IV. BIOCHEMICAL SYSTEMS 



487 



Treatment with bisulfite and cyanide give addition compounds" while 

 strong acids give pyridinium salts. 



DPN is sensitive to ultraviolet light, being destroyed thereby.^^"^" DPN 

 shows no fluorescence in ultraviolet light, but DPNH2 exhibits a whitish 

 fluorescence. DPN is optically active, the specific rotation being —20° at 

 643.9 mix and -70° at 546 m/x.'^ 



DPN shows an absorption peak at 260 van hi the ultraviolet. DPNHj 



10^ cm.2/g. DPN 

 60 



50 



40 



30 



20 



10 



260 



300 



340 



380 



Mm 



Fig. 7. Ultraviolet absorption spectrum of diphosphopyridine nucleotide (pH 

 9.7); oxidized (O) and reduced (•) forms. (Adapted from Warburg and Christian.^) 



also exhibits a peak at 260 m/z and, in addition, a peak at 340 m^ which 

 is entirely absent in the oxidized form (Fig. 7). This band at 340 m/i has 

 been the basis for innumerable assay methods and has major biochemical 

 usefulness. 



" O. Meyerhof, P. Ohlmeyer, and W. Mohle, Biochem. Z. 297, 113 (1938). 

 38 O. Warburg and W. Christian, Biochem. Z. 282, 221 (1935). 

 " J. Runnstrom and L. Michaelis, /. Gen. Physiol. 18, 717 (1935). 

 "0 H. von Euler and F. Schlenk, Arkiv Kemi, Mineral. Geol. 12B, 19 (1936). 

 *^ K. Myrback, H. von Euler, and H. Hellstrom, Hoppe-Seyler's Z. physiol. Cheni. 

 212, 7 (1932). 



