EFFECT OF X-RAYS ON NUCLEIC ACID IN JENSEN-SARCOMA 697 



6 are obtained by dividing by the colorimetrically determined weight 

 of the phosphorus in the nucleic acid. 



The Sarcomas Used 



Jensen sarcomas of rats, which had been cultivated by transphmting 

 a sarcoma obtained from Professor Domagk were used for all the 

 experiments which we have described up to this point. 



The sarcomas were always transplanted subcutancously by installing 

 a tissue section about 1 mm thick. The sarcomas developed in our strain 

 of rats up to a size of about 20 gm in about 3 weeks. Rats with a sarcoma 

 weight of about 20 — 30 gm were ordinarily used in the irradiation experi- 

 ments. 



Isolation of the Nucleic Acid 



The sarcoma tissue was finely minced and worked up for desoxyribo 

 nucleic acid by the method described by Klein and Beck^^\ The crude 

 precipitate was dissolved in 1 N caustic soda, treated with about 80 mgm 

 of disoclium hydrogen phosphate and precipitated with 5% ferric hydro- 

 xide solution. This purification of the nucleic acid was repeated two more 

 times to remove any radioactive phosphate. The product obtained in 

 this way was then twice dissolved and reprecipitated, with methyl 

 alcohol containing hydrochloric acid, in accordance with the method 

 of Klein and Beck. The most careful purification of the nucleic acid 

 from foreign phosphates is of the utmost importance because the acid- 

 soluble phosphate is much more active than the phosphate from the 

 nucleic acid. 



The phosphate in the finally purified precipitate was determined 

 colorimetrically by the method of Fiske and Subbarow^^^ (Theorell's 

 modification^^^) . Another portion was precipitated as magnesium ammo- 

 nium phosphate which was then used for determining the activity. 



With regard to the quantities employed in this procedure, the reader 

 is referred to the description supplied as an example (p. 692) and also 

 to Tables 1 — 6 (pp. 699 — 702). 



The samples of blood and liver were worked up by the methods describ- 

 ed below: 



The blood, which had been collected in a vessel containing a few 

 milligrams of sodium citrate, was centrifuged; the plasma (usually 

 2—3 cm^) was treated with 3 cm-"^ of 10% trichloroacetic acid, the 



10. Klein and Beck, Z. Krehsforsch. 42, 163 (1935). 

 2 Fiske and Subbabow, J. Biol. Chem. 66, 375 (1925). 

 ^Theorell, Biochem. Z. 230, 1 (1931). 



