Guanine and adenine-amino acids interactions: An ab initio study

Ab initio calculations using an STO-3G Gaussian basis set are performed in order to obtain the binding energy to the 06 and N7 of guanine of such amino acid models as the guanidinium ion for arginine, the ammonium ion for lysine, the methanol for serine, and the formamide for glutamic acid. The binding of formamide to adenine is also investigated. The charged ions exhibit a much higher binding energy to the bases, as expected, than the uncharged molecules. The order of binding strength is NH > guanidinium+ > formamide > methanol, and for formamide, guanine > adenine.