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Direct Analysis of Proteins from Solutions with High Salt Concentration Using Laser Electrospray Mass Spectrometry
Journal of the American Society for Mass Spectrometry ( IF 3.2 ) Pub Date : 2018-03-08 , DOI: 10.1007/s13361-018-1893-2
Santosh Karki 1 , Fengjian Shi 1 , Jieutonne J. Archer 1 , Habiballah Sistani 1 , Robert J. Levis 1
Affiliation  

The detection of lysozyme, or a mixture of lysozyme, cytochrome c, and myoglobin, from solutions with varying salt concentrations (0.1 to 250 mM NaCl) is compared using laser electrospray mass spectrometry (LEMS) and electrospray ionization-mass spectrometry (ESI-MS). Protonated protein peaks were observed up to a concentration of 250 mM NaCl in the case of LEMS. In the case of ESI-MS, a protein solution with salt concentration > 0.5 mM resulted in predominantly salt-adducted features, with suppression of the protonated protein ions. The constituents in the mixture of proteins were assignable up to 250 mM NaCl for LEMS and were not assignable above a NaCl concentration of 0.5 mM for ESI. The average sodium adducts (< n >) bound to the 7+ charge state of lysozyme for LEMS measurements from salt concentrations of 2.5, 25, 50, and 100 mM NaCl are 1.71, 5.23, 5.26, and 5.11, respectively. The conventional electrospray measurements for lysozyme solution containing salt concentrations of 0.1, 1, 2, and 5 mM NaCl resulted in < n > of 2.65, 6.44, 7.57, and 8.48, respectively. LEMS displays an approximately two orders of magnitude higher salt tolerance in comparison with conventional ESI-MS. The non-equilibrium partitioning of proteins on the surface of the charged droplets is proposed as the mechanism for the high salt tolerance phenomena observed in the LEMS measurements.

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中文翻译:

使用激光电喷雾质谱法直接分析高盐浓度溶液中的蛋白质

使用激光电喷雾质谱(LEMS)和电喷雾电离质谱(ESI-MS)比较了盐浓度(0.1至250 mM NaCl)变化的溶液中溶菌酶或溶菌酶,细胞色素c和肌红蛋白的混合物的检测)。在LEMS的情况下,观察到质子化的蛋白峰直至浓度为250 mM NaCl。在ESI-MS的情况下,盐浓度> 0.5 mM的蛋白质溶液主要产生加盐特征,并抑制质子化的蛋白质离子。对于LEMS,蛋白质混合物中的成分最多可分配250 mM NaCl,而对于ESI,高于0.5 mM的NaCl浓度则不能分配。平均钠加合物(<  n >)在2.5、25、50和100 mM NaCl的盐浓度下与LEMS测量的溶菌酶的7+电荷状态结合,分别为1.71、5.23、5.26和5.11。对盐浓度为0.1、1、2和5 mM NaCl的溶菌酶溶液进行常规电喷雾测量,结果 n 分别为2.65、6.44、7.57和8.48。与传统的ESI-MS相比,LEMS的耐盐性大约高两个数量级。蛋白质在带电液滴表面的非平衡分配被认为是在LEMS测量中观察到的高耐盐性现象的机理。

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更新日期:2018-03-08
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