Physical State of Deoxyribonucleic Acid in Rat Thymus Homogenates

Abstract

IN a recent communication, Anderson¹ has shown that when the thymus of the freshly killed rat is homogenized and then dissolved in M sodium chloride, extremely viscous solutions are obtained. It is clear that the high viscosity is primarily due to the deoxyribonucleic acid present, but it is much greater than that of solutions containing the same amount of deoxyribonucleic acid isolated by the usual technique. To explain this discrepancy, Anderson suggested that in freshly prepared tissue homogenates deoxyribonucleic acid has a much higher molecular weight than the chemically isolated substance. This explanation is valid only if the deoxyribonucleic acid is molecularly dispersed in the tissue homogenates and does not interact with any other compound present. Using rat thymus homogenized in 0.14 M sodium chloride, filtered through nylon cloth and then diluted with an equal volume of 2 M sodium chloride, evidence has been obtained which suggests that the deoxyribonucleic acid is probably present in the form of aggregates in which nucleic acid molecules are cross-linked by protein bridges.