Zhang Liangliang, Sahu Indra Dev, Xu Man, Wang Yongmei, Hu Xinyu
Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China.
Chemistry and Biochemistry Department, Miami University, Oxford, OH 45056, USA.
Food Chem. 2017 Apr 15;221:1923-1929. doi: 10.1016/j.foodchem.2016.11.158. Epub 2016 Dec 1.
The effects of metal ions (Cu, Sn, Zn, Mn, Al and Fe) on the interaction between (-)-epigallocatechin-3-gallate (EGCg) and β-lactoglobulin (β-Lg) were investigated via fluorescence and circular dichroism (CD) spectroscopy. The results of the fluorescence titration experiment demonstrated that the addition of Cu increases the quenching efficiency of EGCg to β-Lg by more than EGCg alone, while Mn, Al and Zn decrease the quenching efficiency of EGCg to β-Lg by less than EGCg alone. [β-Lg-Mn], [β-Lg-Al], [β-Lg-Zn] and [β-Lg-Sn] obviously decreased the apparent binding affinities (K) of EGCg to β-Lg by 95.53%, 81.94%, 44.66% and 38.58%, respectively, whereas [β-Lg-Cu] significantly increased the K of EGCg for β-Lg by 115.44%. The results of CD spectroscopy experiment showed the α-helix content of β-Lg decreased with the addition of Cu or Al, indicating that the β-Lg-Cu and β-Lg-Al interaction resulted in unfolding of the secondary structure of β-Lg.
通过荧光光谱和圆二色光谱（CD）研究了金属离子（铜、锡、锌、锰、铝和铁）对（-）-表没食子儿茶素-3-没食子酸酯（EGCg）与β-乳球蛋白（β-Lg）之间相互作用的影响。荧光滴定实验结果表明，添加铜使EGCg对β-Lg的猝灭效率比单独的EGCg更高，而锰、铝和锌使EGCg对β-Lg的猝灭效率比单独的EGCg更低。[β-Lg-锰]、[β-Lg-铝]、[β-Lg-锌]和[β-Lg-锡]分别使EGCg与β-Lg的表观结合亲和力（K）明显降低了95.53%、81.94%、44.66%和38.58%，而[β-Lg-铜]使EGCg对β-Lg的K显著增加了115.44%。CD光谱实验结果表明，添加铜或铝后β-Lg的α-螺旋含量降低，这表明β-Lg-铜和β-Lg-铝之间的相互作用导致β-Lg二级结构展开。
