Liladhar B. Kumbhare

Correlating the GPx Activity of Selenocystine Derivatives with One-Electron Redox Reactions

With an aim to develop water soluble, less toxic glutathione peroxidase (GPx) mimics, three selenocystine (SeCys) derivatives, viz., selenocystamine (SeA), diselenodipropionic acid (SeP), and methyl ester of diselenodipropionic acid (MeSeP) have been synthesized and examined for GPx activity along with SeCys. The GPx activity of the compounds was found to be in the order SeCys ≅ SeA > MeSeP > SeP. The relative affinity of these GPx mimics towards the substrates thiol and hydroperoxide were determined by Lineweaver-Burk (L-B) plots. Since the enzyme activity involves several steps of reduction and oxidation reactions, attempts have been made to understand the role of such processes in deciding the efficacy of diselenides as GPx mimics. For this, one-electron redox chemistry of these compounds was studied in aqueous solutions at pH 7 using nanosecond pulse radiolysis technique. From these studies, it was concluded that SeCys and SeA, which can undergo easy one-electron reduction, exhibit high GPx activity.

Organochalcogenolates of Palladium(II) and Platinum(II): Versatile Molecular Precursors for Metal Chalcogenides

This presentation intends to discuss the design and synthesis of low temperature single source molecular precursors for the synthesis of palladium chalcogenides, both in bulk and nano-size regime. Thus a variety of organochalcogenolates of palladium and platinum differing in nuclearity (mono-, bi-, tri- and hexa- nuclear) have been isolated and characterized by uv-vis, NMR ( 1 H, 13 C, 31 P, 77 Se, 125 Te, 195 Pt) spectroscopy and X-ray crystallography. Thermal behavior of several complexes, such as [Pd(SeCOAr) 2 (PR 3 ) 2 ], [Pd(OAc)(ECH 2 CH 2 CH 2 NMe 2 )] 2 , etc. has been studied by TG analyses. Solvothermal decomposition yields palladium chalcogenides nano-particles (e.g., Pd 7 Te 3 , Pd 17 Se 15 ) which were characterized by XRD, EDAX and SEM method.

Group 12 metal monoselenocarboxylates: synthesis, characterization, structure and their transformation to metal selenide (MSe; M = Zn, Cd, Hg) nanoparticles

Reactions of [MCl2(tmeda)] with potassium salts of monoselenocarboxylic acids gave complexes of the general formula [M(SeCOR)2(tmeda)] (M = Zn, Cd; R = Ph, Tol; Tol = C6H4-p-CH3; tmeda = Me2NCH2CH2NMe2). The analogous mercury complexes were unstable at room temperature and afforded HgSe nanoparticles during the course of reaction. All the complexes were characterized by elemental analysis, IR, UV-vis, NMR (1H, 13C, 77Se, 113Cd) data. The X-ray structural analysis of [Cd(SeCOPh)2(tmeda)] revealed that the complex is a discrete monomer having an approximate tetrahedral coordination environment around the central metal atom with monodentate (Se-bonded) selenocarboxylates. Thermal behavior of these complexes was studied by TG analysis. Pyrolysis in a furnace or in HDA (hexadecylamine) gave MSe nanoparticles, which were characterized by XRD, EDAX, SEM and absorption spectroscopy.