440 V. CHEMISTRY OF PHOSPHATIDES AND CEREBROSIDES 



identical except for the fact that the phosphorylethanolamine was com- 

 bined with the a- or the /3-carbon of glycerol. By dissolving a cephalin 

 complex from brain in chloroform and gradually precipitating with increas- 

 ing concentrations of alcohol, Folch"^" was able to obtain 5 fractions, 3 of 

 which were relatively pure, while the intermediate 2 (II and IV) appeared to 

 be mixtmes. Fraction I, which contained inositol phosphatide, was least 

 soluble in alcohol. Fraction III consisted largely of phosphatidylserine, 

 while fraction V consisted almost entirely of phosphatidylethanolamine. 

 Folch's data are summarized in Table 7. 



Table 7 

 Analysis of Fractions Isolated from Brain Cephalin by the Chloroform- 

 Alcohol Method" 



Fraction I, inositol phosphatide 

 Fractions II and IV, mixtures 

 Fraction III, phosphatidyl serine 

 Fraction V, phosphatidyl ethanolamine 



<- J. Folch, J. Biol. Chem., 146, 35-44 (1942). 



* By nitrous acid manometric method of D. D. Van Sljdve, /. Biol. Chem., 83, 449-461 

 (1929). 



' By ninh.ydrin-C(>, method of D. D. Van Slyke, R. T. Dillon, D. A. MacFadyen, and 

 P. Hamilton, J. Biol. Chem., I4I, 627-669 (1941). 



<^ In grams per 100 g. cephalin. 



It would thus appear that cephalin as formerly referred to in the litera- 

 ture is a mixture containing at least three types of molecules, instead of only 

 phosphatidylethanolamine. The general facts about cephalin as gleaned 

 from the early work in this field will be included under the section on phos- 

 phatidylethanolamine, with the full realization that much of the data may 

 refer to preparations which are quite impure and which may, in fact, be mix- 

 tures of the several types of cephalins. 



(^) Phosphatidyletltanolamiiie and CepJialins in General 



a. Structure of Phosphatidylethanolamine. The presence of a second 

 phosphatide in the brain, in addition to lecithin, which had a N:P ratio 



