Spectroscopic Investigation on the Interaction of Ferrocene Containing Hyperbranched Poly(amine) Ester with Model Plasma Protein

Abstract

Mechanism of interaction between ferrocenyl-functionalized hyperbranched poly(amine) ester (HPAE-Fc) and model plasma protein-bovine serum albumin (BSA) was investigated using cyclicvoltammetry, differential pulsed voltammetry, fluorescence, UV–Vis absorption spectrometry and circular dichroism (CD). Some complicated interactions occurred between BSA and HPAE-Fc and the new redox centers appeared in the BSA/HPAE-Fc complex that changed and hindered the electron transfer of Fe/Fe2+. Stern–Volmer analysis of fluorescence quenching data showed that BSA fluorescence was statically quenched by HPAE-Fc, which implied that ground state complex formed between BSA and HPAE-Fc. The hydrogen bonds and vander Waals force play major roles in the reaction as indicated by the 1H NMR and variable temperature 1H NMR spectra and thermodynamic parameters. The distance, r between the donor (BSA) and acceptor (HPAE-Fc) was calculated based on the Forster’s theory of non-radiation energy transfer and was found to be 3.24 nm, which in turn indicated that HPAE-Fc can bind to BSA with high probability. Synchronous, three-dimensional fluorescence and CD studies indicated that the interaction of BSA with HPAE-Fc induced conformational changes in BSA with overall decrease in the α-helical structure and increase in β-pleated sheet structure. The molecular model of the interaction between HPAE-Fc and BSA was also presented according to the results in this study.