Interaction of copper(II) complex of compartmental Schiff base ligand N,N′-bis(3-hydroxysalicylidene)ethylenediamine with bovine serum albumin

Circular dichroism (CD) spectroscopy, cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the interaction between copper(II) complex of compartmental Schiff base ligand (L), N,N'-bis(3-hydroxysalicylidene)ethylenediamine, and bovine serum albumin (BSA) in 0.1 mol dm(-3) phosphate buffer solution adjusted to physiological pH 7.0 containing 20% (w/w) dimethylsulfoxide at room temperature. CD spectra show that the interaction of the copper(II) complex with BSA leads to changes in the alpha-helical content of BSA and therefore changes in secondary structure of the protein with the slight red shift (2 nm) in CD spectra. From the voltammetric data, i.e. changes in limiting current with addition of BSA, the binding constant (K) of the interaction of copper(II) complex with BSA was found to be 1.96 x 10(4) dm(3) mol(-1). From the shifts in potential with the addition of BSA, the equilibrium constant ratio (K-2/K-1) for the binding of the oxidized (CuL)-L-II (K-1) and reduced (CuL)-L-1 (K-2) species to BSA was found to be 3.77, which shows that the reduced form (CuL)-L-I is bound more strongly to BSA than the oxidized form (CuL)-L-II. (c) 2006 Published by Elsevier B.V.