506 



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



210 230 250 270 290 



Wavelength, rriM 

 Fig. 9. Thymine (Shugar and Fox'*). 



310 



Kalckar^^ was apparently unable to distinguish adenosine from adenine 

 even though using such an instrument. Schlenk and co-workers^' give an 

 absorption curve for xanthosine at pH 7.5, and curves for synthetic xantho- 

 sine are given by Todd and co-workers.*" Even allowing for unsuitable pH 

 values the latter are in poor agreement with the results of Schlenk and 

 those given here, and also with the much older values of Gulland et al.,*^ 

 all of which are reasonably consistent. 



The incompleteness of the data available for purine ribosides seemed 

 again to require a more systematic investigation, the results of which are 

 given in Figs. 11 to 14, and in Table II. For the pyrimidine nucleosides 

 recourse was had to Fox and Shugar'^ (Figs. 15 to 18), again by far the most 

 complete set of data, and for 5-methylcytosine deoxyriboside to Dekker 

 and Elmore.*- Absorbance ratios are from Cohn wherever available. Other 



" M. L. Schaedel, M. J. Waldvogel, and F. Schlenk, J. Biol. Chem. 171, 135 (1947). 

 " G. A. Howard, A. C. McLean, G. T. Newbold, F. S. Spring, and A. R. Todd, J. 



Chem. Soc. 1949, 232. 

 *' J. M. Gulland, E. R. Holiday, and T. F. Macrae, J. Chem. Soc. 1934, 1639. 

 « C. A. Dekker and D. T. Elmore, J. Chem. Soc. 1951, 2864. 



