Quenching and binding mechanism of the intrinsic fluorescence of bovine serum albumin by 5-phenyl-10,15,20-tri-(4-pyridyl)-porphyrin

Abstract

The binding interaction mechanism between 5-phenyl-10,15,20-tri-(4-pyridyl)-porphyrin (TriPyP) and bovine serum albumin (BSA) was investigated by the fluorescence method and presented in this paper. Based on the mechanism of fluorescence quenching of BSA caused by TriPyP, the binding constants between TriPyP and BSA were measured at different temperatures by fluorescence spectroscopy at pH 7.40. As the binding constants decreased with increasing temperature, the type of quenching between TriPyP and BSA was determined as static quenching. Based on the Förster theory of non-radiation energy transfer, the binding distance and energy transfer efficiency at 25 °C between TriPyP (acceptor of energy) and BSA (donor of energy) were obtained. The results confirmed that the interaction was similar to non-radiation energy transfer. According to the thermodynamic parameters, the main type of binding force between TriPyP and BSA could be deduced as electrostatic force. Using synchronous fluorescence spectra, the effect of TriPyP on conformation of BSA was studied, and the hydrophobicity in microenvironment was developed by TriPyP. All these experimental results and theoretical data clarified that TriPyP could bind to BSA and be effectively transported in the human body, which could be a useful guideline for further drug design.