Studies of dialkyl ether phospholipids. II. Requirement for a liquid-crystalline substrate for hydrolysis by cabbage leaf phospholipase D

The hydrolysis of 1,2-ditetradecyl-, 1,2-dihexadecyl-, and 1,2-dioctadecyk-sn-glycero-3-phosphoryl-cholines by the soluble phospholipase D (EC 3.14.4) from cabbage leaf has been compared with that of egg lecithin. When a diethyl ether – chloroform mixture was used as activator low hydrolysis rates were observed for the dialkyl ether phospholipids because of their poor solubility in diethyl ether. Under these conditions the compounds did not inhibit the hydrolysis of egg lecithin. The hydrolytic reaction appeared to take place at the solvent–water interface resulting in a gradual denaturation of the enzyme. When sodium dodecyl sulfate was used as activator faster hydrolysis was evident due in part to a reduction in mesomorphic transition temperature (Tm) revealed by differential thermal analysis. Rates of hydrolysis of the homologous dialkyl ether phospholipids were inversely proportional to their Tm values in excess water. Under conditions required for effective hydrolysis of these compounds they inhibited the hydrolysis of egg lecithin. From studies of hydrolysis rates obtained with various combinations of phosphatidylcholine and phosphatidic acid analogues it was concluded that binding of enzyme to phospholipids and their subsequent hydrolysis required both an appropriate surface charge and a gel to liquid-crystalline phase transition in the substrate.

Studies of dialkyl ether phospholipids. I. Chemical synthesis of some model compounds

The syntheses of three 1,2-dialkyl-sn-glycero-3-phosphates and one new 1,2-dialkyl-sn-glycerol are described. 1,2-Dioctadecyl-sn-glycero-3-phosphate was obtained by phosphorylation of 1,2-dioctadecyl-sn-glycerol with diphenylphosphorodichloridate and subsequent catalytic hydrogenolysis. 1,2-Dioctadecyl-sn-glycero-3-(methyl)phosphorylcholine was prepared by phosphorylation of the same dialkyl glycerol with methylphosphorodichloridate and subsequent reaction with choline iodide. 1,2-Dimethyl-sn-glycerol was prepared by treatment of 3-benzyl-sn-glycerol with methyl iodide and KOH followed by hydrogenolysis to remove the protecting group. This compound was then phosphorylated with phenylphosphorodichloridate, the product allowed to react with choline iodide, and the iodide-free product hydrogenated catalytically to yield 1,2-dimethyl-sn-glycero-3-phosphorylcholine which was characterized as the cadmium chloride complex. Some improvements in an established synthesis of 1,2-dioctadecyl-sn-glycerol are described.

Axonal outgrowth and cell migration in vitro from nervous system of cockroach embryos

Brain and ganglia of embryonic Periplaneta americana were grown for 2 to 3 weeks in a chemically defined medium. Nerve fibers sprouted vigorously from intact brains and ganglia, interconnecting nerve cultures, and adjacent cultures of the digestive tract, Glia, tracheal, and nerve cells were present in large numbers in the migratory zone surrounding the explants.