College of Chemistry and Environmental Engineering, Yangtze University, Jingzhou, 434023, Hubei, People's Republic of China.
Mol Biol Rep. 2012 May;39(5):5115-23. doi: 10.1007/s11033-011-1307-z. Epub 2011 Dec 9.
In this work, fluorescence spectroscopy in combination with circular dichroism spectroscopy and molecular modeling was employed to investigate the binding of 10-hydroxycamptothecin (HCPT) to human serum albumin (HSA) under simulative physiological conditions. The experiment results showed that the fluorescence quenching of HSA by HCPT was a result of the formation of HCPT-HSA complex. The corresponding association constants (K (a)) between HCPT and HSA at four different temperatures were determined according to the modified Stern-Volmer equation. The results of thermodynamic parameters ΔG, ΔH, and ΔS indicated that hydrogen bonds and van der Waals forces played major roles for HCPT-HSA association. Site marker competitive displacement experiment indicated that the binding of HCPT to HSA primarily took place in sub-domain IIA (site I). Molecular docking study further confirmed the binding mode and the binding site obtained by fluorescence and site marker competitive experiments. The conformational investigation showed that the presence of HCPT decreased the α-helical content of HSA and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of HSA molecules.
在这项工作中，荧光光谱学结合圆二色光谱学和分子建模被用于在模拟生理条件下研究 10-羟基喜树碱（HCPT）与人血清白蛋白（HSA）的结合。实验结果表明，HCPT 对 HSA 的荧光猝灭是 HCPT-HSA 复合物形成的结果。根据改进的 Stern-Volmer 方程，确定了在四个不同温度下 HCPT 与 HSA 之间相应的结合常数（K(a)）。热力学参数 ΔG、ΔH 和 ΔS 的结果表明，氢键和范德华力对 HCPT-HSA 结合起主要作用。位点标记竞争置换实验表明，HCPT 与 HSA 的结合主要发生在亚域 IIA（位点 I）。分子对接研究进一步证实了荧光和位点标记竞争实验获得的结合模式和结合位点。构象研究表明，HCPT 的存在降低了 HSA 的α-螺旋含量，并诱导蛋白质多肽的轻微展开，这证实了 HSA 分子的一些微环境和构象变化。
