Multispectroscopic studies on the interaction of a platinum(II) complex containing L-histidine and 1,10-phenanthroline ligands with bovine serum albumin.

The mechanism of the interaction between bovine serum albumin (BSA) and Pt(phen) (histidine) complex was studied employing ultraviolet (UV) absorption, circular dichroism (CD), FT-IR, differential pulse voltammetry (DPV), and fluorescence spectral methods. Fluorescence data showed that the intrinsic fluorescence of BSA was strongly quenched by Pt(II) complex in terms of an untypical static quenching process. The corresponding number of binding sites (n) and binding constant (K b) of BSA and complex at 283, 298, and 310 K were calculated to be 0.61 × 10(6), 19 × 10(6), and 42 × 10(6) M(-1), respectively. The results showed that the increasing temperature improves the stability of the complex-BSA system, which results in a higher binding constant and the number of binding sites of the complex-BSA system. The positive ΔH and positive ΔS indicated that hydrophobic forces might play a major role in the binding between complex and BSA. Based on Forster's theory of non-radiation energy transfer, the binding distance (r) between the donor (BSA) and acceptor (Pt(II) complex) was evaluated. The results of CD, UV-vis, DPV, and FT-IR spectroscopy showed that the binding of Pt(II) complex to BSA induced conformational changes in BSA.