摘要
采用荧光猝灭和同步荧光法,研究了磷酸缓冲溶液(PBS,pH=7.4)中有无碳纳米管(CNTs)共存时,荧光活性物质槲皮素(Qct)与牛血清白蛋白(BSA)和酪蛋白(Cas)的相互作用.推导了方法1(固定蛋白质浓度,改变Qct浓度,测量蛋白质荧光改变)和方法2(固定Qct浓度,改变蛋白质浓度,测量Qct荧光改变)研究分子间作用的一般方程,由非线性最小二乘拟合法测算了结合常数K和摩尔结合比n,并藉此定量评估了"光内滤所致猝灭"效应的影响.研究了共存CNTs或Qct对BSA或Cas的荧光猝灭效应,及CNTs对Qct-BSA和Qct-Cas相互作用的影响.以同步荧光法考察了CNTs或Qct对BSA或Cas构象的影响,并测算了CNTs或Qct与蛋白质中酪氨酸(Tyr)或色氨酸(Trp)残基相关的K和n.结果表明,CNTs主要与处于蛋白质分子表面附近的Trp残基作用,而小分子Qct则还可与处于蛋白质分子内部的Tyr残基作用.
Fluorescence quenching and synchronous fluorescence methods were used to study the interactions of fluorescence-active quercetin （Qct） with casein （Cas） and bovine serum albumin （BSA） in phosphate buffer solution （PBS, pH=7.4） with or without coexisting carbon nanotubes （CNTs）. Formulae for binding constant （K） and molar binding ratio （n） were established for methods i （fixing protein concentration, changing Qct concentration, and monitoring the fluorescence of protein） and 2 （fixing Qct concentration, changing protein concentration, and monitoring the fluorescence of Qct）, to which values of K and n were calculated via nonlinear least-square fitting of the experimental data, and the ＂optical inner filtering induced fluorescence quenching＂ effect was thus quantitatively evaluated. The quenching effects of coexisting CNTs on the fluorescence of Qct, BSA, and Cas, as well as the effects of coexisting CNTs on Qct-BSA and Qct-Cas interactions, were examined. Synchronous fluorescence was also used to examine the effects of coexisting CNTs and Qct on conformations of BSA and Cas, with relevant K and n values for tyrosine （Tyr） and tryptophan （Trp） residues estimated. It was concluded that the CNTs mainly interact with the Trp residues locating near the protein surfaces, but small-sized Qct molecules could further interact with the Tyr residues locating inside the protein molecules.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2008年第3期379-387,共9页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(20675029,90713018,20335020)
湖南省教育厅(04C383,05A036)资助项目
关键词
碳纳米管
槲皮素
酪蛋白
牛血清白蛋白
荧光猝灭
同步荧光
分子间作用
Carbon nanotubes
Quercetin
Casein
Bovine serum albumin
Fluorescence quenching
Synchronous fluorescence
Intermolecular interactions
