Spectroscopic investigation on the interaction of hyperbranched poly (amine) ester with model plasma protein: Effect on the structural and conformational changes

Mechanism of interaction between hyperbranched poly (amine) ester (HPAE) and bovine serum albumin (BSA) was investigated using fluorescence, synchronous fluorescence, three-dimensional fluorescence spectra, UV-Vis spectrometry and circular dichroism (CD). The structural and conformational changes of BSA induced by HPAE were also revealed in this study. Stern-Volmer analysis of fluorescence quenching showed that BSA fluorescence was statically quenched by HPAE, which implied that ground state complex formed between BSA and HPAE. Vander Waals force and hydrogen bond played major roles in the interaction of HPAE with BSA. The distance, r between the donor (BSA) and acceptor (HPAE) was calculated based on the Forster's theory of non-radiation energy transfer and was found to be 3.24 nm. Synchronous and three-dimensional fluorescence studies showed that the interaction of BSA with HPAE induced conformational changes in BSA. The secondary structural analysis by CD spectra suggested that HPAE binding induced BSA to form a more compact conformation with about 6.9% transformation of α-helix to β-sheet. Molecular model of the interaction of HPAE with BSA was also presented according to the results of this study.