低碰撞能量下Na离子对多肽气相裂解的影响

发布时间：2018-04-26 13:03

本文选题：串联质谱 + 多肽碎裂　；参考：《吉林大学》2017年硕士论文

【摘要】：Na离子作为常见的电荷载体,在电喷雾质谱分析中极易被检测,对多肽的碎裂有明显的影响。与经典的质子化肽的“移动质子”模型相比,Na离子加和肽的碎裂更倾向于电荷远程控制作用。本文通过碰撞诱导解离(collision induced dissociation,CID)碎裂实验和量子化学计算研究了特定氨基酸组成的多肽在H+加和与Na~+加和下的碎裂差异,目的是探究Na~+在电荷远程控制作用的过程中对多肽的气相结构和反应路径的影响。本文实验共分为三个部分:(1)谷氨酰胺作为天然易变的氨基酸,在多种生命活动中扮演着重要的角色。通过对C端为谷氨酰胺的多肽进行质谱的碎裂研究,我们首次观察和验证了谷氨酰胺残基丢失NH3产生戊二酸酐结构的bn*离子及其进一步丢失CO的现象。与质子化的碎裂对比,发现位于多肽C端的谷氨酰胺在钠加和下更具有活性,更易被多肽的C端-COOH亲核进攻丢失NH3和发生进一步的碎裂。通过量子化学计算,解释了H+加和与Na~+加和下的碎裂差异。(2)研究了不含酸碱性残基的非极性肽LAXA(X=Gly,Ala,Val,Leu,Ile和Phe)的碎裂,以对比H+加和与Na~+加和下的差异。当与H+结合时,串联质谱图中y2/b2的离子峰强比与Xxx残基有关。量子化学计算结果表明,多肽的质子亲和力与残基Xxx结构成线性关系。当有Na~+参与时,Xxx残基N端的酰胺键更易发生断裂,产生了少见的[H-Xxx-OH+Na]+。通过量子化学计算,探究了[H-Xxx-OH+Na]+中的金属-π相互作用。(3)研究了N端为Lys的多肽在碰撞诱导解离模式下的碎裂。考虑到N端的Lys残基由于较强的质子亲和力可结合质子,而碱金属可作为离子化C端的配体,本文研究了[M+H+Cat]2+的碎裂,观察到了单质子化下不易检测到的yn离子,并结合量子化学计算解释了不同碱金属阳离子(Li,Na,K)对碎裂行为的影响。
[Abstract]:As a common charge carrier, Na ion is easy to be detected in electrospray mass spectrometry (ESI) and has an obvious effect on the fragmentation of polypeptides. Compared with the "moving proton" model of the classical protonated peptide, the addition of Na + and the fragmentation of the peptide are more inclined to charge remote control. In this paper, the fragmentation differences of polypeptides with specific amino acid composition under the sum of H and Na ~ + have been studied by collision-induced dissociation induced splitting experiments and quantum chemical calculations. The aim of this study was to investigate the effect of Na ~ ~ on the gas phase structure and reaction pathway of polypeptides during the process of charge remote control. The experiment consists of three parts: 1) glutamine, as a natural variable amino acid, plays an important role in many life activities. Based on the fragmentation of C-terminal glutamine peptides, we observed and verified for the first time the production of glutaric anhydride ion by NH3 and the further loss of CO. Compared with the protonation fragmentation, it was found that the glutamine at the C-terminal of the polypeptide was more active under the addition of sodium, and was more susceptible to the loss of NH3 and further fragmentation by the nucleophilic attack of the C-COOH terminal of the peptide. By means of quantum chemistry calculation, the fragmentation difference between H + and Na ~ + is explained. The fragmentation of nonpolar peptides LAXAZOXYL ALAA ALALYL VALALEL and PHE without acid and alkaline residues are studied in order to compare the difference between H + sum and Na ~ + addition under Ile and Phe. the results are as follows: (1) the difference between H + and Na ~ + addition is compared with that of Na- + in the presence of H + and Na ~ +. When combined with H, the ratio of ion peak strength of y2/b2 in tandem mass spectrometry is related to the Xxx residue. The results of quantum chemistry show that the proton affinity of polypeptide is linear with the Xxx structure of residue. When Na ~ + is involved, the N-terminal amide bond of the xxx residue is more prone to fracture, resulting in the rare [H-Xxx-OH Na]. In this paper, the metal-蟺 interaction in [H-Xxx-OH Na] is investigated by quantum chemical calculation. The fragmentation of N-terminal polypeptides with Lys in collision-induced dissociation mode is investigated. Considering that the N-terminal Lys residue can bind to protons because of its strong proton affinity, and that alkali metals can be used as ligands for ionization of C-terminal, the fragmentation of [M H Cat] _ 2 has been studied, and the yn ions which are difficult to detect under single protonation have been observed. The effects of different alkaline-metal cations on the fragmentation behavior were explained by quantum chemical calculations.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O629.72;O657.63

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