On Nucleic Acids. 



93 



4. Finally, thymonucleic acid is a dipurin-dipyrimidin-gluco- 

 phosphoric acid. 



Conclusions as to the nature and existence of the monopurin- 

 glucophosphoric acid have passed through several phases during 

 the past year. Last summer a paper by v. Ftirth and Jerusalem 

 appeared in which the existence of the substance was denied. 

 However, within a short time, work done by Steudel, by Jones and 

 by ourselves has not only established the existence of the sub- 

 stance, but also has shown that its occurrence is more general in 

 animal organs than has hitherto been conceded. In fact, with the 

 acceptance of this discovery, some investigators are inclined to re- 

 gard thymonucleic acid as simply a mixture of different monopurin- 

 glucophosphoric acids. 



This view is not supported by our experiments. Both the car- 

 bohydrate and the purin bases are easily obtained on decomposi- 

 tion of guanylic acid, while great difficulty is experienced in ob- 

 taining these substances quantitatively, by hydrolysis of thymo- 

 nucleic acids. 



However, it is possible that all nucleic acids resemble one 

 another in the order in which the components are linked together. 

 There is support for the assumption that the carbohydrate is joined 

 to the phosphoric acid and the base to the carbohydrate in a 

 glucoside form. Thus, upon hydrolysis of inosinic acid by means 

 of alkali, a condition may be obtained in which the original solu- 

 tion is not changed in its rotatory power and does not show 

 reducing action on Fehling's solution, but which gives evidence of 

 the presence of free phosphoric acid. On the other hand various 

 workers report experiments in which on hydrolysis of inosinic acid, 

 a glucophosphoric acid was obtained which had the power of re- 

 ducing Fehling's solution and which formed phenylosazone. 



Furthermore on partial hydrolysis of thymonucleic acids, sub- 

 stances are obtained which contain only purins or only pyrimidins 

 linked to a carbohydrate. These substances have no reducing 

 power, but on further cleavage yield levulinic acid. 



These considerations, and also the results of our analysis of 

 the bases lead us to believe that the accepted view of the elemen- 

 tary composition and of the structure of the thymonucleic acids has 

 not yet been fully demonstrated. 



