Lecithins, Cephalins, and Phospholipids

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. 

Stanacev et al. (1964) have reported the synthesis of the first diether analog of a lecithin, L-a-(dioctadecyl) lecithin, and have given infrared spectra of the diether and L-a-(dioctadecanoyl) lecithin, the diester. Fontanges et al. (1964) have used thin-layer chromatography and infrared spectroscopy to identify samples of lecithin down to 22 fig. 

The effect of a dc potential applied across brain cephalin and lecithin films has been studied with infrared methods (May and Kamble, 1968). When an electric 

Abramson et al. (19646) have prepared by ultrasonication optically clear aqueous dispersions of phosphatidyl serine (PS). Infrared and titration data indicated that at the isoelectric point the molecule is a dipolar ion of phosphate and amino groups. They also found evidence for the existence of the following three forms isoelectric or acidic (XXX), HPS monosodium salt (XXXI), NaPS and disodium salt (XXXII), 

Chapman and Morrison (1966) have found NMR evidence favoring a dipolar ionic form for the phosphatidyl ethanolamines. Also, their infrared spectra of chloroform solutions favor a dipolar ionic structure. The evidence was as follows if dioleoyl-phosphatidyl ethanolamines exist in chloroform in a nonionic form, then intense bands in the 3300 cm region should occur because of NH stretching frequencies. Bands were found at 3058, 2710, 2538, and a probable band at 3021 cm , which they correlated with vibrations of an NHj group. A comparison of the spectra of dioleoyl-phosphatidyl ethanolamine and a dipolar ionic amino acid, such as alanine, showed almost identical spectra in the 4000 to 2000 cm region. The spectrum of the non-ionized compound, OL-a-alanine methyl ester in chloroform shows intense absorption in the 3300 cm region characteristic of a free primary amino group. 

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