56 CHOLINE 



sorbed choline is then ehited from the eohimn with 5 % sodium chloride. 

 Aliquots of the solution and of standard choline solutions are added to 

 flasks containing the basal medium, and these are inoculated and incubated 

 for about 3 days at 25°. The response of the mold to the added supplements 

 is determined by weighing the dried mycelium. SiegeP^ has recommended 

 the removal of the mycelium from the culture fluid by filtration through 

 a tared, sintered glass filter of medium porosity which is then dried and 

 weighed. Dry weights from duplicate flasks agree within about 5 %, and 

 choline values determined on different amounts of the same solution agree 

 within 10 %. Standard curves must be run with each assay. 



Luecke and Pearson^^ have used the method for the determination of 

 free choline in plasma and urine and for the estimation of free choline in 

 animal tissues. Comparative determinations on the same samples showed 

 that the microbiological values were in excellent agreement with those 

 obtained by chemical methods. Hodson^^ used a modification of the above 

 procedure in the assay of milk products. The results obtained with the 

 Neurospora procedure indicate that this method is considerably more sensi- 

 tive and more specific than the chemical methods investigated to date.^^ 

 The various analogs that support growth of the organism do not appear in 

 appreciable quantities in most biological materials or, as in the case of 

 methionine, can be separated by use of adsorbents. 



Special attention has been given the determination of choline-containing 

 phospholipids in blood, liver, and other tissues by workers in the labora- 

 tories of Thannhauser,37-39 Chaikoff,^''-''^ Chargaff,^^' "* and McKibbin.^^' '^ 



'3 L. Siegel, Science 101, 674 (1945). 



" R. W. Luecke and P. B. Pearson, J. Biol. Chem. 153, 259 (1944); 155, 507 (1944). 



35 A. Z. Hodson, J. Biol. Chem. 157, 383 (1945). 



3« F. J. Bandelin, /. Am. Pharm. Assoc. 38, 304 (1949). 



" G. Schmidt, L. Hecht, P. Fallot, L. Greenbaum, and S. J. Thannhauser, /. Biol. 



Chem. 197, 601 (1952). 

 38 S. J. Thannhauser, J. Benotti, and H. Reinstein, J. Biol. Chem. 129, 709 (1939). 

 3s S. J. Thannhauser, J. Benotti, A. Walcott, and H. Reinstein, J. Biol. Chem.. 129, 



717, (1939). 

 " C. Entenman, A. Taurog, and I. L. Chaikoff, J. Biol. Chem. 155, 13 (1944). 

 ^1 A. Taurog, C. Entenman, B. A. Fries, and I. L. Chaikoff, /. Biol. Chem. 155, 19 



(1944). 

 « C. Entenman and I. L. Chaikoff, J. Biol. Chem. 160, 377 (1945). 



43 E. Chargaff, M. Ziff, and D. Rittenberg, J. Biol. Chem. 138, 439 (1941); 144, 343 

 (1942). 



44 E. Chargaff, C. Levine, and C. Green, /. Biol. Chem. 175, 67 (1948). 



45 J. M. McKibbin and W. E. Taylor, /. Biol. Chem. 178, 17, 29 (1949). 



46 W. E. Taylor and J. M. McKibbin, J. Biol. Chem. 188, 677 (1951). 



