538 NIACIN 



down of the coenzymes. The reduced coenzymes are oxidized, after which 

 the same procedure is used as for determining coenzymes in blood. 



Kaplan et al.^^ have recently proposed a chemical method based on the 

 facts that oxidized DPN and TPN are split by alkali and that treatment 

 with strong alkali produces a bluish fluorescence which can be quantitated. 

 When crude tissue extracts were used, the difference in fluorescence before 

 and after the coenzymes were destroyed with an enzyme (DPNase from 

 Neurospora) w^as a measure of the amount of DPN-TPN originally present. 

 N^-Methylnicotinamide interfered slightly in the test. The method has not 

 yet received its baptism of fire by being tried in tissue studies by other 

 investigators. 



7. Other Methods 



Feinstein^^ has devised a rapid, simple test to determine whether flour 

 has been enriched with nicotinic acid. A few drops of aniline are dropped 

 into the center of a packed sample of the flour. A few drops of cyanogen 

 bromide are dropped on top of the spot wet from the aniline. A canary 

 yellow color appears promptly, and the depth of the color is roughly pro- 

 portional to the amount of nicotinic acid in the flour. 



C. MICROBIOLOGICAL METHODS 



E. E. SNELL 



Nicotinic acid and nicotinamide have been found essential for a great 

 variety of bacteria and yeasts since the nutritive importance of these com- 

 pounds for bacteria was first indicated by the work of Lwoff and Lwoff 

 with influenza bacilli,'*'' of Knight with staphylococci,^^ of Mueller with 

 diphtheria organisms,^^ and of Snell and coworkers with lactic acid bac- 

 teria."*^ 



A number of nicotinic acid derivatives occur naturally (e.g., nicotina- 

 mide, coenzymes I and II, N^-methylnicotinamide, trigonelline, quinolinic 

 acid, etc.), and selection of an assay organism for which the activity of 

 these compounds parallels their activity for animals is important. Nico- 

 tinic acid and nicotinamide have widely different activities for staphylo- 

 cocci, corynebacteria, dysentery organisms, pasteurella, and several other 

 bacteria, and hence these organisms are not entirely satisfactory for assay 



38 N. 0. Kaplan, S. P. Colowick, and C. C. Barnes, J. Biol. Chem. 191, 461 (1951). 



39 L. Feinstein, Science 101, 675 (1945). 



" A. Lwoff and M. Lwoff, Proc. Rorj. Soc. (London) B122, 352 (1937). 

 « B. C. J. G. Knight, Biochem. J. 31, 731, 966 (1937). 

 « J. H. Mueller, J. Biol. Chem. 120, 219 (1937). 



« E. E. Snell, F. M. Strong, and W. H. Peterson, J. Am. Chem. Soc. 60, 2825 (1938); 

 /. Bacterial. 38, 293 (1939). 



