Nucleic Acids 



WALTER JOISTES 



BALTIMORE 



/ Chemical Part 



By a tedious manipulation it is possible to isolate from animal and 

 plant tissues an organic acid, rich in both phosphorus and nitrogen, whose 

 decomposition products are so far characteristic that not one of them is 

 identical with any known decomposition product of a carbohydrate, a pro- 

 tein or a fat (Altman, 1889), (Osborne and Harris, 1002), (Kossel, 

 (a), (6), 1879, 18SO). The substance has been prepared from meta- 

 morphosed cell nuclei (Miescher, 1897), and as the amount of it that is 

 obtainable from a tissue is proportional to the richness of the tissue in 

 cell nuclei, it is properly regarded as a nuclear constituent and called 

 nucleic acid. 



Nucleic acid cannot be prepared sufficiently pure for chemical analysis, 

 so that its chemical composition has not been directly found. This can be 

 inferred, however, from a summation of its unique decomposition products. 

 But chemical composition, physical properties and other considerations 

 pertaining to nucleic acid as such, are matters about which, in the present 

 state of our knowledge, physiology is little concerned. It is the decom- 

 position products that are of importance, and these decomposition prod- 

 ucts are the same whether they are produced by chemical action outside 

 of the body or by physiological agents present in the tissues; so that 

 a discussion of the chemical decomposition of nucleic acid will disclose its 

 metabolic possibilities. 



Plant Nucleic Acid 



It was formerly supposed that a multiplicity of nucleic acids exist, 

 and that each tissue contains its individual substance of this class. But 

 without entering into the obscure and contradictory older contributions, 

 it is safe to state that everything known is in accordance with the assump- 

 tion that there are two, and only two, nucleic acids in nature : one is 

 obtainable from plant tissues (yeast nucleic acid) (Kossel, 1893), 

 and the other is obtainable from animal tissues (thymus nucleic 



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