Hudgins R R, Mao Y, Ratner M A, Jarrold M F
Department of Chemistry, Northwestern University, Evanston, Illinois 60208 USA.
Biophys J. 1999 Mar;76(3):1591-7. doi: 10.1016/S0006-3495(99)77318-2.
High-resolution ion mobility measurements and molecular dynamics simulations have been used to probe the conformations of protonated polyglycine and polyalanine (Gly(n)H and Ala(n)H+, n = 3-20) in the gas phase. The measured collision integrals for both the polyglycine and the polyalanine peptides are consistent with a self-solvated globule conformation, where the peptide chain wraps around and solvates the charge located on the terminal amine. The conformations of the small peptides are governed entirely by self-solvation, whereas the larger ones have additional backbone hydrogen bonds. Helical conformations, which are stable for neutral Alan peptides, were not observed in the experiments. Molecular dynamics simulations for Ala(n)H+ peptides suggest that the charge destabilizes the helix, although several of the low energy conformations found in the simulations for the larger Ala(n)H+ peptides have small helical regions.
高分辨率离子迁移率测量和分子动力学模拟已被用于探测气相中质子化聚甘氨酸和聚丙氨酸（Gly(n)H和Ala(n)H⁺，n = 3 - 20）的构象。聚甘氨酸和聚丙氨酸肽的测量碰撞积分与自溶剂化球状构象一致，其中肽链围绕并溶剂化位于末端胺上的电荷。小肽的构象完全由自溶剂化决定，而较大的肽则有额外的主链氢键。在实验中未观察到对中性丙氨酸肽稳定的螺旋构象。对Ala(n)H⁺肽的分子动力学模拟表明，电荷会使螺旋不稳定，尽管在较大的Ala(n)H⁺肽模拟中发现的几个低能量构象有小的螺旋区域。
