Hsu Fong-Fu, Turk John, Shi Yixin, Groisman Eduardo A
Department of Internal Medicine, Washington University School of Medicine, St Louis, Missouri 63110, USA.
J Am Soc Mass Spectrom. 2004 Jan;15(1):1-11. doi: 10.1016/j.jasms.2003.08.006.
Acylphosphatidylglycerol (Acyl-PG), a polar lipid class containing three fatty acyl groups, was isolated from Salmonella bacteria and characterized by tandem quadrupole and quadrupole ion-trap mass spectrometric methods with electrospray ionization. The structural characterization of the acyl-PG with various acyl groups (A-B/C-PG, where A not equal B not equal C) is based on the findings that the carboxylate anions (R(x)CO(2)(-)) arising from sn-2 (R(2)CO(2)(-)) is more abundant than that arising from sn-3' (R(3')CO(2)(-)), which is much more abundant than that arising from sn-1 (R(1)CO(2)(-)). This information provides a simple method for determination of the fatty acyl moieties and their positions in the molecule. The structural identification of the molecule can also be achieved by the findings that the fragment ion reflecting the ketene loss at sn-2 is more prominent than that reflecting the acid loss (i.e., M - H - R'(2)CH=CO > M - H - R(2)CO(2)H), while the ion arising from acid loss at sn-1 or sn-3' is, respectively, more abundant than the corresponding ketene loss (i.e., M - H - R(1)CO(2)H > M - H - R'(1)CH=CO; M - H - R(3')CO(2)H > M - H -R'(3')CH=CO). The identity of the acyl moiety at sn-3' can be confirmed by an acyl-glycerophosphate anion observed in the product-ion spectrum obtained with a triple-stage quadrupole (TSQ) instrument, but not in that obtained with an ion-trap mass spectrometer (ITMS). However, the MS(2)-spectrum obtained with an ITMS is featured by the ion series that abundances of M - H - R'(2)CH=CO - R(3)CO(2)H - 74 > M - H - R'(2)CH=CO - R(1)CO(2)H - 74 z.Gt; M - H - R'(1(or 3'))CH=CO - R(3'(or 1))CO(2)H - 74. This information also facilitates structural elucidation of the acyl-PG subclass that contains various acyl substituents. Structural identifications of molecular species having two identical fatty acyl substituents at sn-1, sn-2, or sn-3' or consisting of more than one isomeric structures are also demonstrated. The identities of the minor isomeric species in the molecules can be revealed by the aforementioned structural information arising from the various ion series combined.
酰基磷脂酰甘油(Acyl-PG)是一类含有三个脂肪酰基的极性脂质,从沙门氏菌中分离得到,并通过电喷雾电离串联四极杆和四极杆离子阱质谱法进行表征。具有不同酰基的酰基-PG(A-B/C-PG,其中A不等于B不等于C)的结构表征基于以下发现:sn-2位产生的羧酸根阴离子(R(x)CO(2)(-))(R(2)CO(2)(-))比sn-3'位产生的更丰富,而sn-3'位产生的又比sn-1位产生的(R(1)CO(2)(-))丰富得多。该信息提供了一种确定脂肪酰基部分及其在分子中位置的简单方法。分子的结构鉴定也可通过以下发现实现:反映sn-2位乙烯酮损失的碎片离子比反映酸损失的更突出(即M - H - R'(2)CH=CO > M - H - R(2)CO(2)H),而sn-1或sn-3'位酸损失产生的离子分别比相应的乙烯酮损失产生的离子更丰富(即M - H - R(1)CO(2)H > M - H - R'(1)CH=CO;M - H - R(3')CO(2)H > [M - H -R'(