Radiation-induced formation of polyacrylic acid–protein covalent conjugates

Abstract

Radiation-induced formation of water-soluble covalent conjugates of polyacrylic acid (PAA) with negatively charged proteins — bovine serum albumin (BSA) and superoxide dismutase (SOD) — was investigated at neutral pH. Aqueous solutions of PAA, BSA, SOD and their mixtures (PAA–BSA, PAA–Cu 2+–BSA, PAA–SOD) have been irradiated with 60Co γ-rays and the resulting changes have been measured by high-performance liquid chromatography and UV–Visible spectrophotometry. Crosslinking and formation of water-soluble conjugates of PAA with BSA molecules upon irradiation were observed in the PAA–BSA and PAA–Cu 2+–BSA mixtures. In contrast to these systems, Cu(II), Zn(II) ions in the structure of SOD molecules protect the free protein, and the protein component of PAA–SOD mixtures against radiation damage, and prevent the PAA–SOD covalent conjugate formation. The mechanism of observed protection effect is discussed.