516 



G, H. BEAVEN, E. R. HOLIDAY, AND E. A. JOHNSON 



210 



230 



250 



270 



290 



310 



Wavelength, rriM 



Fig. 16. Cytosine deoxyriboside (Fox and Shugari*). 



nucleic acid acquire an importance comparable with the viscosity and the 

 sedimentation constant in the assessment of the macromolecular status of 

 the nucleic acid. 



2. The Absorption Spectra of Nucleic Acids 



Because of their varying content of water the molar absorptivities of 

 nucleic acids cannot reliably be based on weight. A more practicable con- 

 vention has been suggested by Chargaff and Zamenhof." Since nucleic 

 acids contain one phosphorus atom per nitrogenous base, these workers 

 relate the absorbance of a solution of nucleic acid to phosphorus concen- 

 tration and derive a molar absorptivity, e(P), for nucleic acid, based on 

 one gram-atom of phosphorus per liter. 



" E. Chargaff and S. Zamenhof, J. Biol. Chem. 173, 327 (1948). 



