Institut de recherche sur les nutraceutiques et les aliments fonctionnels (INAF/STELA), Université Laval, Québec, QC, Canada.
J Phys Chem B. 2010 May 20;114(19):6707-12. doi: 10.1021/jp101096r.
Beta-lactoglobulin (beta-LG), the major whey protein in bovine milk, binds to a wide range of compounds. Folic acid (FA) is a synthetic form of the B group vitamin known as folates, which are essential cofactors for a variety of physiological processes. The interaction of beta-LG with FA was studied using fluorescence spectroscopy to determine the FA binding constant and mode and the influence of the protein on FA photodegradation. At < or = 20 microM FA, which may be the critical self-association concentration, the binding constant and number are 2.0 (+/-0.6) x 10(6) M(-1) and 1.30 (+/-0.03) when excited at 280 nm and 4.3 (+/-2.2) x 10(5) M(-1) and 1.17 (+/-0.04) at 295 nm, as determined by protein intrinsic fluorescence. FA binds to the surface of beta-LG, possibly in the groove between the alpha-helix and the beta-barrel. Fluorescence analysis of the pterin portion of FA shows that complexation with beta-LG improves FA photostability. It is suggested that beta-LG complexes could be used as an effective carrier of FA in functional foods.
β-乳球蛋白（β-LG）是牛乳中的主要乳清蛋白，能与多种化合物结合。叶酸（FA）是维生素 B 族的一种合成形式，也称为叶酸，是多种生理过程必需的辅因子。本研究采用荧光光谱法研究了β-LG 与 FA 的相互作用，以确定 FA 的结合常数和结合模式，以及蛋白质对 FA 光降解的影响。在≤20μM 的 FA（可能是临界自缔合浓度）下，当在 280nm 处激发时，结合常数和数量分别为 2.0（±0.6）×10^6 M^-1 和 1.30（±0.03），当在 295nm 处激发时，结合常数和数量分别为 4.3（±2.2）×10^5 M^-1 和 1.17（±0.04），这是通过蛋白质固有荧光确定的。FA 结合在β-LG 的表面上，可能结合在α-螺旋和β-桶之间的凹槽中。FA 蝶啶部分的荧光分析表明，与β-LG 复合可提高 FA 的光稳定性。因此，β-LG 复合物可用作功能性食品中 FA 的有效载体。
