William G. Lowrie Department of Chemical and Biomolecular Engineering, Ohio State University, Columbus, Ohio 43210, United States.
Langmuir. 2011 Nov 15;27(22):13713-8. doi: 10.1021/la203138k. Epub 2011 Oct 19.
We compare protein-protein and protein-polymer osmotic virial coefficients measured by static light scattering for aqueous solutions of lysozyme with low-molecular-weight, hydroxy-terminated (hPEG) and methyl-terminated (mPEG) poly(ethylene glycol) at two solution conditions: pH 7.0 and 0.01 M ionic strength, and pH 6.2 and 0.8 M ionic strength. We find that adding PEG to aqueous lysozyme solutions makes a net repulsive contribution to lysozyme-lysozyme interactions, independent of ionic strength and PEG end-group hydrophobicity. PEG end-group hydrophobicity has a profound effect on the magnitude of this contribution, however, at low ionic strength where mPEG-lysozyme attractive interactions become significant. The enhanced attractions promote mPEG-lysozyme preferential interactions at the expense of lysozyme self-interactions, which leads to lysozyme-lysozyme interactions that are more repulsive in the presence of mPEG. These preferential interactions also lead to the preferential exclusion of diffusable ions locally around the protein, which results in a pronounced ionic strength dependence of mPEG-mediated lysozyme-lysozyme interactions.
我们比较了通过静态光散射测量的溶菌酶在低分子量、羟基封端（hPEG）和甲基封端（mPEG）聚乙二醇水溶液中的蛋白质-蛋白质和蛋白质-聚合物渗透压系数，在两种溶液条件下：pH7.0 和 0.01M 离子强度，以及 pH6.2 和 0.8M 离子强度。我们发现，向溶菌酶水溶液中添加 PEG 会对溶菌酶-溶菌酶相互作用产生净排斥贡献，而与离子强度和 PEG 端基疏水性无关。PEG 端基疏水性对这种贡献的大小有深远的影响，然而，在低离子强度下，mPEG-溶菌酶的吸引力相互作用变得显著。增强的吸引力促进了 mPEG-溶菌酶的优先相互作用，而牺牲了溶菌酶的自相互作用，这导致 mPEG 存在时溶菌酶-溶菌酶相互作用更具排斥性。这些优先相互作用还导致可扩散离子在蛋白质周围局部优先排斥，这导致 mPEG 介导的溶菌酶-溶菌酶相互作用对离子强度具有明显的依赖性。
