Structural Characterization of Sulfoquinovosyl, Monogalactosyl and Digalactosyl Diacylglycerols by FAB-CID-MS/MS

The glycolipids such as sulfoquinovosyl diacylglycerol (SQDG), isolated from wild-type cyanobacterium Synechocystis sp. PCC 6803, and monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG), obtained from whole wheat Ñour, have been investigated by using fast atom bombardment tandem mass spectrometry (FAB-MS/MS). Collision-induced dissociation (CID) of sodium-adduct molecular ions [M Ô H + 2Na ]‘ from SQDG and [M + Na ]‘ from MGDG and DGDG generates ions which are characteristic of the structure of the polar head group as well as the fatty acid composition. In particular, the charge-remote fragmentation along the fatty acid chains observed in the high-mass range was useful to locate the double-bond positions. The major component ion ( [M Ô H + 2Na ]‘ at m/z 865) of SQDG contains oleic and palmitic acids at the sn-1 and sn-2 positions, respectively. The predominant molecular ion ( [M + Na ]‘ at m/z 801) of MGDG contains two linoleic acids. One of the two major species of DGDG contains palmitic and linoleic acids ( [M + Na ]‘ at m/z 939) at the sn-1 and sn-2 positions, while the other contains two linoleic acids ( [M + Na ]‘ at m/z 963). The utility of FAB-MS/MS in the structural determination of glycolipids in mixtures of biological origin has been demonstrated. 1997 by ( John Wiley & Sons, Ltd.