The Structure of Thymonucleic Acid

The earlier work on thymonucleic acid by Levene and Mandell and by Levene and Jacobs2 led to the isolation of monophosphoric esters of pyrimidine nucleosides and diphosphoric esters of pyrimidine nucleosides. These observations were corroborated by Thannhauser and coworkers.3 In a recent publication Levene and London4 reported the isolation of a guanine nucleoside and the present paper contains a report on the isolation of three additional nucleosides, namely hypoxanthine, thymine, and cytosine nucleosides. The hypoxanthine nucleoside is undoubtedly derived from the adenine nucleoside inasmuch as the yeast nucleic aoid digested in the same manner as the thymonucleic acid gave inosine in place of adenosine. The newer findings definitely confirm the formulation for the thymonucleic acid given by Levene, in 1921, which is but a modification of the one given by Levene and Jacobs, in 1912. In one essential detail the formulation of Levene and Jacobs and of Levene needs revision; namely, the sugar entering in the structure of thymonucleic acid is now found to be not a hexose but a desoxypentose. With this correction, the formulation of the structure of thymonucleic acid becomes as follows: