摘要：

The denaturation of DNA by heat and acid has been studied by means of potentiometric titration. Titration curves have been determined at various temperatures and ionic strengths. Denaturation occurs during the steep inflection of the forward (neutrality → low pH) titration curve; the extent of denaturation depends on the proportion of this inflection which is titrated. Before denaturation begins there are some hydrogen bonds which are reversibly broken and healed. When a critical number of bonds are cleaved, denaturation sets in. This number depends on the temperature, ionic strength and the solvent system. In the presence of urea, fewer groups must be titrated potentiometrically to cause denaturation; that is, the equilibrium intact broken bonds is shifted to the right for any given temperature and ionic strength. It is also concluded that the effects of heat and acid, when acting simultaneously, are additive.

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