SIDNEY SHlFIilN AND NATHAN O. KAPLAN 



149 



Recent studies by Sheinker et al. (19), using 2-mercaptothiazole, 

 which exists in the thione lorm, liavc demonstrated intermolecular 

 hychogen bonding from the amino to the thione group: 



N-H 



■— S 



IT 



N-H 



K^ 



An interesting reaction ol the thionicotinamide-DPNH was ob- 

 served upon expostae of a sohition of the reduced coenzyme analogue 

 to strong light. The 898 mfi maximinn is almost completely lost 

 under such conditions, and a new band appears with a maximum at 

 :M1 rUfi, as shown in Fig. 7. In addition, the absorption in the 295-300 

 mfx region is no longer present, a fact suggesting that the thione func- 



280 



320 



360 



400 



WAVELENGTH (m/x) 



440 



Fig. 5. Comparison of the .spectra of thioiiicolinainide Dl'NH in water and 

 propylene glycol. Solid line, alisorption spectrum of 9.0 X 10"^ M liiionicotina- 

 mideDPNH in water. Broken line, absorption spectrum of the same concentration 

 of the reduced analogue in propylene glycol. 



