Peat of Certain Nucleic Acid Derivatives. 



43 



the precipitation of the guanine by ammonia was examined by the method of 

 Jones, already described, for pyrimidiues, and cytosine was obtained. 



A simpler method for the isolation of this base was found in the use of 

 mercuric sulphate, which dispenses with the need of a silver salt. Tbe bulk 

 of the filtrate was therefore acidified with sulphuric acid and a solution of 

 mercuric sulphate added. After standing for 24 hours the precipitate was 

 removed by filtration, decomposed with hydrogen sulphide, and the filtrate 

 from the mercuric sulphide concentrated. From this the following salts of 

 cytosine were obtained : an almost insoluble pierate in the form of needles ; 

 a chloroplatinate, as six-sided plates ; a chloride, as needle crystals. The free 

 base was obtained in the form of pearly plates by precipitating with ammonia, 

 and this gave the colour reaction of Wheeler and Johnson. By these reactions 

 the substance was identified as cytosine. 



Thus the filtrate contains the four radicles of another dinucleotide — 

 phosphoric acid, sugar, guanine and cytosine — a guanine-cytosine dinucleotide. 



Various kinds of peat from different localities and varying depths have been 

 extracted, and all have given similar results. 



Conclusions. 



It is evident from the above results that all the constituents of a true 

 nucleic acid are present in raw peat, but nucleic acid as such has not been 

 isolated. Nucleic acid must have been present in the plants from which peat 

 has been formed, and since it is improbable that hydrolysis could have been 

 brought about by the methods of extraction employed, the original nucleic 

 acid has evidently been decomposed by bacterial or other agencies during the 

 process of peat formation, into the products which have been isolated. 



It is generally assumed that the first step in the decomposition of nucleic 

 acid results in the formation of four mononucleotides. Levene and 

 Medigreceanu* state that the first phase in the enzymatic decomposition of 

 yeast nucleic acid is the formation of four mononucleotides by the action of a 

 ferment called " nucleinase." It is evident, however, that the decomposition 

 of peat nucleic acid in situ has not followed these hues, but has yielded a 

 stable adenine-uracil dinucleotide and the component parts of a guanine- 

 cytosine dinucleotide. 



This is interesting in view of the recent work of Jones and Grermann,f who 

 have shown that when yeast nucleic acid is submitted to alkaline hydrolysis 

 it is split up into two very definite dinucleotides : a guanine-cytosine 

 dinucleotide and an adenine-uracil dinucleotide. They state that the former 



* Levene and Medigreceanu, ' Journ. Biol. Chem.,' vol. 9, p. 65 (1911). 

 t Jones and Germann, ' .Journ. Biol. Chem.,' vol. 25, pp. 98 et seq. (1916). 

 VOL. XC. — B. F 



