Ghanta Krishna Prasad, Pal Tamisra, Mondal Sandip, Bandyopadhyay Sanjoy
Molecular Modeling Laboratory, Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India.
Centre for Computational and Data Sciences, Indian Institute of Technology, Kharagpur 721302, India.
J Phys Chem B. 2020 May 14;124(19):3909-3921. doi: 10.1021/acs.jpcb.0c02001. Epub 2020 Apr 30.
We have performed molecular dynamics (MD) simulations of the protein α-lactalbumin in aqueous solution containing the ionic liquid (IL) 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF]) as the cosolvent at different concentrations. Attempts have been made to obtain quantitative understanding of the effects of the IL on the conformational features of the protein as well as the distributions of the IL and water around it. The calculations revealed enhanced rigidity of the protein with reduced conformational fluctuations and increasingly correlated local motions in the presence of the IL. Nonuniform relative population of the BMIM and BF ions at the protein surface with respect to that in the bulk solution has been observed. It is demonstrated that exchange of water by the IL around the protein results in rearrangement of the hydrogen bond network at the interface with breaking of protein-water hydrogen bonds and formation of protein-IL hydrogen bonds. Importantly, it is found that the protein forms increased number of stronger salt bridges in the presence of IL. This shows that the formation of a greater number of such stronger salt bridges is the origin behind the enhanced rigidity of the protein in the presence of the IL.
我们对蛋白质α-乳白蛋白在含有离子液体（IL）1-丁基-3-甲基咪唑四氟硼酸盐（[BMIM][BF₄]）作为不同浓度助溶剂的水溶液中进行了分子动力学（MD）模拟。已尝试定量了解离子液体对蛋白质构象特征以及其周围离子液体和水分布的影响。计算结果表明，在离子液体存在下，蛋白质的刚性增强，构象波动减小，局部运动的相关性增加。观察到蛋白质表面的BMIM和BF₄离子相对于本体溶液中的相对丰度不均匀。结果表明，蛋白质周围的离子液体与水的交换导致界面处氢键网络的重新排列，蛋白质-水氢键断裂，蛋白质-离子液体氢键形成。重要的是，发现在离子液体存在下蛋白质形成的更强盐桥数量增加。这表明形成更多这种更强的盐桥是离子液体存在下蛋白质刚性增强的背后原因。
