Calorimetric investigation of 5‐methoxytryptamine binding to DNA and poly(A)

It is well known that many aromatic molecules, e.g. acridine dyes, are able to stack with purine and pyrimidine bases in single stranded and double stranded nucleic acids [l-3] . The possibility that such a type of complex involving aromatic amino acids may play a role in the interaction between nucleics and proteins has been recently investigated by several groups. Particularly it has been demonstrated that this type of complex takes place with model compounds involving derivatives of aromatic acids such as amines [4-71 or oligopeptides [8-161. Whereas the enthalpy and entropy changes corresponding to the formation of stacked between several dyes and DNA are known [ 171, similar data for the complexes formed by aromatic amino acid derivatives and nucleic acids have not been reported yet. The knowledge of such values is necessary for a better description of the interaction phenomenon. We have recently determined, using circular dichroism measurements, the thermodynamic parameters for the binding amine derivative of tryptophan, S-methoxy tryptamine, to single stranded poly(A) [ 161 and to DNA [ 1 S] . In this paper results are reported from direct calorimetric measurements on the binding of 5methoxytryptamine to poly(A) and DNA.