title: Density functional study of adenine tetrads with N6-H6...N3 hydrogen bonds.
abstract: The structure and energy of A-tetrads with N6-H6...N3 H-bonds was studied using B3LYP and BH&H density functional theory. The planar A-tetrad with C(4h) symmetry is more stable than the nonplanar structures at C4 and S4 symmetry. This structure corresponds to a local energy minimum. The energies of the structures with N6-H6...N1 and N6-H6...N7 H-bonds studied previously are of similar magnitude. Structures of A-tetrad complexes with sodium and potassium were most stable at S4 symmetry, and similarly, sandwich complexes consisting of two tetrads and a single cation were most stable at S8 symmetry. Relative energies of sandwich complexes with different symmetries obtained with the B3LYP and BH&H methods were quite different. BH&H overestimates the interaction energies between hydrogen-bonded neighbor bases relative to B3LYP.
authors.affiliation: Revotar Biopharmaceuticals AG, Neuendorfstrasse 24a, D-16761 Hennigsdorf, Germany. m.meyer@ revotar-ag.de
authors.forename: Michael
authors.initials: M
authors.lastname: Meyer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Sühnel
mesh_terms: D000225:Adenine / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D007364:Intercalating Agents / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry
chemical_list: D007364:Intercalating Agents; D006859:Hydrogen; D012964:Sodium; D000225:Adenine; D009584:Nitrogen; D011188:Potassium