Molecular species analysis of lipids by metastable ion mass spectrometry

Lipid composition of the gram-negative, budding, seawater bacterium Hyphomonas jannaschiana lacking in phospholipids

The extractable polar lipids of the gram-negative, budding, seawater bacterium Hyphomonas jannaschiana VP-2T were shown to consist of five glycolipids, namely, 1,2-diacyl-3-alpha-D-glucopyranosyl-sn-glycerol (I) (25% of the total lipids), 1,2-diacyl-3-alpha-D-glucuronopyranosyl-sn-glycerol (II) (41%), taurine-amide of II (III) (32%), acyl-D-glucuronopyranoside (IV) (0.9%), and acyl-3-O-acyl-D-glucuronopyranoside (V) (0.4%); glycolipid (III) was described by the authors previously. In addition, small amounts of poly(beta-hydroxybutyrate) and free fatty acids were present in the lipids extracted. Neither phospholipids nor low-polarity lipids, such as fatty acid esters of glycerol or fatty alcohols, were detected. Glycolipids I, II, IV, V were isolated in chromatographically pure state by chromatography on DEAE-cellulose and silica-gel columns. Their structures were established using chromatographic, spectrometric and chemical-degradation methods. In glyceroglycolipids I and II, unsaturated fatty acid residues were located predominantly at the sn-1 carbon of the glycerol moiety while saturated ones were linked mainly to the sn-2 carbon.

FAB MS/MS for phosphatidylinositol, -glycerol, -ethanolamine and other complex phospholipids

Fast atom bombardment (FAB) of phosphatidylinositol, phosphatidylethanolamine, cardiolipin, phosphatidic acid and phosphatidylglycerol produces a limited number of very informative negative ions. Especially significant is the formation of (M-H)-ions and ions that correspond to the carboxylate portions of these molecules. FAB desorption in combination with collisional activation allows for characterization of fragmentation and determination of structural features. Collisional activation of the carboxylate anion from complex lipids is especially informative. Structural characterization of the fatty acids can be achieved as the released saturated carboxylate anions undergo highly specific charge remote fragmentations that are entirely consistent with the chemistry of carboxylate anions desorbed from free fatty acids. This permits both identification of the modification and assignment of its location on the acid chain. FAB-desorbed alkyl acetyl glycerophosphocholines (platelet-activating factor) do not produce (M-H)-ions. However, significant high mass ions are formed, and these can be collisionally activated for structural characterization.