OPTICAL PROPERTIES OF NUCLEIC ACIDS 



515 



220 



240 



280 



260 



Wavelength, rriM 

 Fig. 15. Cytidine (Fox and Shugar'*). 



300 



ultraviolet absorption characteristics of nucleic acids is not possible at the 

 moment. The recent spectrophotometric studies by Cavalieri,^^ Shack 

 et a?.,^^'^^ Thomas, ^^ and Lawley (working in Jordan's laboratory),*^ indicate 

 that hitherto unsuspected factors may cause irreversible changes in the 

 absorption spectrum of DNA. These changes in the macromolecular struc- 

 ture we may term, from protein analogies, denaturation. Consequently, 

 many preparations and physical studies of DNA have been carried out 

 under conditions which have since been found to cause denaturation. In 

 the light of these findings the ultraviolet absorption characteristics of a 



" L. F. Cavalieri, J. Am. Chem. Soc. 74, 1244 (1952). 



" J. Shack, R. J. Jenkins, and J. M. Thompsett, /. Biol. Chem. 198, 85 (1952). 



" J. Shack, R. J. Jenkins, and J. M. Thompsett, J. Biol. Chem. 203, 373 (1953). 



" R. Thomas, Bull. soc. chim. biol. 35, 609 (1953). 



" P. D. Lawley, Ph.D. Thesis, Nottingham University, 1953. 



