Fractionation of Deoxyribonucleoprotein by Successive Extraction with Constant Salt Concentration

Abstract

IN recent papers Chargaff and his collaborators¹, and Brown and Watson², have shown the possibility of obtaining nucleic acids (DNA) of varying composition from deoxyribonucleoprotein. Chargaff's fractionation was achieved by successive extractions of nucleoprotein with salt solutions of increasing strength, after the nucleoprotein had been precipitated by a mixture of chloroform and n-octanol. This yielded a series of nucleic acid fractions containing progressively increasing quantities of adenine and thymine. Chargaff has suggested that this fractionation may arise from the existence of bonds of varying stability, between the protein and the nucleic acid, which are broken progressively with increasing salt concentration. It may be noted that in the observations quoted, although fractions of differing composition were undoubtedly obtained, there were marked irregularities in the way in which the composition of the fractions varied with the salt-concentration used in extraction. This suggested to us that some other variable may have had a significant effect on the results obtained.