THE SPHINGOMYELINS 450 



Thannluiuser and Bcnotti'''-^ have recently prepared glycerol-free sphingo- 

 myelin from Imig tissue, but this has not been achieved in the case of brain 

 sphingomyelin, where the large proportion of cerebrosides and of saturated 

 monophosphatides causes considerable interference. Klenk and Renn- 

 kamp'2^ succeeded in accomplishing this purification by subjection of the 

 crude sphingomyoliii to sapoiiificatiou with so(Hum alcoholato, which had a 

 more or less sclecti\'e action in producing hydrolysis of the monophospha- 

 tides. Thannhauser and Benotti^-^ found that saponification at a boiling 

 temperature was too drastic a procedure; they accomplished the purifica- 

 tion by shaking the impure sphingomyelin preparation with aqueous sodium 

 hydroxide at 37°C. for 24 hours. 



(4) Properties of the Sphingomyelins 



Sphingomyelins are white crystalline substances which are not hydro- 

 scopic, in contradistinction to the behavior of their most important compo- 

 nent, sphingosine. These phosphatides are resistant to air and light. They 

 are only slightly soluble in cold alcohol or pyridine, and can be crystallized 

 from these solvents when hot solutions are cooled. Thus, 100 ml. of a satu- 

 rated pyridine solution of sphingomA^elin contains 0.22 g. of the solute at 

 40°C. and 0.18 g. at room temperature. Sphingomyelins are almost com- 

 pletely insoluble in acetone and diethyl ether, but they form emulsions ^vith 

 water which exhibit mj'elin formation. In an aqueous solution of glycerol, 

 they exhibit birefringence. ^^^ Sphingomyelin melts at 196-198°C.^^® 



Like lecithin, sphingomyelin forms a cadmium chloride compound which 

 is difl&cultl}^ soluble in alcohol. It also combines w^th platinum to give a 

 salt sparingly soluble in alcohol, as well as in diethyl ether. -^^ The phospho- 

 lipid also exhibits optical activity. In a methyl alcohol-chloroform solu- 

 tion, a dextro-rotation is observed. Levene*" reported specific rotations for 

 different preparations varying from 7.53° to 8.73°, while Walz^" gave a 

 value for [a]^ of -f5.5°. In pyridine, the optical rotation is strongly dex- 

 tro-rotatory above 40° ([a]^ = H- 13.82°). However, when the solution is 

 cooled, the optical activity changes from a dextro- to a levo-rotation.^^® 



It is believed that sphingomyelin may occur in the z\vitterion form. 

 Although Chain and Kemp^-^ found that the isoelectric point of this phos- 

 phatide as determined electrophoretically was approximately at a pH of 6.0, 

 Fischgold and Chain^* observed that, in a benzene alcohol solution, sphingo- 

 myelin bound one equivalent of hydrogen ions, but did not yield hydrogen 



"* S. J. Thannhauser and J. Benotti, Unpublished experiments, reported by S. J. 

 Thannhauser and G. Schmidt, Physiol. Revs., 26, 286, 287 (1946). 



'** R. Kawamura, Die Cholesterinesterverfettung, Fischer, Jena, 1911, p. 9. 



'2« M. Sano, /. Biochem. Japan, 1, 1-16, 17-20 (1922). 



32T E. Walz, Z. physiol. Chem., 166, 22.3-226 (1927). 



«« E. Chain and I. Kemp, Biochem. J., SS, 2052-2055 (1934). 



