Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA.
School of Pharmacy, University of Wisconsin-Madison, 777 Highland Avenue, Madison, WI 53705, USA.
Analyst. 2016 Aug 2;141(16):4863-9. doi: 10.1039/c5an00835b.
Ion mobility-mass spectrometry (IM-MS) is often employed to look at the secondary, tertiary, and quaternary structures of naked peptides and proteins in the gas-phase. Recently, it has offered a unique glimpse into proline-containing peptides and their cis/trans Xxx-Pro isomers. An experimental "signature" has been identified wherein a proline-containing peptide has its Pro residues substituted with another amino acid and the presence or absence of conformations in the IM-MS spectra is observed. Despite the high probability that one could attribute these conformations to cis/trans isomers, it is also possible that cis/trans isomers are not the cause of the additional conformations in proline-containing peptides. However, the experimental evidence of such a system has not been demonstrated or reported. Herein, we present the IM-MS analysis of Neuropeptide Y's wild-type (WT) signal sequence and Leu7Pro (L7P) mutant. Although comparison of arrival times and collision cross-sections of M + 4H ions yields the cis/trans "signature", molecular dynamics indicates that a cis-Pro7 is not very stable and that trans-Pro7 conformations of the same cross-section arise with equal frequency. We believe that this work further underscores the importance of theoretical calculations in IM-MS structural assignments.
离子淌度-质谱联用（IM-MS）常用于研究气相中裸肽和蛋白质的二级、三级和四级结构。最近，它为含有脯氨酸的肽及其顺/反 Xxx-Pro 异构体提供了独特的见解。已经确定了一个实验“特征”，其中含有脯氨酸的肽将其脯氨酸残基用另一种氨基酸取代，并观察到在 IM-MS 谱中是否存在构象。尽管很有可能将这些构象归因于顺/反异构体，但也有可能含有脯氨酸的肽中的额外构象不是顺/反异构体的原因。然而，这种系统的实验证据尚未得到证明或报道。在此，我们展示了神经肽 Y 的野生型（WT）信号序列和 Leu7Pro（L7P）突变体的 IM-MS 分析。尽管 M + 4H 离子的到达时间和碰撞截面的比较得出了顺/反“特征”，但分子动力学表明，顺式-Pro7 不太稳定，并且具有相同截面的反式-Pro7 构象以相等的频率出现。我们相信这项工作进一步强调了理论计算在 IM-MS 结构分配中的重要性。
