| Abstract
| - A systematic study of the CH/π interactions of methane with the purine and pyrimidine bases of nucleicacids and with the lateral chains of the four natural aromatic amino acids has been carried out for the firsttime. The MPWB1K/6-31+G(d,p) method has shown to be adequate for the study of these weak interactionsin which dispersion forces play a main role. It has been shown that two different kinds of clusters exist,depending on whether one or two CH bonds point to the aromatic system. The latter one, which we havecalled bifurcated, is usually more stable. With regard to aromatic amino acids, our calculations agree withexperimental data in the fact that tryptophan leads to the strongest interaction, while hystidine leads to theweakest one. In the case of nucleic acid bases, the differences in binding energies are not large. This isspecially true for thymine and uracil, showing that these two bases have a similar acceptor character in CH/πinteractions.
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