400 R. M. S. SMELLIE 



tissue at different time intervals, and that the renewal of the two nucleic 

 acids proceeds at different rates in the different tissues. 



c. The Uptake of P^^ by the Individual Nucleotides Derived from the PNA of 

 Different Tissues 



Since the phosphorus of PNA is distributed among its four constituent 

 nucleotides, it is desirable to study the renewal of phosphorus in each 

 nucleotide separately. 



Several methods for the separation of mononucleotides by paper chro- 

 matography (Chapter 7) have been described."' ''* None of these is suitable 

 for measurements of radioactivity of the individual nucleotides since in 

 every instance one pair of nucleotides is not completely resolved. Volkin 

 and Carter"* have separated the mononucleotides derived from PNA and 

 DNA by the ion-exchange technique of Cohn"^ (Chapter 6) and have meas- 

 ured the incorporation of radioactive phosphorus into the nucleotides of 

 PNA and DNA from several samples of liver tissue. Davidson et a/.^'^^'^""""^ 

 have applied their ionophoretic technique"^ to the separation of the ribose 

 mononucleotides present in alkaline hydrolysates of PNA extracted from 

 several different liver tissues and tissue fractions. Boulanger et al.^°-^^ have 

 made use of a chromatographic method in their studies on the kinetics of 

 P32 incorporation into the PNA of whole rat liver tissue. 



From the results of these workers, it appears that in general the specific 

 activities of the four ribose mononucleotides are similar to one another, 

 adenylic acid usually exhibiting the highest activity and guanylic acid 

 the lowest, while the activities of the pyrimidine nucleotides give inter- 

 mediate values. It may be of significance that the activities of the four 

 nucleotides are approximately in inverse proportion to their relative molar 

 proportions within the PNA. 



d. The Effect of Physiological and Pathological Changes on the Metabolic 

 Activity of PNA 



We have seen already that the uptake of P'^ by DNA in regenerating 

 liver and in hepatoma is considerably raised as compared with the normal. 



*^ B. Magasanik, E, Vischer, R. Doniger, D. Elson, and E. Chargaff, J. Biol. Chem. 



186, 37 (1950). 

 " C. E. Carter, J. Am. Chem. Soc. 72, 1466 (1950). 

 « R. Markham and J. D. Smith, Biochem. J. 49, 401 (1951). 

 « E. Volkin and C. E. Carter. J. Am. Chem. Soc. 73, 1519 (1951). 

 " W. E. Cohn, J. Am. Chem. Soc. 72, 1471 (1950). 

 « J. N. Davidson, Bull. soc. chim. biol. 35, 49 (1953). 

 49 J. N. Davidson and R. M. S. Smellie, Biochem. J. 52, 594 (1952). 

 ^" P. Boulanger, J. Montreuil, and L. Masse, Compt. rend. 234, 565 (1952). 

 " P. Boulanger and J. Montreuil, Biochim. et Biophys. Acta 9, 619 (1952). 



