牛血清白蛋白与十二烷基硫酸钠作用的机理

Mechanism of Interaction between Bovine Serum Albumin and Sodium Dodecyl Sulfate

利用电动势法得到了牛血清白蛋白(BSA)与十二烷基硫酸钠(SDS)相互作用的结合等温线.通过四阶导数紫外光谱法和荧光光谱法研究了相互作用过程中芳香族氨基酸残基微环境极性的变化.通过研究发现,随着SDS浓度的逐渐增大,SDS在BSA上的平均结合数(ν)逐渐增大,色氨酸(Trp)残基所处微环境的极性在减弱后保持基本不变,酪氨酸残基所处微环境的极性在明显增强后稍有减弱,苯丙氨酸残基所处微环境的极性略有增强.结果表明,当ν由0增大到14时,SDS主要结合在BSA的Trp-213附近并逐渐形成聚集体,从而诱导BSA由结构域IIA开始逐渐展开.此后,SDS呈正协同作用的特点与BSA结合,ν急剧增大.当ν约为302时,SDS在BSA上的结合基本达到饱和,BSA的构象趋于稳定.

The binding isotherms of the interaction between bovine serum albumin （BSA） and sodium dodecyl sulfate （SDS） were obtained using electromotive force measurements. Changes in the microenvironmental polarity of aromatic amino acid residues during the interaction were studied using fourth-derivative ultraviolet spectroscopy and fluorescence spectroscopy. The average number （v） of SDS molecules bound to BSA increased with increasing SDS concentration. The polarity of tryptophan （Trp） residues decreased gradually and then remained almost constant. The polarity of tyrosine residues increased significantly and then decreased a little. The polarity of phenylalanine residues increased very slightly. The results show that SDS molecules bind to BSA in the vicinity of Trp-213 when v gradually increases from 0 to 14. BSA unfolds from domain IIA, induced by SDS aggregates formed near Trp-213. The v value then increases rapidly as a result of positive cooperative binding. When the v value reaches about 302, saturation binding is achieved and the BSA conformation remains almost unchanged.