不同pH值环境下β-乳球蛋白与咖啡中3种主要多酚之间的相互作用

Interactions betweenβ-Lactoglobulin and Three Major Polyphenols in Coffee under Different pH Environments

利用多光谱学和分子对接技术,探究在不同pH值条件下,咖啡中的3种主要多酚(绿原酸、咖啡酸和阿魏酸)与牛乳中β-乳球蛋白间的非共价相互作用及对蛋白结构的影响。结果表明,在两种pH值环境下,3种咖啡多酚均通过静态猝灭有效地猝灭β-乳球蛋白的荧光,在pH 7.4、温度298 K时,绿原酸、咖啡酸和阿魏酸对β-乳球蛋白的猝灭常数(K_(sv))分别为6.53×10^(4)、3.16×10^(4)L/mol及3.09×10^(4)L/mol,结合位点数分别为1.20、1.02和1.14,能量转移效率分别为34.55%、24.56%和21.35%;pH 3.0、温度298 K时,K_(sv)分别为7.18×10^(4)、5.24×10^(4)L/mol及7.12×10^(4)L/mol,结合位点数为1.28、1.18和1.25,能量转移效率分别提高至34.70%、30.42%和29.65%。在pH 7.4时,β-乳球蛋白α-螺旋含量降低,β-折叠含量增加;pH 3.0时,β-折叠含量增加,无规卷曲含量降低。分子对接结果表明,3种多酚主要通过氢键和范德华力以及疏水相互作用结合在β-乳球蛋白的疏水口袋。本研究初步揭示不同pH值条件下咖啡乳饮料中β-乳球蛋白和绿原酸、咖啡酸及阿魏酸间的相互作用机制。

The purpose of this study was to explore the non-covalent interactions between three major polyphenols(chlorogenic acid,caffeic acid and ferulic acid)in coffee andβ-lactoglobulin(β-LG)at different pH values and their effects on protein structure by multispectroscopic techniques and molecular docking.The results showed that all three coffee polyphenols statically quenched the fluorescence ofβ-lactoglobulin under two pH conditions.At pH 7.4 and 298 K,the quenching constants(K_(sv))of chlorogenic acid,caffeic acid and ferulic acid forβ-lactoglobulin were 6.53×10^(4),3.16×10^(4)and 3.09×10^(4)L/mol with 1.20,1.02 and 1.14 binding sites and energy transfer efficiency of 34.55%,24.56%and 21.35%,respectively.At pH 3.0 and 298 K,the K_(sv)were 7.18×10^(4),5.24×10^(4)and 7.12×10^(4)L/mol with 1.28,1.18 and 1.25 binding sites and energy transfer efficiency of 34.70%,30.42%and 29.65%,respectively.The results of circular dichroism showed that theα-helix content ofβ-LG decreased and theβ-sheet content increased at pH 7.4,and theβ-sheet content increased and the random coil content decreased at pH 3.0.The results of molecular docking showed that the three polyphenols could bind to the hydrophobic pocket ofβ-lactoglobulin mainly through hydrogen bonds,van der Waals force and hydrophobic interaction.This study preliminarily revealed the interaction mechanism betweenβ-lactoglobulin and chlorogenic acid,caffeic acid and ferulic acid in coffee milk beverage under different pH conditions.