荧光猝灭法和动态光散射法研究1-丙醇和2-丙醇对水溶液中 蛋白质构象的影响

应用荧光猝灭法和动态光散射技术测定牛血清白蛋白(BSA)与荧光素在正丙醇-水和异丙醇-水混合溶剂中的相互作用距离和BSA的流体动力学半径, 研究正丙醇和异丙醇对水溶液中蛋白质构象的影响. 结果显示, 正丙醇-水和异丙醇-水混合溶剂中BSA与荧光素的相互作用距离和BSA的流体动力学半径随着正丙醇和异丙醇浓度的增加而先减小后增大, 表明低浓度的正丙醇和异丙醇有利于蛋白质形成紧密的构象, 而较高浓度的正丙醇和异丙醇则破坏蛋白质的紧密构象. 试验中观察到BSA与荧光素在正丙醇-水混合溶剂中的结合距离大于同浓度的异丙醇-水混合溶剂中的结合距离, 而BSA在前者的流体动力学半径小于后者, 说明无支链的正丙醇分子易于与蛋白质的疏水基团产生较强的疏水相互作用, 而带支链的异丙醇分子的疏水性较弱, 有利于与蛋白质分子的亲水基团相互作用而积聚在蛋白质表面.

Study of Effects of 1-Propanol and 2-Propanol on the Conformation of Protein in Aqueous Solutions by Fluorescence Quenching Technique and Dynamic Light Scattering Measurements

The binding distance of fluorescein to BSA and hydrodynamic radius of BSA in 1-propanol (NPA)-water and 2-propanol (IPA)-water mixtures were determined by a fluorescence quenching technique and dynamic light scattering measurements respectively and utilized to investigate the effects of NPA and IPA on the conformation of protein in aqueous solutions. The results showed that both binding distance of fluorescein to BSA and hydrodynamic radius of BSA decreased at first and then increased with increasing concentrations of NPA and IPA, suggesting that both NPA-water and IPA-water mixtures at high concentrations destabilize the native structure of protein, whereas at low concentrations slightly stabilize the native state of protein. It was also found that the binding distance in aqueous NPA was larger than that in aqueous IPA at the same concentration, whereas the hydrodynamic radius of BSA in the former was smaller than that in the latter, indicating that the hydrophobic part of NPA with no branch worked effectively for hydrophobic interaction with the nonpolar group of protein, and that IPA had a tendency to interact with the hydrophilic groups on the surface of protein due to its relatively weak hydrophobicity.