New experimental data were obtained by means of circular dichroism, melting, renaturation, and kinetic experiments, upon Cu2+ binding to DNA, poly dAT, and poly dGdC. They enable us to propose a model of binding giving a satisfactory explanation to all of the data found in the literature. Two types of binding sites are proposed: (a) a “sandwich” of Cu2+ between two adjacent G‐C pairs giving a charge‐transfer complex, and (b) a chelate between a phosphate group and a nitrogen atom of the bases (N7 of guanine and N3 of cytosine at room temperature, N3 of adenine after thermal opening of A‐T pair). Type (a) stabilizes the helix and keeps the two strands linked. Type (b) destabilizes the helix and explains why the kinetic rate of renaturation is the same as that of copper release.
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Richard et al. (1973) studied this question.
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