio)methylene]pentane-2,4-dione (1a) and 3-[bis(benzylthio)methylene]pentane-2,4-dione (1b) have been investigated as non-thiolic and odorless thiol equivalents in thia-Michael addition reactions. In the presence of aqueous p-dodecyl benzenesulfonic acid (DBSA), compound (1) was cleaved and the generated thiols underwent facile conjugate addition to alpha,beta-unsaturated ketones 2 in-situ, affording the corresponding beta-keto sulfides (3) in good yields.

Surface charge influence on the surface plasmon absorbance of electroactive thiol-protected gold nanoparticles

Gold nanoparticles (3.1-5.0 nm in size) surface-derivatized with both electroactive and nonelectroactive self-assembled monolayers were synthesized. The surface-derivatized electroactive particles can be easily oxidized/reduced at an electrode surface based on the diffusion-controlled current-voltage curve observed in cyclic voltammetry measurements. Spectroelectrochemical investigation demonstrated that the maximum absorbance of the nanoparticles in their oxidized state red-shifted compared with their reduced state to a different extent according to their size distribution. In the case of the particles surface-derivatized with nonelectroactive monolayers, much less shift was observed. This study showed that surface plasmon absorbance of gold nanoparticles was not only related to core charge states but was also influenced by surface charge states as well.

A novel method to construct a third-generation biosensor: self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres

A novel method for fabrication of horseradish peroxidase (HRP) biosensor has been developed by self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization of St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups. Finally, horseradish peroxi- dase was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The sensor was highly sensitive to hydrogen peroxide with a detection limit of 4.0 mumol l(-1), and the linear range was from 10.0 mumol l(-1) to 7.0 mmol l(-1). The biosensor retained more than 97.8% of its original activity after 60 days of use. Moreover, the Studied biosensor exhibited good current repeatability and good fabrication reproducibility.

Self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres for fabrication of a mediatorless biosensor

A novel strategy to construct a sensitive mediatorless sensor of H2O2 was described. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups and formed monolayers on the surface of poly(St-co-AA) nanospheres. Finally, horseradish peroxidase (HRP) was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The biosensor showed a linear range of 8.0 mu mol L-1-7.0 mmol L-1 with a detection limit of 4.0 mu mol L-1. The biosensor retained more than 97.8% of its original activity after 60 days' storage. Moreover, the studied biosensor exhibited good current reproducibility and good fabrication reproducibility.