Studies on the molecular structure of rat liver cardiolipin

Rat liver cardiolipin, isolated by silicic acid column chromatography, has been resolved into five subfractions by discontinuous gradient elution from a silicic acid column. Comparison of these lipids with authentic beef heart cardiolipin established theis essential identity; the beef heart lipid differed only in having a more unsaturated fatty acid composition. A comparison between the five subfractions with regard to phosphorus and amino nitrogen content, ester/phosphorus ratios, fatty acid composition, infrared spectra, presence of salt forms, extent of peroxidation, component glycerphosphoric esters, and hydrolysis characteristics failed to explain the molecular basis for the fractionation. The presence of a free hydroxyl group in cardiolipin could not be confirmed by accetylation or acetonation. These observations were not consistent with the generally accepted diphosphatidyl glycerol structure for cardiolipin and lead to consideration of some additional possibilities.