Effect of copper ions on the radiostability of protein-polyelectrolyte mixtures

Aqueous solution of polyacrylic acid (PAA), poly-N-isopropylacrylamide (PNIPAAm), bovine serum albumin (BSA), superoxide dismutase (SOD) and their mixtures (PAA-BSA, PAA-Cu-BSA, PNIPAAm-BSA, PAA-SOD) were irradiated in the presence of oxygen in neutral media (pH 7.0) with Co-60 gamma-rays. In addition, aliquots of aqueous solutions of PAA, PAA-Cu2+, BSA and PAA-Cu2+-BSA saturated with N-2 and N2O were also irradiated. The decomposition rate of irradiated solutions were measured by UV-visible spectrophotometry, fluorescence spectroscopy, and high performance liquid chromatography (HPLC). Protective effect of copper ions on radiolysis of aqueous solution of PAA-Cu-BSA and conversion of Cu(II) to Cu(I) was observed. The possible mechanism of this phenomenon is discussed.