From explicit solvent molecular dynamics simulations, we probe the existence of two stable and competitive interaction modes between an alternating poly(dA-dT) decamer and benzophenone: a minor groove adduct and a double insertion structure in which the central base pair is ejected, with hydrogen bonding with proximal groups, locking the DNA-drug complex. The extensive analysis of non-covalent interactions provides a rationale for the existence of this mode, never reported yet between DNA and any organic photosensitizer. We evidence a highly characteristic signature in our simulated circular dichroism spectra that may provide useful guidance for the future experimental efforts, as well as for theoretical investigations aiming at elucidating the energy transfer mechanism between benzophenone and thymines