486 



NIACIN 



final proof of the structure of an organic compound by chemical synthesis 

 has not yet been reported. Some progress in this direction has been made 

 since some portions of the molecule can now be synthesized. ^^ The lability 

 of various portions of the DPN molecule, especially the nicotinamide- 

 ribose bond, in the procedures ordinarily used in organic syntheses, makes 

 this a most difficult problem. 



6. Properties 



DPN is a white amorphous powder which is colorless in water solution. 

 It is moderately soluble in phenol and in methanol-HCl. Some of the 



TABLE VIII 

 Some Properties of DPN and TPN (from F. Schlenk^^") 



DPN 



TPN 



Empirical formula 

 structural units 



Base equivalent 



Oxidized state 



Reduced state 



Stability 



Oxidized state 



In 0.1 A^ HCl at 100° 

 In 0.1 N NaOH 

 Reduced state 

 In 0.1 A^ HCl at 20° 

 In 0.1 A^ NaOH at 100° 

 In 0.1 A^ NaOH at 20° 

 Absorption spectrum 

 Oxidized state 

 Reduced state 

 Reduced state 

 Oxidation-reduction poten- 

 tial 



C21H27O14N7P2 



Nicotinamide, adenine, 2 moles of 



ribose, and 2 moles of phosphoric 



acid 



50% destroyed after 8 min. 



50% destroyed after 17 min. (20°) 



Activity disappears immediately 

 Slight decrease in activity 

 Stable 



Em = 16.5 X 103 at 260 m^ 

 E,n = 14.5 X 10' at 260 m^i 

 Em = 4.5 to 6.3 X 103 at 340 m^i 

 En = -0.28 to 0.31 v 



CziHjsOnNTPi 



Nicotinamide, adenine, 2 moles of 

 ribose, and 3 moles of phosphoric 

 acid 



50% destroyed after 7.3 min. 

 50%, destroyed after 12 min. (23°) 



Activity disappears immediately 



Stable 



Em = 16.5 X 10' at 260 m^ 

 E,„ = 14.5 X 10' at 260 m^ 

 Em = 4.5 to 6.3 X 10' at 340 m^ 



important properties are listed in Table VIII. It is stable to oxidants such 

 as bromine, H2O2, and permanganate in acid solution unless catalysts such 

 as iron are present.^' ^"' ^^ Hypoiodide results in rapid destruction,^^ whereas 

 hyposulfite reduces DPN to DPNH2.'' Alkaline ferricyanide converts DPN 

 to a pyridone derivative. The latter can be condensed to yield a fluorescent 

 product, which reaction has been used as the basis for assay methods.^*"^* 



32a F. Schlenk, in The Enzymes, Vol. 2, Part 1, p. 263. Academic Press, New York 



1951. 

 33 P. Karrer, F. Schlenk, and H. von Euler, Arkiv Kemi, Mineral. Geol. 12B, 26 (1936) 

 3^ W. E. Knox and W. I. Grossman, /. Biol. Chem. 166, 391 (1946); 168, 363 (1947). 

 3i* F. Rosen, W. A. Perlzweig, and I. G. Leder, /. Biol. Chem. 179, 157 (1949). 

 36 K. J. Carpenter and E. Kodicek, Biochem. J. 46, 421 (1950). 



