The determination of the total deoxyribose of deoxyribonucleic acid.

Although several methods (1-5) are used for the determination of deoxyribonucleic acid, none is without some limitations. For example, procedures (1) that depend on the analysis of phosphate in fractionated materials are of limited sensitivity. The use of the absorption at 260 rnp as a measure of deoxyribonucleic acid (2) does not provide a procedure giving readily comparable values for different biological materials. The mole fraction, nc, of the most important bases in deoxyribonucleic acid are shown in Table I in which a calculated summated molar absorbancy index aMdsO = Z&aMi, based on the molar absorbancy index aMi of each base (lo), appears in the last column. A marked difference (7.9 to 9.4 X lo”) in the molar absorbancy index of the several materials is observed even though the more recently discovered bases are not considered. Furthermore, it is well known that the absorbancy of deoxyribonucleic acid near 260 mp in the ultraviolet depends to a great extent on the configuration of the molecule. Analytical procedures based on the indole color reaction have been useful in studying tissue deoxyribonucleic acid. Although this method is of a high order of sensitivity, the results have often been more relative rather than absolute since the kinetics of hydrolysis and color formation have not been understood completely. Experiences gained in the present investigation of the indole color method as applied to rabbit aorta confirmed the disparity indicated by the results of numerous investigations (11-15) and prompted a kinetic study of the method, the findings of which are being reported. From this study, some of the optimal conditions for the calorimetric determination of deoxyribonucleic acid by the indole color method have been determined which now permit a quantitative determination of total deoxyribose.