Study on the Interaction between Theasinesin and Bovine Serum Albumin by Fluorescence Method

Author： Zhang Wenming Han Benyong Zhao Shenglan Ge Feng Xiong Xiangfeng Chen Dan Liu Diqiu Chen Chaoyin

ISSN： 0003-2719

Source： Analytical Letters, Vol.43, Iss.2, 2010-01, pp. : 289-299

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Abstract

Theasinesin (TS), a polymer of epigallocatechin gallate, is the main active component of tea polyphenols. Several studies indicate that tea polyphenols have extensive pharmacology activity. However, there is little research about the transportation and metabolism of tea polyphenols in vivo. Serum albumin is a most important protein serving as a depot protein and as a transport protein for many drugs and other bioactive small molecules. This study observed the interaction between TS and bovine serum albumin (BSA) by fluorescence and absorption spectroscopy. The results showed that both static and dynamic quenching occurred in the fluorescence quenching of BSA by TS. The binding sites number is 1.1845 and the binding sites may close to the tyrosine residues. The thermodynamic parameters ∆H°, ∆G°, ∆S° at temperatures 310 K were calculated 1.7 KJ, -35.4 KJ, and 0.12 KJ. The negative sign of free energy (∆G°) means that the interaction process is spontaneous. The positive enthalpy (∆H°) and entropy (∆S°) values of the interaction of TS and BSA indicate that the binding is mainly entropy-driven and the enthalpy is unfavorable for it, the hydrophobic forces playing a major role in the reaction. A distance of 4.037 nm was found between donor (BSA) and acceptor (TS), obtained according to the Főrster theory of non-radiation energy transfer, which indicates that the energy transfer from BSA to TS occurs with high probability. The results of synchronous fluorescence spectra and UV-vis absorption spectra showed that the peptide strands of BSA molecules extended more and the hydrophobicity decreased with the addition of TS.