Karki Santosh, Flanigan Paul M, Perez Johnny J, Archer Jieutonne J, Levis Robert J
Department of Chemistry and Center for Advanced Photonics Research, Temple University, Philadelphia, PA, 19122, USA.
J Am Soc Mass Spectrom. 2015 May;26(5):706-15. doi: 10.1007/s13361-015-1084-3. Epub 2015 Mar 10.
Femtosecond (fs) laser vaporization is used to transfer cytochrome c, myoglobin, lysozyme, and ubiquitin from the condensed phase into an electrospray (ES) plume consisting of a mixture of a supercharging reagent, m-nitrobenzyl alcohol (m-NBA), and trifluoroacetic acid (TFA), acetic acid (AA), or formic acid (FA). Interaction of acid-sensitive proteins like cytochrome c and myoglobin with the highly charged ES droplets resulted in a shift to higher charge states in comparison with acid-stable proteins like lysozyme and ubiquitin. Laser electrospray mass spectrometry (LEMS) measurements showed an increase in both the average charge states (Zavg) and the charge state with maximum intensity (Zmode) for acid-sensitive proteins compared with conventional electrospray ionization mass spectrometry (ESI-MS) under equivalent solvent conditions. A marked increase in ion abundance of higher charge states was observed for LEMS in comparison with conventional electrospray for cytochrome c (ranging from 19+ to 21+ versus 13+ to 16+) and myoglobin (ranging from 19+ to 26+ versus 18+ to 21+) using an ES solution containing m-NBA and TFA. LEMS measurements as a function of electrospray flow rate yielded increasing charge states with decreasing flow rates for cytochrome c and myoglobin.
飞秒（fs）激光汽化用于将细胞色素c、肌红蛋白、溶菌酶和泛素从凝聚相转移到由增压试剂间硝基苄醇（m-NBA）与三氟乙酸（TFA）、乙酸（AA）或甲酸（FA）的混合物组成的电喷雾（ES）羽流中。细胞色素c和肌红蛋白等酸敏感蛋白与高电荷ES液滴的相互作用导致与溶菌酶和泛素等酸稳定蛋白相比，电荷态向更高值转变。激光电喷雾质谱（LEMS）测量表明，在等效溶剂条件下，与传统电喷雾电离质谱（ESI-MS）相比，酸敏感蛋白的平均电荷态（Zavg）和强度最大的电荷态（Zmode）均有所增加。使用含有m-NBA和TFA的ES溶液，与传统电喷雾相比，LEMS观察到细胞色素c（19+至21+，而传统电喷雾为13+至16+）和肌红蛋白（19+至26+，而传统电喷雾为18+至21+）的高电荷态离子丰度显著增加。作为电喷雾流速函数的LEMS测量结果显示，细胞色素c和肌红蛋白的电荷态随流速降低而增加。
