NUCLEIC ACIDS. 181 



The simple nucleic acids are ester-like combinations between phosphoric 

 acid and a purine base-pentoside. 



The complex nuclei acids are complex molecules each composed of 

 four simple nucleic acids (nucleotides) . In regard to the complex nucleic 

 acids we differentiate between two groups. 



The acids of the thymonucleic acid group are, according to STEUDEL, 

 tetrabasic phosphoric acid ester which corresponding to each phosphorus 

 atom, contains a hexose group and one of the four bases, guanine, 

 adenine, cystosine and thymine. From the name of this group we infer 

 that these acids contain thymine. 



The plant nucleic acid group differs from the preceding by the follow- 

 ing. They do not contain any thymine but uracil instead. They do not 

 contain any hexose but do contain pentose. In the acids of this group 

 for each atom of phosphor we have 1 mol. pentose and on each the 

 purine and pyrimidine bases are combined. 



It must be remarked that the complex nucleic acids have not been 

 prepared from isolated component proteins but generally from organs, 

 namely perhaps from a mixture of different nucleoproteins and that for 

 this reason we do not know whether these acids are chemical individuals 

 or only a mixture of closely related simple nucleic acids. On the other 

 hand it is also possible that the simple nucleic acids originate from more 

 complex nucleic acid by cleavage because such cleavages are in fact 

 known. Such an assumption does not apply at least for the guanylic 

 acid from the pancreas as it is obtained from a compound protein with 

 only one base, namely guanine. 



All nucleic acids are amorphous, white, and have an acid reaction. 

 They are readily soluble in ammoniacal or alkaline water. They also 

 dissolve in concentrated acetic acid and form insoluble salts with copper 

 chloride and salts of the heavy metals, and as a rule insoluble basic 

 salts with the alkaline earths. Their solubility in water is very different. 

 Inosinic acid, for example, is very readily soluble in cold water while 

 #-guanylic acid is soluble with difficulty. The complex nucleic acids 

 are also soluble with difficulty in cold water. The solution of their 

 alkali combination is not as a rule precipitated by acetic acid but is 

 precipitated by a slight excess of hydrochloric acid, especially in the pres- 

 ence of alcohol. The nucleic acids soluble in dilute acids give in such 

 solution a precipitate with proteins, which are considered as nucleins. All 

 nucleic acids are insoluble in alcohol and ether. They do not give either 

 the biuret test or MILLON'S reaction. The nucleic acids are optically 

 active and, with the exception of inosinic acid (GAMGEE and JONES) 

 and of guanylic acid (LEVENE and JACOBS 1 ), are dextro-rotatory. 



1 Gamgee and Jones, Proc. Roy. Soc., 72; Levene and Jacobs, Journ. of biol. 

 Chem., 12. 



