The substitution mechanism of [RuIII(edta)(H2O)]- with DNA bases, nucleoside and nucleotides in aqueous solution revisited

The substitution reactions of [Ru-III(edta)(H2O)](-) (edta = ethylenediaminetetraacetate) with adenine, adenosine and the corresponding 5'-nucleotides (Nu), viz. adenosine-5'-monophosphate (AMP), adenosine-5'-diphosphate (ADP) and adenosine-5'-triphosphate (ATP), have been studied kinetically as a function of nucleotide concentration at various temperatures (5 to 30 degreesC) at a fixed pH of 4.6 to contribute to the mechanistic understanding of the binding of adenine base nucleotides. Based on the kinetic results, it is suggested that the binding of the 5'-nucleotides (AMP, ADP and ATP) takes place in a rapid nucleophile concentration-dependent step, followed by a concentration-independent ring-closure reaction. Kinetic data and activation parameters have been interpreted in terms of an associative mechanism and discussed in reference to the data reported before.