Collision-Induced Dissociation of Electrosprayed NaCl Clusters: Using Molecular Dynamics Simulations to Visualize Reaction Cascades in the Gas Phase
详细信息 查看全文
- 作者：Tilo D. Schachel ; Haidy Metwally ; Vlad Popa…
- 关键词：Reaction mechanism ; Salt cluster ; Transition state ; Charged residue model ; Magic number
- 刊名：Journal of The American Society for Mass Spectrometry
- 出版年：2016
- 出版时间：November 2016
- 年：2016
- 卷：27
- 期：11
- 页码：1846-1854
- 全文大小：2,025 KB
- 刊物主题：Analytical Chemistry; Biotechnology; Organic Chemistry; Proteomics; Bioinformatics;
- 出版者：Springer US
- ISSN：1879-1123
- 卷排序：27
文摘
Infusion of NaCl solutions into an electrospray ionization (ESI) source produces [Na(n+1)Cln]+ and other gaseous clusters. The n = 4, 13, 22 magic number species have cuboid ground state structures and exhibit elevated abundance in ESI mass spectra. Relatively few details are known regarding the mechanisms whereby these clusters undergo collision-induced dissociation (CID). The current study examines to what extent molecular dynamics (MD) simulations can be used to garner insights into the sequence of events taking place during CID. Experiments on singly charged clusters reveal that the loss of small neutrals is the dominant fragmentation pathway. MD simulations indicate that the clusters undergo extensive structural fluctuations prior to decomposition. Consistent with the experimentally observed behavior, most of the simulated dissociation events culminate in ejection of small neutrals ([NaCl]i, with i = 1, 2, 3). The MD data reveal that the prevalence of these dissociation channels is linked to the presence of short-lived intermediates where a relatively compact core structure carries a small [NaCl]i protrusion. The latter can separate from the parent cluster via cleavage of a single Na-Cl contact. Fragmentation events of this type are kinetically favored over other dissociation channels that would require the quasi-simultaneous rupture of multiple electrostatic contacts. The CID behavior of NaCl cluster ions bears interesting analogies to that of collisionally activated protein complexes. Overall, it appears that MD simulations represent a valuable tool for deciphering the dissociation of noncovalently bound systems in the gas phase.