The composition of the pentose nucleic acids of yeast and pancreas.

The historically understandable attempts to simplify the problem of nucleic acid structure by the formulation of the tetranucleotide hypot.hesis have found their classical exposition in Levene’s monograph of 1931 (1). The same tendencies are expressed, less precisely, in statements found in many text-books according to which the nucleic acid unit, having a molecular weight of about 1200, contains four different bases (two purines and two pyrimidines) in equimolecular proportions. With the growing recognition of the complex and macromolecular character of the nucleic acids the necessity for the postulation of these hypothetical units vanished and it became possible to consider nucleic acids as substances comparable to the proteins in intricacy and, perhaps, even in specificity. Our present knowledge of the structure of nucleic acids has been reviewed repeatedly in the recent past (24). Other relevant aspect,s also have been considered (5, 6). The method for the quantitative estimation of individual purines and pyrimidines in mixtures of these bases, presented in the preceding paper (7), has made possible a new approach to the study of the composition of nucleic acids. The present communication describes the application of these procedures to a study of the distribution of the nitrogenous constituents of the pentose nucleic acids of yeast and pig pancreas and includes a consideration of aspects related to this problem, such as the mechanisms of the acid hydrolysis of these compounds. Other accounts, to be submitted shortly, will deal with the composition of desoxypentose nucleic acids. The results reported here will, later in this paper, be correlated with the findings of previous workers.