Radiophosphorus and Nucleic Acids 



177 



Experiments along these lines by W. C. Hutchison and 

 S. C. Frazer have also been extended to an investigation of 

 the Schneider (1945) procedure in which the extracted tissue 

 powder is treated with hot 10 per cent trichloracetic acid 

 (TCA) to remove nucleic acids as acid soluble fragments on 

 which pentose and deoxypentose are estimated. It might be 

 supposed that nucleic acid phosphorus would be removed in 

 the hot acid extract, leaving "phosphoprotein" phosphorus 

 in the insoluble residue, but Table III shows that the residue 

 contains much more phosphorus than would be expected 

 and that its activity, due in part to highly active "phospho- 

 protein," is much greater than that of the phosphorus in the 



Table III 



Concentrations and Activities of Phosphorus Fractions Obtained 



FROM HoMOGENATES OF RaBBIT LiVER BY THE SCHMIDT AND ThANNHAUSEB 



Procedure and by the Schneider Procedure 

 10 fxc. ^^P per 100 g. body weight were injected two hours before killing. 



acid extract which is derived from the mixed RNA and DNA. 

 When the Schneider residue is submitted to a Schmidt- 

 Thannhauser separation, the inorganic phosphate released on 

 alkaline incubation corresponds both in amount and in 

 activity to the "phosphoprotein" phosphorus found by the 

 original Schmidt-Thannhauser method, but it is accompanied 

 by phosphate esters of surprisingly high activity (Table IV). 

 To examine the possibility that the highly active "phos- 

 phoprotein" phosphorus found by the Schmidt-Thannhauser 

 procedure might consist mainly of inorganic phosphorus 

 which had failed to be removed in the preliminary extraction 

 of the tissue with TCA, Hutchison and Frazer compared the 

 effects of extracting fresh liver homogenates 3, 6 and 20 



ISOTOPES 



13 



