OPTICAL PROPERTIES OF NUCLEIC ACIDS 



517 



210 



230 



270 



290 



250 



Wavelength, rriM 

 Fig. 17. Thymidine (Fox and Shugar'^). 



As defined by Chargaff and Zamenhof 



6(P) = AlC-d 



A and d have been defined above; C is measured in gram-atoms of phos- 

 phorus per Uter. 



A review of pubUshed values of e(P) shows very wide variation, from 

 G,000 to 8,000 for DXA, and from 7,000 to 10,000 for PNA. When results 

 have not been expressed in accordance with this convention, comparison 

 with other work is often impossible. The €(P) value of a nucleic acid meas- 

 ured under standard conditions may eventually serve as an index of the 

 degree of denaturation. 



Two general conclusions may be stated: 



(a) All recorded values of €(P) for intact DNA and PNA are lower than 



