Houjou Toshiaki, Yamatani Kotoko, Nakanishi Hiroki, Imagawa Masayoshi, Shimizu Takao, Taguchi Ryo
Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe-dori, Mizuho-ku, Nagoya City, Aichi 467-8603, Japan.
Rapid Commun Mass Spectrom. 2004;18(24):3123-30. doi: 10.1002/rcm.1737.
Analyses of molecular species of phospholipids containing choline (Ch), such as phosphatidylcholine (PC) and sphingomyelin (SM), are reported. Neutral loss scanning was applied for the selective detection of these lipids using a quadrupole-linear ion trap mass spectrometer. By using ammonium formate as an elution buffer, both PC and SM were detected as [M+HCOO]- ions in the negative ion mode. Upon collisional activation, the [M+HCOO]- adduct ions underwent facile elimination of HCO2, to yield an ion which, in turn, readily underwent collisional-induced dissociation (CID) to eliminate CH3 to yield an [M-CH3]- ion. By selecting the proper conditions for scanning for neutral loss of 60 Da (HCO2+CH3), SM species were identified separately from PCs. Further, by selection of this [M-CH3]- ion as the precursor ion, the identities of the fatty acyl chains of PC species can be effectively obtained by MS3 experiments. Furthermore, by the MS3 analyses of [M-CH3]- specifically obtained from SM molecules, identification of sphingosine or sphinganine derivatives and their N-acyl species can also be effectively obtained. This systematic analysis of PCs and SMs by conditional neutral loss scanning, with subsequent analyses by MS3, using a linear ion trap mass spectrometer in the negative ion mode, appears to be a very effective and sensitive method. Further, MS/MS in the positive ion mode at relatively low collision energy was also effective for the identification of positional specificities in individual molecular PC species from their lysoPC-related fragments. The present paper deals only with qualitative identification of individual molecular species, and the related quantitative studies are now underway.
报道了对含胆碱（Ch）的磷脂分子种类的分析，如磷脂酰胆碱（PC）和鞘磷脂（SM）。使用四极杆-线性离子阱质谱仪，采用中性丢失扫描对这些脂质进行选择性检测。通过使用甲酸铵作为洗脱缓冲液，在负离子模式下，PC和SM均被检测为[M+HCOO]-离子。碰撞激活后，[M+HCOO]-加合离子易于消除HCO2，生成一种离子，该离子又易于发生碰撞诱导解离（CID）以消除CH3，生成[M-CH3]-离子。通过选择扫描60 Da（HCO2+CH3）中性丢失的合适条件，可将SM种类与PC区分开来。此外，通过选择该[M-CH3]-离子作为前体离子，通过MS3实验可有效获得PC种类的脂肪酰链的身份。此外，通过对从SM分子特异性获得的[M-CH3]-进行MS3分析，也可有效鉴定鞘氨醇或鞘氨醇胺衍生物及其N-酰基种类。使用线性离子阱质谱仪在负离子模式下通过条件中性丢失扫描对PC和SM进行这种系统分析，随后进行MS3分析，似乎是一种非常有效和灵敏的方法。此外，在相对较低碰撞能量下的正离子模式下的MS/MS对于从其溶血磷脂相关片段鉴定单个分子PC种类中的位置特异性也很有效。本文仅涉及单个分子种类的定性鉴定，相关的定量研究正在进行中。
