表没食子儿茶素没食子酸酯和米糠蛋白的相互作用

Interaction Between Epigallocatechin Gallate and Rice Bran Protein

采用荧光光谱和紫外-可见光谱法研究表没食子儿茶素没食子酸酯(Epigallocatechin gallate,EGCG)和米糠蛋白(Rice bran protein,RBP)之间的相互作用。结果表明:EGCG对RBP有较强的荧光猝灭作用,为且动态和静态混合淬灭。EGCG与RBP在290、300、310 K时相互作用的表观结合常数分别为1.322 8×10~6、1.504 2×10~6、1.817 6×10~6 L/mol,对应的结合位点数分别为1.387 8、1.327 0、1.377 0。同步荧光光谱、紫外-可见光谱和三维荧光光谱表明EGCG主要影响RBP色氨酸残基空间结构的微环境,使其周围的疏水性下降。热力学参数表明EGCG与RBP结合的主要作用力为疏水相互作用。根据F?ster非辐射转移理论计算了不同条件下EGCG与RBP结合距离r为0.800 4 nm。建立了不同温度下EGCG与RBP结合率的理论模型,发现RBP的结合率随着EGCG浓度增大而减小,温度对两者的结合率无显著影响。

The interaction between epigallocatechin gallate(EGCG) and rice bran protein(RBP)was investigated by ?uorescence and ultraviolet-visible spectroscopy. The results indicated that EGCG had a strong ability to quench the fluorescence of RBP in the mixed of dynamic mode and static mode. The binding constants(K_A) and site numbers(n) obtained at different temperatures were 1.322 8×10~6L/moL, 1.387 8(290 K);1.504 2×10~6 L/moL, 1.3270(300 K);1.817 6×10~6 L/moL, 1.377 0(310 K), respectively. Synchronous fluorescence spectroscopy, ultraviolet-visible spectroscopy and three-dimensional fluorescence spectroscopy indicated that EGCG changed the microenvironment of tryptophan residues of RBP, which lead to decrease the hydrophobicity. According to the thermodynamic parameters, hydrophobic interaction played a dominant role in the interaction between EGCG and RBP. The binding distance between EGCG and RBP was calculated be to about 0.800 4 nm based on the theory of F?ster’s non-radiation energy transfer. The theoretical model of the binding ratio between EGCG and RBP at different temperatures was established. And the binding ratio between EGCG and RBP decreased as concentration of EGCG increased, while the temperature had no significant effect on the binding ratio.