DNA possesses a highly structured state, a double helix, along which base
pairs are parallel to each other and equidistant with their neighbours.
Between two successive base pairs, a planar aromatic molecule may intercalate.
As a consequence, the energy level of the DNA/organometallic compound are changed and in some cases,
one may obtain a fluorescent complex. But, moreover, the overall structure of DNA changes upon
intercalation and, in vivo, may lead to a change of the cell machinery. This change may
be exploited in order to design anti-cancerous compounds. We are interested in the interaction of
DNA with Ruthenium- organometallic molecules, and we study the structure of the resultant complex.
We have developed a light absorption titration technique that allows to determine the sequence of interactions involved in the interactions between DNA and these compounds. In particular, we seek to determine whether intercalation competes with other types of interaction. We have observed that, if, at low concentration of ruthenium compounds, the intercalation dominates the interaction, at higher concentrations, another mode of interaction develops, that involve electrostatic interactions.