Institute of Biophysics, Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
J Phys Chem B. 2011 Oct 20;115(41):11786-92. doi: 10.1021/jp205279k. Epub 2011 Sep 28.
Protein intermolecular depletion interactions induced by polyethylene glycol (PEG) depend largely on its concentration and molecular weight. Herein, we investigated the effects of various concentrations and molecular weights of PEG on lysozyme interactions through the analysis of protein rotational diffusion, which is susceptible to intermolecular interactions at short range. To this end, we measured fluorescence anisotropy of fluorescein-tagged lysozyme added as a tracer in concentrated native lysozyme solutions and introduced a protein concentration-dependent interaction parameter, k(rot). The results show the nonmonotonic changes in k(rot) as the concentrations of PEG10000 and 6000 are increased. The depletion attractions are characterized by the decrease in k(rot), indicating an increase of a degree at which protein rotational diffusion slows down. The influences of temperature on the lysozyme rotational diffusion and k(rot) were also measured, and the validity of this approach was checked through comparison with the colloidal theory.
聚乙二醇（PEG）引起的蛋白质分子间耗尽相互作用在很大程度上取决于其浓度和分子量。在这里，我们通过分析蛋白质旋转扩散来研究不同浓度和分子量的 PEG 对溶菌酶相互作用的影响，蛋白质旋转扩散很容易受到短程分子间相互作用的影响。为此，我们测量了荧光标记的溶菌酶的荧光各向异性，该溶菌酶作为示踪剂添加到浓缩的天然溶菌酶溶液中，并引入了一个与蛋白质浓度相关的相互作用参数 k(rot)。结果表明，随着 PEG10000 和 6000 浓度的增加，k(rot)呈非单调变化。耗尽吸引力的特征是 k(rot)的降低，这表明蛋白质旋转扩散减慢的程度增加。还测量了温度对溶菌酶旋转扩散和 k(rot)的影响，并通过与胶体理论的比较检查了这种方法的有效性。
