Reversed - phase partithn thin - layer chromatography of rat liver

A PREVIOUS COMMUNICATION described the separation of rat liver lecithin into four main fractions by TLC on silica gel plates impregnated with silver nitrate (1). GLC analysis revealed that approximately 50% of the fatty acids in each of the four fractions, here designated as A, B, C, and D, was made up of two saturated fatty acids, viz., palmitic and stearic. In fraction A the remaining 50% consisted mainly of oleic acid, in fractions B, C, and D of linoleic, arachidonic, and docosahexaenoic acid, respectively. According to the principles underlying separation on AgN03-impregnated adsorbents, the total number of double bonds per molecule can be assumed to be the same for all the lecithin molecules belonging to the same fraction. I t follows from this assumption and the GLC data quoted above that fraction A should largely be composed of only two kinds of lecithin molecules : palmitoy1 oleoyl glycerophosphoryl choline plus stearoyl oleoyl glycerophosphoryl choline, designated PC(16 :O, 18 : 1) and PC(18:0, 18: l), respectively. For logical reasons the possibility of appreciable quantities of molecules with other fatty acid combinations occurring in fraction A must be excluded. In the same way it can be deduced that fractions B, C, and D should also consist mainly of simple binary mixtures. Fraction B is PC(16:0, 18:2) plus PC(18:0, 18:2), fraction C is PC(16:0, 20:4) plus PC(18:0, 20:4), and fraction D is PC(16:0, 22:6) plus PC(18:0,22:6). The present report offers direct experimental support for this conclusion. I t describes the resolution of A, B, Cy and D into one palmitateand one stearate-containing subfraction by reversed-phase partition TLC.