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。氨基酸的结合方式决定了蛋白质的结构和生物功能。我们用一种酶将蛋白质分解成多肽，从而确定氨基酸的序列。我研究质子化多肽的结构，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。这使得有可能从形成的片段中识别出一种多肽(以及由此产生它的蛋白质)。当线性中间离子通过环状离子重新排列，然后重新开放为不同的线性离子时，问题就出现了。这会导致错误的序列信息。在这项建议中，我将结合质子化多肽、分子模拟和红外光谱来研究质子化多肽碎裂过程中形成的不寻常离子的结构。理论将为这些离子碎裂和/或重排的机制提供洞察力。

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.