504 



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



210 



230 



250 



270 



290 



Wavelength, rriM 

 Fig. 7. Cytosine (Shugar and Fox'*). 



as thymine, and to a much greater extent in subhmed films than in glasses. 

 Changes with aging of sublimed films are observed which suggest that these 

 are initially largely amorphous but slowly become crystalline, a process 

 accelerated by the presence of water vapor. 



2. Nucleosides 



Since ribosides may be obtained by hydrolysis of PNA with much greater 

 ease than the deoxy- derivatives from DNA, the greater part of the avail- 

 able spectroscopic data refers to the former. A good series of absorption 

 curves for deoxyribosides has been published by MacNutt,^^ who examined 

 these derivatives of guanine, hypoxanthine, thymine, cytosine, and uracil. 

 Manson and Lampen^^ give absorption curves for the deoxyribosides of 



36 W. S. MacNutt, Biochem. J. 50, 384 (1952). 



3« L. A. Manson and J. O. Lampen, J. Biol. Chem. 191, 87 (1951). 



