Hebert Michael J, Russell David H
Department of Chemistry Texas A&M University College Station , Texas 77843 , United States.
J Phys Chem Lett. 2019 Mar 21;10(6):1349-1354. doi: 10.1021/acs.jpclett.9b00268. Epub 2019 Mar 8.
Guanidinium ions (GdmH) are reported to form stable complexes (GdmH/GdmH) in aqueous solution despite strong repulsive interactions between the like-charged centers. These complexes are thought to play important roles in protein folding, membrane penetration, and formation of protein dimers. Although GdmH ions are weakly hydrated, semiempirical calculations provide evidence that these like-charged complexes are stabilized by water molecules, which serve important structural and energetic roles. Specifically, water molecules bridge between the GdmH ions of GdmH/GdmH complexes as well as complexes involving the guanidinium side chains of arginine. Potential biological significances of like-charged complexes have been largely confirmed by ab initio molecular dynamics simulations and indirect experimental evidence. We report cryo-ion mobility-mass spectrometry results for the GdmH/GdmH ion pair confined in a nanodroplet- the first direct experimental observation of this like-charged complex. A second like-charged complex, described as a water-mediated complex involving GdmH and HO, was also observed.
据报道，尽管带相同电荷的中心之间存在强烈的排斥相互作用，但胍离子（GdmH）在水溶液中会形成稳定的复合物（GdmH/GdmH）。这些复合物被认为在蛋白质折叠、膜穿透和蛋白质二聚体形成中发挥重要作用。尽管GdmH离子的水合作用较弱，但半经验计算提供了证据，表明这些带相同电荷的复合物通过水分子得以稳定，水分子起到了重要的结构和能量作用。具体而言，水分子在GdmH/GdmH复合物的GdmH离子之间以及涉及精氨酸胍基侧链的复合物之间形成桥梁。带相同电荷的复合物的潜在生物学意义已通过从头算分子动力学模拟和间接实验证据得到了很大程度的证实。我们报告了限制在纳米液滴中的GdmH/GdmH离子对的低温离子淌度-质谱结果——这是对这种带相同电荷复合物的首次直接实验观察。还观察到了第二种带相同电荷的复合物，其被描述为涉及GdmH和HO的水介导复合物。
