On the denaturation of deoxyribonucleic acid: II. Effects of concentration

Abstract

In continuation of previous studies the denaturation of DNA and the reversal of this process have been studied in 6 preparations of purified DNA from calf thymus, Escherichia coli, and Bacillus subtilis. The denaturation was produced by the dialysis of DNA solutions in the cold against distilled water and reversed by the subsequent addition of salt. The loss and the restoration of secondary structure were followed by means of thermal denaturation in water and in saline. The maximum hyperchromicity attained by the denaturation of DNA through dialysis, heating, or a combination of these procedures amounts to an increase of 38 % of the initial ε(P). Both deand renaturation are dependent upon concentration. Concentrated DNA solutions are denatured by dialysis more rapidly than dilute solutions. The dilution of concentrated dialysed solutions with water produces a rise in ε(P) and diminishes the amount of DNA restorable by the addition of salt. The dialysis of very dilute DNA solutions (around 20 μg/ml) produced no spectral evidence of denaturation.