L-a- cephalin

Baer, E. and Buchnea, D. (1959) Synthesis of L-a-(dioleoyl)-cephalin, with a comment on the stereochemical designation of glycerol phosphatides,./. Am. Chem. 

L-a-Phosphatidyl ethanolamine (cephalin) phospholipid commonly C7Hj2NOgP(2R) found in microorganisms, but largely absent in plants. 

Baer (1953) has recorded the spectra of pure dimyristoyl, dipalmitoyl, and distearoyl L-a-lecithins. Baer et al. (1952) have also recorded spectra of L- -cephalins, namely, the same kinds of fatty acid derivatives. The spectra have differences, although this is not true for the corresponding straight-chain fatty acids. In the region from 870 to 714 cm" several large differences occur. 

Baer and Stanacev (1964) have reported the synthesis of dipalmitoyl L-a-glyceryl (2-aminoethyl) phosphonate, the first synthesis of a complex lipid containing phosphonic acid, and have shown spectra of L-a-(dipalmitoyl)cephalin and of dipalmitoyl L-a-phosphono(deoxy)cephalin. 

This report described the synthesis of diether phosphonolipids which resemble cephalins structurally. Infrared spectra were given for dihexadecanoyl L-a-glyceryl-(-2-aminoethyl) phosphonate and dihexadecanoyl L-a-glycerylphosphorylethanola-mine. 

The above considerations lead to the conclusion that the liver should be capable of synthesizing plasma phospholipides in toto from its various components. This appears to be the case, for a purified enzyme preparar-tion of rat liver has been shown to form diacylphosphatidic acids from fatty acids and L-a-glycerophosphate. i The diacylphosphatidic acids need only a nitrogenous base in ester linkage with the phosphate to form lecithin (or a cephalin). The following mechanism was postulated for the synthesis of distearylphosphatidic acid from stearic acid-l-C and L-o-glycerophosphate-P (a-G-P) by the rat liver preparation ... 

Phosphatidylcholine (lecithin) is the most abundant phospholipid in membranes. Phosphatidylethanolamine (cephalin) has an ethanolamine residue instead of choline, and phosphatidylserine has a serine residue. In phosphatidylinositol, phosphatidate is esterified with the sugarlike cyclic polyalcohol myo-inositol. A doubly phosphorylated derivative of this phospholipid, phosphatidylinositol 4,5-bisphosphate, is a special component of membranes, which, by enzymatic cleavage, can give rise to two second messengers, diacylglycerol (DAG) and inositol l,4,5trisphosphate (InsPsi see p.386). 

P l sma ri ch n j)lajtej ejts (PRP) For plasma rich in platelets obtained by centrifugation (at 1200 revolutions/minute) of citrated fresh blood, the number of platelets was measured with a Thoma s cell and the aggregability in presence of ADP or collagen, the factor F3P and the time of cephalin kaolin (TCK) were determined. 

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