Kaltashov I A, Fenselau C
Department of Chemistry and Biochemistry, University of Maryland Baltimore County 21250, USA.
Proteins. 1997 Feb;27(2):165-70. doi: 10.1002/(sici)1097-0134(199702)27:2<165::aid-prot2>3.0.co;2-f.
The stability of the alpha helix as an element of secondary structure is examined in the absence of solvation, in the gas phase. Mass-analyzed ion kinetic energy (MIKE) spectrometry was applied to measure intercharge repulsion and intercharge distance in multiply protonated melittin, a polypeptide known to possess a stable helical structure in a number of different environments. The experimental results, interpreted in combination with molecular mechanics calculations, suggest that triply charged melittin retains its secondary structure in the gas phase. The stability if the alpha-helical conformation of the polypeptide in the absence of solvent molecules reflects the fact that a network of intrinsic helical hydrogen bonds is energetically more favorable than unfolded conformations.
在气相中，在没有溶剂化作用的情况下，研究了作为二级结构元件的α螺旋的稳定性。采用质量分析离子动能（MIKE）光谱法测量了多重质子化蜂毒素中的电荷间排斥力和电荷间距离，蜂毒素是一种在许多不同环境中都具有稳定螺旋结构的多肽。结合分子力学计算对实验结果进行解释，结果表明三电荷蜂毒素在气相中保留了其二级结构。在没有溶剂分子的情况下，多肽α螺旋构象的稳定性反映了这样一个事实，即内在螺旋氢键网络在能量上比未折叠构象更有利。
