alpha-d-glucopyranosyl-, d-alanyl- and l-lysylcardiolipin from gram-positive bacteria: analysis by fast atom bombardment mass spectrometry.

Cardiolipin species substituted on O2 of the middle glycerol moiety with alpha-d-glucopyranosyl, d-alanyl and l-lysyl residues were isolated from different gram-positive bacteria. There respective structures were elucidated by positive and negative mode fast atom bombardment mass spectrometry. The structural heterogeneity due to different fatty acid combinations was documented by up to seven molecular ions. General structural features were derived from diagnostic fragment ions, generated by single cleavage at the phosphodiester moieties in both positive and negative ion mode. A diagnostically important fragment ion for d-alanylcardiolipin was observed in the positive ion mode. It arose from double cleavage of the phosphodiester moieties yielding [NaH(Na) PO4-CH2.CH(OCO.CHNH2.CH3) CH2+]+. The fatty acid combinations in the phosphatidyl and diacylglycerol ions make it possible to recognize whether saturated and unsaturated fatty acids were selectively or randomly distributed on the two positions of the glycerol moieties. Molecular structures of cardiolipins, derived from mass spectrometric experiments, are in full agreement with those, elucidated by classical chemical analyses.