A novel plasmal conjugate of glycosphingolipid having cationic lipid properties was isolated from the white matter of bovine brain. Linkage analysis of galactosyl residue by methylation, liquid secondary ion, and electrospray ionization mass spectrometry of intact and methylated derivatives, and by 1 H-and 13 C-NMR spectroscopy, identified the structure unambiguously as an O-acetal conjugate of plasmal to the primary hydroxyl group of glycerol and to the 6-hydroxyl group of galactosyl residue of -galactosyl 131 sphingosine (psychosine). This novel compound is hereby termed "glyceroplasmalopsychosine"; its structure is shown below.Long chain aldehydes, hexadecanal and octadecanal, with or without an olefinic double bond, are collectively called plasmal, and are known as a common component of two classes of lipid conjugates, described as follows: (i) the classically well-established phospholipid plasmalogen (1, 2), in which plasmal is conjugated as O-alk-1-enyl (vinyl ether) group to one of the hydroxyl groups of glycerol in phosphatidylethanolamine or phosphatidylcholine 1 ; (ii) the recently found novel type of glycosphingolipid (GSL) 2 in which a plasmal is conjugated to two hydroxyl groups of the galactosyl residue of galactosylsphingosine (psychosine) or galactosylceramide through cyclic acetal linkage; these were originally isolated from human brain white matter and are termed, respectively, plasmalopsychosine (PLPS) and plasmalocerebroside. Depending on the position of hydroxyl group involved in acetal linkages, 3,4-and 4,6-cyclic plasmal conjugates of PLPS and plasmalocerebroside are termed, respectively, PLPS A or B (3), and plasmalocerebroside A or B (4). More recently, a GSL having the same structure as plasmalocerebroside B (4,6-cyclic acetal) was isolated from equine brain. The orientation of the acetal chain linked to galactosyl residue through asymmetric carbon 1 of plasmal was identified as "endo" type, initially on model plasmal conjugate of methyl--galactoside (45), subsequently on 4,6-plasmalocerebroside (5). A similar 4,6-cyclic acetal conjugate of plasmal to galactosyl alkylglyceride was isolated and characterized (6). All these conjugates are characterized by typical aldehyde reaction (e.g. oxidizing Schiff's reagent to give red color, after brief acid treatment). Among them, only PLPS shows cationic properties, and can be isolated by cation-exchange chromatography on carboxymethyl (CM)-Sephadex column in organic solvent, because of its free amino group at Sph residue. Cationic lipids are rare in animal cells and tissues (see "Discussion"). PLPS has the novel effect of inducing signal transduction in neuronal cells, particularly neuritogenesis in PC12 cells without addition of nerve growth factor; i.e. PLPS mimics the effect of nerve growth factor (7). During previous studies, we noticed the presence of cationic lipids having slower TLC migration rate than PLPS in human brain (3). We therefore undertook further systematic study of cationic lipids with plasmal conjugate in bovine brain.Durin...