Structures and stabilities of small gas-phase ions

这个项目涉及多肽的基础化学。多肽是由氨基酸组成的小分子，氨基酸是蛋白质的组成部分。氨基酸的组合方式决定了蛋白质的结构及其生物学功能。我们用酶将蛋白质分解成多肽来确定氨基酸的序列。我研究质子化肽的结构以及它们如何在质谱仪中分解。氨基酸残基通常从质子化肽的一端丢失。这使得从形成的片段中识别肽（以及由此衍生的蛋白质）成为可能。当线性中间离子通过循环离子重新排列，然后重新打开到不同的线性离子时，问题就出现了。这将导致不正确的序列信息。在本提案中，我将使用质谱，分子建模和红外光谱的组合来检查质子化肽碎片中形成的不寻常离子的结构。理论将提供对这些离子碎片和/或重新排列的机制的见解。

This project involves fundamental chemistry of peptides. Peptides are small molecules composed of amino acids, the building blocks of proteins. How amino acids are combined defines the structure of a protein and its biological function. We determine the sequence of amino acids using an enzyme to break the protein into peptides. I study the structures of protonated peptides and how they break apart in a mass spectrometer. Amino acid residues are usually lost from one end of a protonated peptide. This makes it possible to identify a peptide (and hence the protein from which it was derived) from the fragments formed. Problems arise when linear intermediate ions rearrange via cyclic ions and then reopen to different linear ions. This leads to incorrect sequence information. In this proposal, I will examine the structures of unusual ions formed in the fragmentation of protonated peptides using a combination of mass spectrometry, molecular modeling and infrared spectroscopy. Theory will provide insights into mechanisms by which these ions fragment and/or rearrange.