Studies on phospholipids. 2. 2:4-Dinitrophenylkephalins

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Abstract
Diazom ethane reacts with dinitrophenylcephalins to form the corresponding methyl esters, while lecithin is unaffected. By chromatography or countercurrent distribution the following methylated dinitrophenylcephalin fractions could be distinguished: (1) material with [lambda] max at 328 m[mu], which consisted of a mixture of the methyl esters of dinitrophenylphosphatidylethanolamine, dinitrophenylphosphatidylserine and of the corresponding dinitrophenyl-acetal phospholipids; (2) material with [lambda] max at 345 m[mu], in which the atomic ratio dinitrophenyl groups: P was 0.5; (3) material with [lambda] max at 355 mu, which was obtained only from egg-yolk phospholipids and which was a minor component. Evidence is presented showing that the fraction of the methylated dinitrophenylcephalin with [lambda] max at 345 m[mu] was unaffected by further treatment with diazom ethane. More material giving rise to the dinitrophenylcephalin fraction with [lambda] max at 345 m[mu] was present in the ethanol-soluble fraction of egg-yolk phospholipids compared with the ethanol-insoluble portion. After the in vitro incorporation of P32, the relative specific radioactivity of the phosphorus associated with the dinitrophenylcephalin with [lambda] max at 345 m[mu][mu] was much greater than that of either the dinitrophenylcephalin with [lambda] max at 328 m[mu] or the choline phospholipids. It is concluded that the methylated dinitrophenylcephalins with max at 345 m[mu] and at 355 m[mu] represent hitherto unrecognized forms of cephalin. Procedures are described both for the determination of these forms of cephalin and for their separation from each other and from choline-containing phospholipids.