13G WALTER JOXES 



acid). (Kossel and Xeuman (a)(b)(c), 1893, 1894.) It will, therefore, 

 he necessary and sufficient to examine two nucleic acids in o,dcr to get a 

 knowledge of them all. 



The Fundamental Groups of Yeast Nucleic Acid. When yeast nu- 

 cleic acid is heated for a short time with very dilute sulphuric acid, part 

 of its molecule easily undergoes hydrolysis with the formation of pentose, 

 phosphoric acid and two purine derivatives (guanine and adenine). But 

 when the nucleic acid is suhmitted to severe hydrolysis hy heating with 

 stronger sulphuric acid in an autoclave at 160, a second part of its mole- 

 cule is decomposed with the formation of peutose and phosphoric acid 

 as hefore, but in addition, two pyrimidine derivatives (cystosine and 

 uracil). So that by hydrolysis with mineral acid in one way or another, 

 yeast nucleic acid produces six substances. / 



1. Phosphoric Acid 



2. Pentose 



3. Adenine 



4. Guanine 



5. Cyiosine 



6. Urac-ll 



These six substances constitute the fundamental groups of which yeast 

 nucleic acid is composed, and as will be seen later, the same six substances 

 are formed when yeast nucleic acid is decomposed by physiological agents. 

 One of them is so simple as to require no treatment ; the other five should 

 be discussed. 



Pentose. There are theoretically possible, eight aldo-pentoses of the 

 formula C 5 H 10 O 5 . The substance which is obtained from yeast nucleic 

 acid is that one of the eight possibilities that has the geometrical config- 

 uration called dextro-ribose. (Levene and Jacobs (c) (g) (/i), 1909, 1909, 

 1910.) 



CHO 



ECOH 

 HCOH 

 HCOH 

 CILOH 



This configuration is unique, being found very rarely in nature, and it 

 probably has great physiological significance, but at present we can only 

 refer d-ribose to the general metabolism of the carbohydrates; in which 

 case it does not properly fall into a discussion of nucleic acids. 



The Pyrimidine Derivatives. Both cytosine (Kossel and N"euman (a) 

 (&), 1893, 1894), (Kossel and Stendel (a) (6), 190i>, 1903) and uracil 



