ABSTRACT
Mild alkaline hydrolysis and phase separation by adding chloroform gives an aqueous phase containing phosphate esters from all the diacyl phospholipids. Phosphate determinations on the various phases give: total diacyl phospholipid, plasmalogens; and sphingomyelin plus alkyl ether phospholipids. The inositol-containing phospholipids, phosphatidylinositol, phosphatidylinositol 4-phosphate and phosphatidylinositol 4,5-bisphosphate are known to be of considerable importance in relation to receptors and second messengers. Activation of various cell surface receptors leads via a G-protein to phospholipase C hydrolysis of phosphatidylinositol 4,5-bisphosphate, releasing inositol 1,4,5-trisphosphate and diacylglycerol. Plant chloroplast membranes contain sulfoquinovosyldiacylglycerol, quinovose being 6-deoxy-glucose. Sphingolipids containing a sulfonic acid residue have been found in marine diatoms and certain bacteria. Extraction with chloroform-methanol followed by TLC and autoradiography will show up any sulfolipids. Various spray reagents detect sugar-containing sulfolipids and there is also a spectrophotometry assay for cerebroside sulfate, based on formation of a colored complex with the cationic dye azure A.
