The mysterious indefiniteness which was attached, only a few years ago, to the then newly coined word "nuclein" is rapidly disappearing with the advent of new and precise information. The word itself is being abandoned for the expression "nucleoprotein," which is intended to designate the salt-like combinations of protein and nucleic acids.1 The latter can be disintegrated into a group of well-defined substances-purin and pyrimidin base, sugars, phosphoric acid-which may properly be looked on as the chemical units out of which they are built up, precisely as proteins are constructed out of amino-acid units. The purin bases, adenin and guanin (with their derivatives hypoxanthin and xanthin) have been the subject of exceptional interest because of their precursor relationship to uric acid.
Although the nucleic acids can be split up into these primary groups through the agency of vigorous hydrolytic procedures, Levene and his collaborators in the Rockefeller Institute have
NEW ASPECTS OF PURIN METABOLISM. JAMA. 1914;LXIII(16):1397-1398. doi:10.1001/jama.1914.02570160063026