2-aminopurine (2AP) is an analogue of adenine that is employed as a fluorescent probe in studies of nucleic acid.  The fluorescence quantum yield of 2AP is decreased upon insertion into duplexes via mechanisms that continue to be an active area of scientific debate.  The excited states of ?-stacked dimers with 2AP were studied using ab initio methods, specifically configuration interaction singles with second order perturbative theory corrections.  Relaxation on the S1 surface of the dimers yielded conical intersections between the ground and first excited states.  Conical intersections are regions of degeneracy between potential energy surfaces that facilitate nonradiative excited state decay, thus leading to fluorescence quenching.  The conical intersections are accessed via strong distortions of the six-membered rings in the native bases, and interbase bonding character is observed in all systems except guanine.  These photophysical features may contribute to the decreased emission of 2AP in nucleic acid.

Conical intersections in [prod]-stacked nucleobase dimers containing 2-aminopurine

244th National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.