phospholipids in blood and tissues. 



Journal of Biological Chemistry , 142: 



659-670. 

 Acetone alone precipitated 40-70% of the 

 phospholipid from plasma and tissues when 

 0.3 to 2 mg. of phospholipid in 1 cc. of pe- 

 troleum ether and 7 cc . of acetone were 

 used. Complete precipitation was achieved 

 on addition of 1 drop of saturated or 0.1 cc . 

 of 30% MgCl,-6H20 in 95% ethanol. Addi- 

 tion of more MgCl2 caused incomplete pre- 

 cipitation. WhenMgCl2 was not used for 

 precipitation, all of the tissue phospholipid 

 and most of the plasma phospholipid precip- 

 itated were soluble in moist ether. The 

 percentage of ether -insoluble phospholipid 

 precipitate increased in proportion to the 

 amount of MgCl2 used, up to about 20% for 

 the tissue phospholipid, and 90% for the 

 plasma phospholipid. The ether -insoluble 

 portion was found to be a portion of the to- 

 tal phospholipid mixture, and not simply 

 the sphingomyelins. 



Sloot, W. J. T. A. K. 



1939-40. Determination of total fat con- 

 tent in small amounts of tissue. Acta 



^ Neerlandica morphologiae normalis et 



pathologicae , 3: 406. Chemical Ab- 

 stracts , 37:40l4 (1943). 

 Lipids are extracted from dried tissue 

 with absolute EtOH and the solvent is evap- 

 orated. The dry lipid is oxidized with 

 K2Cr207 and Ag reagent, KI is added, and 

 excess dichromate is titrated with Na2S203. 



Smits, G. 



1957. Modification of the periodide meth- 

 od for the determination of choline. 

 Biochimica et Biophysica Acta, 26: 424- 

 427. ~ 



The choline periodide precipitate is dis- 

 solved in ethylene dichloride which contains 

 a little iodine, and water is added. The ex- 

 tinction of the ethylene dichloride solution 

 of choline periodide is measured at 365 m u. 

 The interfering I'"' ions remain in the water 

 phase. 



Snyder, F . and N . Stephens 



1959. Simplified spectrophotometric de- 

 # termination of ester groups in lipids. 



Biochimica et Biophysica Acta, 34: 244- 

 245. 

 A simplification of the hydroxamic acid- 

 ferric perchlorate spectrophotometric meth- 

 od which is adapted for use with multiple 

 samples. The color can be developed in 20 

 to 30 samples in 15 to 20 minutes. Range 

 to 4.00 micro equivalents of ester. 



Sobel, A. E., I. J. Drekter, andS. Natelson 

 1936. Estimation of small amounts of 

 cholesterol as the pyridine cholesteryl 



■ sulfate . Journal of Biological Chemis- 

 try, 115 : 381-390. 



A method is described for determination 

 of free, esterified, and total cholesterol in 

 the same sample of blood serum . The free 

 cholesterol is isolated as pyridine choles- 

 teryl sulfate, and measured colorimetri- 

 cally by the Liebermann-Burchard reaction. 

 Esterified cholesterol is determined in the 

 same manner after hydrolysis of the cho- 

 lesterol esters. Recovery of 0.025 mg. of 

 added cholesterol was quantitative (+ 4%), 

 with better recovery when large amounts 

 were used. 



See also: Drekter, Journal of Biological 

 Chemistry , 115 : 391, 1936. 



Sobel, A . E . and A.M. Mayer 



1945. Improvements in Schoenheimer- 

 Sperry method for determination of 



■ free cholesterol. Journal of Biological 

 Chemistry, 157: 255-264. 



Extraction of the serum at room temper- 

 ature was found to be as good as the hot ex- 

 traction of S & S . Fifty percent alcoholic 

 digitonin gave a more workable precipitate 

 than the aqueous digitonin of S & S. Precip- 

 itation of cholesterol was found to be com- 

 plete in 3 hours at 37° . 



Sobel, A. E., J. Goodman, andM. Blau 

 1951 . Cholesterol in blood serum . 

 Studies of microestimation as the 



■ pyridinium cholesteryl sulfate . Ana - 

 lytical Chemistry, 23: 516-519. 



A method for determination of choles- 

 terol as the pyridinium cholesteryl sulfate 

 is described. Cholesterol is dissolved in 

 CCI4, and pyridine and chlorosulfonic acid 

 are added. The resulting precipitate 



64 



