自建电喷雾解吸电离源（DESI）在大分子分析中的应用及离子化机理探索

自建了简易的电喷雾解吸电离源(DESI),优化了DESI源喷口的位置和角度,并将其用于常见多肽和蛋白质的分析。多肽和小质量蛋白质(<20 kDa)可以容易地从表面解吸电离,生成清晰的质谱。而牛血清白蛋白(66.4 kDa)不能产生清晰的多电荷分布的质谱,说明当前DESI源的设计可能存在一个电离的分子量上限。通过比较不同的实验条件并对比ESI-MS,发现溶剂分子的挥发过程对电荷分布以及峰宽均有显著影响,可能是由于ESI更软引起。载样表面的性质对DESI-MS的信号强度有较大影响。金表面的自组装单分子膜(SAM)相对于纯金表面有较好的绝缘性,并有助于产生较强信号,说明来自表面的电子转移(电中和)是电喷雾解吸电离过程中的一个重要因素。该文的研究有助于对DESI-MS的实验条件和载样表面的选择,同时增进了对电喷雾解吸电离机理的了解。

Application of In-house Desorption Electrospray Ionization Source in Macromolecule Analysis and Its Exploration for Ionization Mechanism

A simple DESI source was built.The experimental conditions were optimized and used in the analysis of a few common peptides and proteins.The results indicated that peptides and small proteins(<20 kDa) can be easily ionized and well-defined mass spectra were generated.However,BSA(66.4 kDa) generated a poorly defined mass spectrum,which implies that there might be a molecular weight upper limit for the current design of the DESI source.The comparison between DESI and ESI mass spectra reveals that solvent evaporation can significantly affect the charge distribution and peak width,maybe due to the fact that ESI is softer than DESI.Self-assembled monolayer(SAM) on gold surface has a higher insulation than that on bare gold surface,so SAM surface can assist the survival of ions,indicating that the electron transfer(electrical neutralization) from the surface is an important factor in the ionization process of DESI.This study will be helpful for the selections of experimental conditions and sample surfaces for DESI-MS,and enhance the understanding of the ionization mechanism of DESI.