摘要
在生理酸度(pH 7.4)条件下,利用荧光光谱法研究了甜蜜素与牛血清白蛋白(BSA)的相互作用。结果表明,甜蜜素与BSA形成基态复合物而引起BSA的内源性荧光猝灭,25℃时的结合常数为3.05×103 L·mol-1,结合位点数约等于1。利用Van’t Hoff方程计算出热力学参数:焓变(ΔHθ)和熵变(ΔSθ)分别为-3.46KJ·mol-1和48.23J·mol-1·K-1,表明疏水作用和氢键是维持BSA-甜蜜素复合物稳定的主要作用力。位点竞争实验表明,甜蜜素主要结合于BSA的亚域ⅡA,即site I位。同步荧光结果显示,甜蜜素与BSA的结合诱导BSA色氨酸残基所处微环境疏水性有所增加,而对酪氨酸残基微环境没有明显影响。Zn2+、Mg2+的存在对BSA-甜蜜素的结合有促进作用,而Ca2+、Fe3+、Cu2+则对BSA-甜蜜素复合物的形成有抑制作用。
In the current study,the interaction of sodium cyclamate with bovine serum albumin （BSA） under simulative physiological conditions （pH 7.4） was investigated by fluorescence spectroscopy technique. The observed result of fluorescence quenching indicated that a ground state complex was formed between sodium cyclamate and BSA,resulting in the intrinsic fluorescence quenching of BSA. The binding constant K at 25℃ was calculated to be 3.05 ;（ 103 L mol^-1 ,and the number of binding sites were approximately equal to 1. The calculated enthalpy change （△H^θ） and entropy change （△S^θ） values by Van＇t Hoff equation was - 3.46 KJ · mol^-1 and 48.23 J· mol^-1· K^-1 ,respectively. These findings suggested that hydrophobic interctions and hydrogen bonding were the main forces to maintain the stability of the BSA-sodium cyclamate complex. The site markers competitive experiments revealed the binding of sodium cyclamate to BSA primarily in the subdomain IIA （Site I） of BSA. Analysis of synchronous fluorescence spectra demonstrated that the hydrophobicity around tryptophan residues increased and the polarity weakened,but there was no obvious effect on the microenvironment of tyrosine residues of BSA. Moreover,the effects of some metal ions on the binding constant of BSA-sodium cyclamate interaction revealed that the presence of Zn^2＋ and Mg^2＋ could increase the stability of the BSA-sodium cyclamate complex,while the stability of the complex decreased in the presence of Ca^2＋ ,Fe^3＋ and Cu^2＋ ,respectively.
出处
《南昌大学学报（理科版）》
CAS
北大核心
2015年第2期158-162,共5页
Journal of Nanchang University(Natural Science)
基金
国家级大学生创新创业训练计划项目(20140403021)
南昌大学校级大学生创新创业训练计划项目(2014073)
江西省教育厅项目(GJJ14220)
国家自然科学基金资助项目(31060210)
关键词
甜蜜素
牛血清白蛋白
荧光猝灭
结合位点
sodium cyclamate
bovine serum albumin
fluorescence quenching
interaction
