Poncet-Legrand Céline, Gautier Catherine, Cheynier Véronique, Imberty Anne
UMR1083 Sciences pour l'Knologie, INRA, Université Montpellier 1, France.
J Agric Food Chem. 2007 Oct 31;55(22):9235-40. doi: 10.1021/jf071297o. Epub 2007 Sep 12.
Interactions of proline-rich proteins (PRPs) with flavan-3-ols was studied using poly(L-proline) as a model protein by means of isothermal titration calorimetry (ITC). Several parameters were varied: (i) the galloylation and B-ring trihydroxylation of the flavan-3-ols (catechin, epicatechin, epicatechin gallate, and epigallocatechin gallate) and (ii) the degree of polymerization (monomers were compared to a mixture of oligomers with average degree of polymerization of 3.85). Large differences were observed between the flavan-3-ol monomers: no enthalpy change was measured when catechin and epicatechin were titrated by poly(L-proline), whereas thermodynamic parameters were determined in the case of galloylated monomers and mixture of oligomers. Stoichiometry ranged from 1 oligomer bound for each 12 proline units to 1 galloylated monomer for each 8 or 10 proline units. Association constants were in the range of 10(4)-10(5) M(-1), indicating a relatively high affinity of galloylated flavanols toward poly(L-proline), and the coexistence of both enthalpy- and entropy-driven phenomena was suggested. Finally, the binding of grape seed tannins to proteins was shown to be a cooperative process.
采用等温滴定量热法（ITC），以聚（L-脯氨酸）作为模型蛋白，研究了富含脯氨酸的蛋白质（PRPs）与黄烷-3-醇的相互作用。改变了几个参数：（i）黄烷-3-醇（儿茶素、表儿茶素、表儿茶素没食子酸酯和表没食子儿茶素没食子酸酯）的没食子酰化和B环三羟基化，以及（ii）聚合度（将单体与平均聚合度为3.85的寡聚物混合物进行比较）。观察到黄烷-3-醇单体之间存在很大差异：用聚（L-脯氨酸）滴定儿茶素和表儿茶素时未测得焓变，而对于没食子酰化单体和寡聚物混合物则测定了热力学参数。化学计量比范围从每12个脯氨酸单元结合1个寡聚物到每8或10个脯氨酸单元结合1个没食子酰化单体。缔合常数在10⁴ - 10⁵ M⁻¹范围内，表明没食子酰化黄烷醇对聚（L-脯氨酸）具有相对较高的亲和力，并且表明存在焓驱动和熵驱动现象。最后，葡萄籽单宁与蛋白质的结合被证明是一个协同过程。
