182 



Elementary Chemical Ayialysis}— 

 Four purified preparations were ana- 

 lyzed for content of nitrogen, phos- 

 phorus, carbon, and hydrogen. The 



AVERY, MACLEOD, MCCARTY 



results are presented in Table I. The 

 nitrogen-phosphorus ratios vary from 

 1.58 to 1.75 with an average value of 

 1.67 which is in close agreement with 



Table I 



Elementary Chemical Ajialysis of Purified Preparations of the Transforming Substance 



that calculated on the basis of the 

 theoretical structure of sodium de- 

 soxyribonucleate (tetranucleotide) . 

 The analytical figures by themselves 

 do not establish that the substance iso- 

 lated is a pure chemical entity. How- 

 ever, on the basis of the nitrogen-phos- 

 phorus ratio, it would appear that little 

 protein or other substances containing 

 nitrogen or phosphorus are present as 

 impurities since if they were this ratio 

 would be considerably altered. 



Eyizymatic Analysis.— V Ninons crude 

 and crystalline enzymes ^ have been 

 tested for their capacity to destroy 

 the biological activity of potent bac- 

 terial extracts. Extracts buffered at the 

 optimal pH, to which were added 

 crystalline trypsin and chymotrypsin 

 or combinations of both, suffered no 

 loss in activity following treatment 

 with these enzymes. Pepsin could not 

 be tested because extracts are rapidly 



1 The elementary chemical analyses were 

 made by Dr. A. Elek of The Rockefeller 

 Institute. 



2 The authors are indebted to Dr. John H. 

 Northrop and Dr. M. Kunitz of The Rocke- 

 feller Institute for Medical Research, Prince- 

 ton, N. J., for the samples of crystalline 

 trypsin, chymotrypsin, and ribonuclease used 

 in this work. 



inactivated at the low pH required for 

 its use. Prolonged treatment with crys- 

 stalline ribonuclease under optimal 

 conditions caused no demonstrable de- 

 crease in transforming activity. The 

 fact that trypsin, chymotrypsin, and 

 ribonuclease had no effect on the trans- 

 forming principle is further evidence 

 that this substance is not ribonucleic 

 acid or a protein susceptible to the 

 action of tryptic enzymes. 



In addition to the crystalline en- 

 zymes, sera and preparations of en- 

 zymes obtained from the organs of 

 various animals were tested to deter- 

 mine their effect on transforming ac- 

 tivity. Certain of these were found to 

 be capable of completely destroying 

 biological activity. The various en- 

 zyme preparations tested included 

 highly active phosphatases obtained 

 from rabbit bone by the method of 

 Aiartland and Robison (15) and from 

 swine kidney as described by H. and 

 E. Albers (16). In addition, a prepara- 

 tion made from the intestinal mucosa 

 of dogs by Levene and Dillon (17) and 

 containing a polynucleotidase for thy- 

 mus nucleic acid was used. Pneumo- 

 coccal autolysates and a commercial 

 preparation of pancreatin were also 



