Parmar Avanish S, Muschol Martin
Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
Biophys J. 2009 Jul 22;97(2):590-8. doi: 10.1016/j.bpj.2009.04.045.
Using static and dynamic light scattering we have investigated the effects of either strongly chaotropic, nearly neutral or strongly kosmotropic salt ions on the hydration shell and the mutual hydrodynamic interactions of the protein lysozyme under conditions supportive of protein crystallization. After accounting for the effects of protein interaction and for changes in solution viscosity on protein diffusivity, protein hydrodynamic radii were determined with +/-0.25 A resolution. No changes to the extent of lysozyme hydration were discernible for all salt-types, at any salt concentration and for temperatures between 15-40 degrees C. Combining static with dynamic light scattering, we also investigated salt-induced changes to the hydrodynamic protein interactions. With increased salt concentration, hydrodynamic interactions changed from attractive to repulsive, i.e., in exact opposition to salt-induced changes in direct protein interactions. This anti-correlation was independent of solution temperature or salt identity. Although salt-specific effects on direct protein interactions were prominent, neither protein hydration nor solvent-mediated hydrodynamic interactions displayed any obvious salt-specific effects. We infer that the protein hydration shell is more resistant than bulk water to changes in its local structure by either chaotropic or kosmotropic ions.
我们使用静态和动态光散射技术，研究了在有利于蛋白质结晶的条件下，强离液序列高的、近中性的或强促溶盐离子对蛋白质溶菌酶的水合壳层及其相互流体动力学相互作用的影响。在考虑了蛋白质相互作用的影响以及溶液粘度变化对蛋白质扩散率的影响之后，以±0.25 Å的分辨率测定了蛋白质的流体动力学半径。在15至40摄氏度之间的任何盐浓度下，对于所有盐类型，均未观察到溶菌酶水合程度的变化。结合静态和动态光散射，我们还研究了盐诱导的蛋白质流体动力学相互作用的变化。随着盐浓度的增加，流体动力学相互作用从吸引变为排斥，即与盐诱导的直接蛋白质相互作用的变化完全相反。这种反相关性与溶液温度或盐的种类无关。尽管盐对直接蛋白质相互作用的特异性效应很显著，但蛋白质水合和溶剂介导的流体动力学相互作用均未显示出任何明显的盐特异性效应。我们推断，蛋白质水合壳层比本体水更能抵抗离液序列高的离子或促溶离子对其局部结构的改变。
