STRUCTURAL CHARACTERIZATION OF PHOSPHATIDYL-MYO-INOSITOL MANNOSIDES FROM

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。子项目和 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以在其他 CRISP 条目中表示。列出的机构是 对于中心来说，它不一定是研究者的机构。 描述了单酰基-PIM（三酰基化PIM）和二酰基-PIM（四酰基化PIM）结构表征的多级离子阱质谱方法，即分别由一个或两个附加到糖苷上的脂肪酸取代基组成的PIM（二酰基化PIM）。虽然甘油主链上脂肪酸取代基的分配和确认可以通过前一篇文章中描述的方法轻松实现，但糖苷部分的身份及其酰化状态可以通过观察单酰基-PIM和二酰基-PIM的MS2谱中二酰基甘油部分（[M - H - 二酰基甘油]-）裂解产生的显着酰基糖苷离子来确定。 2-O-甘露糖苷（即 R3CO2H）上的脂肪酸取代基与肌醇（即 R4CO2H）上的脂肪酸取代基的区别是基于这样的发现：[M - H - 二酰基甘油]- 的 MS3 谱包含因 2-O-甘露糖苷（即 [M - H - 二酰基甘油 - R3CO2H]-离子）；而因肌醇上脂肪酸取代基丢失而产生的离子（即[M - H - 二酰基甘油 - R4CO2H]-离子）丰度较低。肌醇上的脂肪酰基部分也可以通过 [M - H - 二酰基甘油 R3CO2H]- 离子的 MS4 的产物离子谱来识别，这会产生与 R4CO2H 损失相对应的显着离子。在MS2光谱中还观察到[M-H-酰基甘露糖]-离子，因此可以确认连接至2-O-甘露糖苷的脂肪酸取代基的身份。从 MS2、MS3 和 MS4 的多级产物离子谱中获得的组合信息允许对从牛分枝杆菌卡介苗中分离的混合物中单酰基-PIM 和二酰基-PIM 的复杂结构进行分配。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The multiple-stage ion-trap mass spectrometric approaches towards to the structural characterization of the monoacyl-PIM (triacylated PIM) and the diacyl-PIM (tetracylated PIM), namely, the PIM (diacylated PIM) consisting of one or two additional fatty acid substituents attached to the glycoside, respectively, were described. While the assignment and confirmation of the fatty acid substituents on the glycerol backbone can be easily achieved by the methods described in the previous article, the identity of the glycoside moiety and its acylation state can be determined by the observation of a prominent acylglycoside ion arising from cleavage of the diacylglycerol moiety ([M - H - diacylglycerol]-) in the MS2 spectra of monoacyl-PIM and diacyl-PIM. The distinction of the fatty acid substituents on the 2-O-mannoside (i.e, R3CO2H) from that on the inositol (i.e., R4CO2H) is based on the findings that the MS3 spectrum of [M - H - diacylglycerol]- contains a prominent ion arising from further loss of the fatty acid at the 2-O-mannoside (i.e, the [M - H - diacylglycerol - R3CO2H]- ion); while the ion arising from loss of the fatty acid substituent at the inositol (i.e, the [M - H - diacylglycerol - R4CO2H]- ion) is of low abundance. The fatty acyl moiety on the inositol can also be identified by the product-ion spectrum from MS4 of the [M - H - diacylglycerol R3CO2H]- ion, which gives rise to a prominent ion corresponding to loss of R4CO2H. An [M - H - acylmannose]- ion was also observed in the MS2 spectra and thus, the identity of the fatty acid substituent attached to 2-O-mannoside can be confirmed. The combined information obtained from the multiple-stage product-ion spectra from MS2, MS3, and MS4 permit the assignment of the complex structures of monoacyl-PIMs and diacyl-PIMs in a mixture isolated from M. bovis Bacillus Calmette Guerin.