Zhang Ye-Zhong, Xiang Xia, Mei Ping, Dai Jie, Zhang Lin-Lin, Liu Yi
Department of Chemistry, Yangtze University, Jingzhou, Hubei, PR China.
Spectrochim Acta A Mol Biomol Spectrosc. 2009 May;72(4):907-14. doi: 10.1016/j.saa.2008.12.007. Epub 2008 Dec 24.
The binding interaction of Congo Red (CGR) with bovine serum albumin (BSA) was investigated by spectroscopic techniques including fluorescence spectroscopy, UV-vis absorption, and circular dichroism (CD) spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by CGR was the result of the formation of a BSA-CGR complex, and the corresponding binding constants (K(a)) at the four different temperatures (292, 298, 304, and 310K) were obtained according to the modified Stern-Volmer equation. The thermodynamic parameters DeltaH and DeltaS were calculated to be -12.67kJmol(-1) and 58.60Jmol(-1)K(-1), respectively, which suggested that both hydrophobic force and hydrogen bond played major roles in stabilizing the BSA-CGR complex. Site marker competitive experiments showed that the binding of CGR to BSA primarily took place in site I of BSA. The distance r between CGR (acceptor) and tryptophan residues of BSA (donor) was calculated to be 3.89nm based on Förster's non-radioactive energy transfer theory. The conformational investigation showed that the presence of CGR resulted in the change of BSA secondary structure and induced the slight unfolding of the polypeptides of protein, which confirmed some micro-environmental and conformational changes of BSA molecules.
在模拟生理条件下,采用荧光光谱、紫外可见吸收光谱和圆二色光谱等光谱技术研究了刚果红(CGR)与牛血清白蛋白(BSA)的结合相互作用。荧光数据表明,CGR对BSA的荧光猝灭是形成BSA-CGR复合物的结果,并根据修正的Stern-Volmer方程获得了四个不同温度(292、298、304和310K)下相应的结合常数(K(a))。计算得到的热力学参数ΔH和ΔS分别为-12.67kJmol(-1)和58.60Jmol(-1)K(-1),这表明疏水作用力和氢键在稳定BSA-CGR复合物中均起主要作用。位点标记竞争实验表明,CGR与BSA的结合主要发生在BSA的位点I。基于Förster非辐射能量转移理论,计算出CGR(受体)与BSA的色氨酸残基(供体)之间的距离r为3.89nm。构象研究表明,CGR的存在导致了BSA二级结构的变化,并诱导了蛋白质多肽的轻微展开,这证实了BSA分子的一些微环境和构象变化。