18() 



RADIATIOX BIOLOGY 



conipoiiciit iiuclcotidos hut are appnM-iably les.s, siig}z;(\stinjj; wcjik iutcr- 

 mitl(>i)litl(' liiikjit?(>s, alT(>ctiiiK the absorhing .structuros (Fi^j;. .'»-l(i). 



The spectra of the iiuli\ idiial miclcot ides are easily disliuKuished (Kig. 

 5-17); they are generally similar to the spectra of the component purine 

 and pyrimidiiic hases, which hases are primarily responsible for the 

 absorption of these compounds in the spectral region above 2300 A. The 



200 



240 



320 



280 

 WAVE LENGTH, rr\ p. 



Fig. 5-15. Absorption spectrum of trypsin in acid and in alkaline sohition, and of the 



trypsin-trypsin inhibitor complex (e = :3fi,700 K). • •, trypsin in .V/lOO 



H2SO4; O O, trypsin in A/10 HCl; ® ®, trypsin after 24 hours in A710 HCl; 



3 9, heat-inactivated trypsin; O O, trypsin in A/10 NaOH; O O, 



trypsin inhibitor complex. (Schonnuller, 1949.) 



spectra are sensitive to changes in pH, especnally in the regions of the pK 

 vahies of the functional groups attached to the purines and pyrimidines 

 (Stimson, 1949) . Absorption in these bases is considered to be dependent 

 on the presence of — C^C— C=N— or — C=C— C=0 groupings 

 (Cavalieri and Bendich, 1950). 



STEROIDS 



Although all steroids will exhibit end absorption in the region below 

 2100 A, only those steroids that contain sequences of conjugated double 



