The intermolecular dimer potential for guanine.

The ab initio intermolecular potential of guanine has been developed with the help of a combination of symmetry-adapted perturbation theory and density functional theory (DFT). The resulting potential has been globally optimized to locate the guanine cluster structures up to tetramers. It has been found that the new potential is able to reproduce the known guanine cluster structures, especially the guanine quartet stabilized by Hoogsteen hydrogen bonds, in addition to new low-energy conformers. The performance of the potential was also compared with the AMBER force field as well as DFT-D and MP2 levels of theory. The model potential is in agreement with the ab initio methods and it shows a better performance compared to AMBER. Therefore, it can be further exploited in molecular dynamics or global optimizations to determine the structure and energy of much larger guanine clusters.