X-band electron paramagnetic resonance spectra of pig serum albumin-copper(II) and pig serum albumin-copper(II)-amino acid systems

Abstract

EPR spectra of the binary, PSA-copper(II) (1:1 and 2:1) and ternary systems, PSA-copper(II) -amino acid (1:1:1) have been studied. In binary system, two distinct EPR features have been observed, one of the features (towards the low field), showing broad and overlapping signals is attributed to non-specific bonding of copper(II) to albumin and other feature (towards higher field), showing sharp intense signals is attributed to specific bonding. The change from non-specific to specific bonding is favoured by increase in <i>p</i>H as well as by increase in protein concentration. Observed <i>p</i>H for transition from non-specific binding is 10.00 <<i>p</i>H < 11.30. A better resolution of nitrogen hyperfine couplings are obtained for both binary, PSA-Cu(II) (1:1 and 2:1) and ternary PSA-Cu(II)-amino ac id (1:1:1) systems. Seven and more than seven nitrogen superhyperfine lines are observed in g region of binary and ternary systems respectively.