152 



LIGHT AND LIFE 



280 



320 



360 



400 



440 



WAVELENGTH (m/x) 

 Fig. 8. Spectrum of the niethylated product of thionicotinamide analogue of 

 DPNH. S-DPNH, 9.0 X 10'' M tliionicotinaniide-DPNH in 0.1 M sodium bicar- 

 bonate buffer, pH 9.0. MeS-DPNH, 9.0 x 10"^ M thionicotinamide-DPNH treated 

 with 2 X 1'*"' ^^ dimethyl sulfate at room temperature in 0.1 M sodium bicar- 

 bonate buffer. The absorption spectrum was taken one hour after the reactants 

 were mixed. Precautions were taken to prevent exposure of the reduced analogue 

 to light during this period. 



TABLE 2 

 Absorption Spectra of Thiol Pyridine Derivatives 



Compound 



(mfx) 



10-»e 



S-DPNH 



S-DPNH (M® 

 Pyrid-2-thione 

 2-Benzylthiopyridine 



398 

 342 

 340 

 290 



8.9 

 4.4 

 8.7 

 5.5 



9.0 aiul at room temperature, the spectral changes shown in Fig. 8 

 are obtained. While adenine has been shown to react with dimethyl 

 sulfate (7) , the portion oi the spectrum which is examined represents 

 absorjHion by the dihydrothioni(otinamide moiety. The reaction of 

 mciliyl sulfate with the reduced thionicotinamide may be represented 

 by the following equation: 



