Study of neurotransmitter dopamine interaction with DNA by electrochemical and spectroscopic methods

Dopamine interaction with DNA has been studied using square-wave voltammetry (SWV), fluorescence, and absorption spectroscopy. The effect of dopamine on the binding of classical intercalating agents, such as acridine orange (AO), ethidium bromide (EtBr) as well as classical groove binding ligand Hoechst 33258 (H33258) was evaluated. The obtained results clarify the molecular mechanisms of dopamine interaction with DNA and reveal its potential competition for intercalation and minor groove binding sites which show that dopamine interacts with DNA by multimodal modes. On the basis of fluorescence measurements, the values of the binding constant (K) and the number of base pairs (n) per binding site were determined. It was revealed that the values of these binding parameters (K and n) depend on the ionic strength of the solution. Based on the changes of the binding parameters of AO, EtBr and H33258 with DNA in the absence and presence of dopamine, it was shown that the presence of the neurotransmitter reduces the affinity of these ligands toward DNA. The obtained data indicate that dopamine binds to DNA via intercalation and minor groove binding mechanisms, which leads to a decrease in the binding constants of these ligands with DNA. In the case of dopamine interaction with DNA in the presence of intercalators, the effect is especially pronounced for the strong (intercalation) binding mode of EtBr, as its binding constant with DNA in the presence of dopamine is significantly lower than that of AO.