Luxembourg Stefan L, McDonnell Liam A, Duursma Marc C, Guo Xinghua, Heeren Ron M A
FOM Institute for Atomic and Molecular Physics, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands.
Anal Chem. 2003 May 15;75(10):2333-41. doi: 10.1021/ac026434p.
Intense intact molecular ion signals have been obtained from phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidyiinositol using matrix-enhanced secondary ion mass spectrometry (ME-SIMS). It was found that the high-mass (m/z >500) regions of the ME-SIMS spectra closely resembled those obtained using matrix-assisted laser desorption/ionization (MALDI). Using high spatial resolution SIMS, a detailed investigation of dried-droplet samples was performed. Based on the detected Na+ and 2,5-DHB matrix signal intensities, different crystal types were distinguished, in addition to different sizes of crystals. Spatially mapping the pseudomolecular and fragment ions of the phospholipids revealed that the nature of the pseudomolecular ions formed, as well as the ratio of intact molecular to fragment ion, was dependent on the type and surface composition of the crystal. The observed chemical bias effects due to crystal heterogeneity and the resulting variation in desorption/ionization efficiency will complicate the interpretation of data obtained from matrix-assisted mass spectrometric (imaging) techniques and is an important factor in the "hot spot" phenomenon frequently encountered in MALDI experiments. In this respect, imaging SIMS was found to be a versatile tool to investigate the effects of the local physicochemical conditions on the detected molecular species.
使用基质增强二次离子质谱（ME-SIMS）已从磷脂酰胆碱、磷脂酰乙醇胺、磷脂酰甘油和磷脂酰肌醇中获得了强烈的完整分子离子信号。研究发现，ME-SIMS光谱的高质量（m/z>500）区域与使用基质辅助激光解吸/电离（MALDI）获得的区域非常相似。使用高空间分辨率SIMS对干滴样品进行了详细研究。除了不同尺寸的晶体外，基于检测到的Na+和2,5-DHB基质信号强度，区分了不同的晶体类型。对磷脂的准分子离子和碎片离子进行空间映射显示，形成的准分子离子的性质以及完整分子与碎片离子的比例取决于晶体的类型和表面组成。由于晶体异质性导致的化学偏倚效应以及由此产生的解吸/电离效率变化，将使从基质辅助质谱（成像）技术获得的数据解释复杂化，并且是MALDI实验中经常遇到的“热点”现象的一个重要因素。在这方面，成像SIMS被发现是研究局部物理化学条件对检测到的分子种类影响的一种通用工具。
