DNA excimers

Here is our new paper: "Electronic excitation and structural relaxation of the adenine dinucleotide in gas phase and solution." In this article we looked at excited state relaxation and excimer formation between two stacked adenine molecules.

The new result of this study is that orbital interactions might play an important role that is often overlooked when excited state interactions are only considered in the framework of charge transfer or Frenkel excitonic states (similar to what we found for the naphthalene excimer  [JCTC 2012, 137, 22A514] ). And the force holding together the excimer may even have some parallels to chemical bonding. In the case of pyrimidine bases, actual bonds may be formed and dimerization occurs. This is of course not the case for adenine. But our results suggest that it is possible to interpret the excimer state between adenines in a similar framework only that (fortunately for us) no stable dimer can be formed.

Of course all computational results are speculative in such an area as you do not only need an accurate description of the excited states but also of the intermolecular interaction potential and the environment, which are difficult tasks even when considered by itself. So I am not claiming that this is the final solution. But I hope it is a step in the right direction.