Cheng Xiao-Xia, Lui Yi, Zhou Bo, Xiao Xiao-He, Liu Yi
State Key Laboratory of Virology, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 Jun;72(5):922-8. doi: 10.1016/j.saa.2008.12.003. Epub 2008 Dec 13.
Berbamine, a naturally occurring isoquinoline alkaloid extracted from Berberis sp., is the active constituent of some Chinese herbal medicines and exhibits a variety of pharmacological activities. The effects of berbamine on the structure of bovine serum albumin (BSA) were investigated by circular dichroism, fluorescence and absorption spectroscopy under physiological conditions. Berbamine caused a static quenching of the intrinsic fluorescence of BSA, and the quenching data were analyzed by application of the Stern-Volmer equation. There was a single primary berbamine-binding site on BSA with a binding constant of 2.577x10(4)Lmol(-1) at 298K. The thermodynamic parameters, enthalpy change (DeltaH(0)) and entropy change (DeltaS(0)) for the reaction were -76.5kJmol(-1) and -173.4Jmol(-1)K(-1) according to the van't Hoff equation. The results showed that the hydrogen bond and van der Waals interaction were the predominant forces in the binding process. Competitive experiments revealed a displacement of warfarin by berbamine, indicating that the binding site was located at Drug sites I. The distance r between the donor (BSA) and the acceptor (berbamine) was obtained according to the Förster non-radiation energy transfer theory. The results of three-dimensional fluorescence spectra, UV-vis absorption difference spectra and circular dichroism of BSA in the presence of berbamine showed that the conformation of BSA was changed. The results provide a quantitative understanding of the effect of berbamine on the structure of bovine serum albumin, providing a useful guideline for further drug design.
小檗胺是从十大功劳属植物中提取的一种天然异喹啉生物碱，是一些中草药的活性成分，具有多种药理活性。在生理条件下，通过圆二色性、荧光和吸收光谱研究了小檗胺对牛血清白蛋白（BSA）结构的影响。小檗胺导致BSA的固有荧光发生静态猝灭，并应用Stern-Volmer方程对猝灭数据进行分析。在298K时，BSA上有一个单一的主要小檗胺结合位点，结合常数为2.577×10⁴L·mol⁻¹。根据范特霍夫方程，该反应的热力学参数，即焓变（ΔH⁰）和熵变（ΔS⁰）分别为-76.5kJ·mol⁻¹和-173.4J·mol⁻¹·K⁻¹。结果表明，氢键和范德华相互作用是结合过程中的主要作用力。竞争实验表明，小檗胺可取代华法林，表明结合位点位于药物位点I。根据Förster非辐射能量转移理论，获得了供体（BSA）和受体（小檗胺）之间的距离r。小檗胺存在下BSA的三维荧光光谱、紫外可见吸收差光谱和圆二色性结果表明，BSA的构象发生了变化。这些结果为定量了解小檗胺对牛血清白蛋白结构的影响提供了依据，为进一步的药物设计提供了有用的指导。
