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Enzymes of glutathione metabolism and GSH content in copper-treated Scenedesmus bijugatus cells and the synthesis of metal-binding peptides are reported in this investigation. Progressive depletion of GSH content in the cells was observed with increasing concentrations of copper. There was an increase in the protein thiol content while the non-protein thiol content decreased. There was an initial elevation and later decrease in the hydrogen peroxide level in the cells. Copper stress increased the activities of gamma-glutamylcysteine synthetase, GSH S-transferase and GSH-peroxidase and decreased the activity of GSSG-reductase. These results suggest that copper alters the equilibrium between synthesis and utilization of GSH either due to its antioxidant role or by serving as a precursor in the synthesis of phytochelatins.

Nickel oxide (NiO) nano particle is synthesized by Ultrasound assisted one pot method and thus synthesized nano NiO is mixed with poly(vinyl alcohol) (PVA) to prepare the PVA/NiO nanocomposite. The influence of the composition on the structural modification on the composite is evaluated. The particle size and morphology of NiO nano material is confirmed by HRTEM. The structure and properties of the PVA/NiO nanocomposite material are characterized by FTIR, XRD, UV–Visible spectroscopy, DSC, TGA, and HRTEM. The synthesized PVA nanocomposite underwent hydrolytic oxidation reaction assisted by the effect of nano-sized NiO. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Metal sequestering potential of algae is being considered for the removal of heavy metals from contaminated aquatic ecosystems (Cai et al. 1995). Copper (Cu) is a bioelement and essential for metabolism (Kaim and Rall 1996). However, it is toxic at high concentrations and Cu salts are popular algicides. Hence, the mechanisms of toxicity and tolerance acquired by algae are of considerable significance (Prasad et al. 1998). Cu induces oxidative stress by generating reactive oxygen species like superoxide and hydroxyl radicals via Haber-Weiss and Fenton reactions. Oxidative stress directly damages proteins, amino acids, nucleic acids, porphyrins and phenolic substances etc. Free radicals also cause peroxidative degradation of polyunsaturated fatty acid chains of membrane lipids as evident by the increased formation of malondialdehyde (MDA), a product of lipid peroxidation (Shen et al. 1997a,b). The free radicals are also scavenged by non-enzymic substances like ascorbate, glutathione, α-tocopherol and glucose (De Vos and Schat 1991).