Schwartz Andrew J, Shelley Jacob T, Walton Courtney L, Williams Kelsey L, Hieftje Gary M
Department of Chemistry , Indiana University , Bloomington , IN 47405 , USA . Email:
Department of Chemistry and Biochemistry , Kent State University , Kent , OH 44242 , USA.
Chem Sci. 2016 Oct 1;7(10):6440-6449. doi: 10.1039/c6sc02032a. Epub 2016 Jun 27.
Modern "-omics" (, proteomics, glycomics, metabolomics, ) analyses rely heavily on electrospray ionization and tandem mass spectrometry to determine the structural identity of target species. Unfortunately, these methods are limited to specialized mass spectrometry instrumentation. Here, a novel approach is described that enables ionization and controlled, tunable fragmentation of peptides at atmospheric pressure. In the new source, a direct-current plasma is sustained between a tapered metal rod and a flowing sample-containing solution. As the liquid stream contacts the electrical discharge, peptides from the solution are volatilized, ionized, and fragmented. At high discharge currents (, 70 mA), electrospray-like spectra are observed, dominated by singly and doubly protonated molecular ions. At lower currents (35 mA), many peptides exhibit extensive fragmentation, with a-, b-, c-, x-, and y-type ion series present as well as complex fragments, such as d-type ions, not previously observed with atmospheric-pressure dissociation. Though the mechanism of fragmentation is currently unclear, observations indicate it could result from the interaction of peptides with gas-phase radicals or ultraviolet radiation generated within the plasma.
现代的“组学”（蛋白质组学、糖组学、代谢组学等）分析严重依赖电喷雾电离和串联质谱来确定目标物种的结构特性。不幸的是，这些方法仅限于专门的质谱仪器。在此，描述了一种新方法，该方法能够在大气压下实现肽的电离以及可控的、可调谐的碎片化。在新的离子源中，在一根锥形金属棒和流动的含样品溶液之间维持直流等离子体。当液流接触放电时，溶液中的肽会挥发、电离并碎片化。在高放电电流（例如70 mA）下，观察到类似电喷雾的光谱，主要由单质子化和双质子化分子离子主导。在较低电流（35 mA）下，许多肽表现出广泛的碎片化，存在a-、b-、c-、x-和y-型离子系列以及复杂的碎片，如d-型离子，这是以前在大气压解离中未观察到的。尽管目前碎片化的机制尚不清楚，但观察结果表明，这可能是肽与等离子体内产生的气相自由基或紫外线辐射相互作用的结果。
