Author(s)

Xiaoyan Gao, Yingcai Tang, Wanqi Rong, Xiaoping Zhang, Wujie Zhao, Yanqin Zi

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The interaction between captopril, an inhibitor of angiotensin converting enzyme and human serum albumin, a principal plasma protein in the liver has been investigated in vitro under a simulated physiological condition by UV-vis spectrophotometry and fluorescence spectrometry. The intrinsic fluorescence intensity of human serum albumin was strongly quenched by captopril. The binding constants and the number of binding sites can be calculated from the data obtained from fluorescence quenching experiments. The negative value of ΔG⁰ reveals that the binding process is a spontaneous process. According to the van’t Hoff equation, the standard enthalpy change (ΔH⁰) and standard entropy change (ΔS⁰) for the reaction were calculated to be 35.98 KJ●mol^-1 and 221.25 J●mol^-1 K. It indicated that the hydrophobic interactions play a main role in the binding of captopril to human serum albumin. In addition, the distance between captopril (acceptor) and tryptophan residues of human serum albumin (donor) was estimated to be 1.05 nm according to the Förster’s resonance energy transfer theory. The results obtained herein will be of biological significance in pharmacology and clinical medicine.

Human Serum Albumin, Captopril, Fluorescence Quenching, Stern-Volmer Equation, The Förster’s Resonance Energy Transfer Theory

X. Gao, Y. Tang, W. Rong, X. Zhang, W. Zhao and Y. Zi, "Analysis of Binding Interaction between Captopril and Human Serum Albumin," American Journal of Analytical Chemistry, Vol. 2 No. 2, 2011, pp. 250-257. doi: 10.4236/ajac.2011.22030.