Hydrogen-Bonding Interactions of 8-Substituted Purine Derivatives

Hydrogen bondingbetween nucleobases is a crucial noncovalent interactionfor life on Earth. Canonical nucleobases form base pairs accordingto two main geometries: Watson-Crick pairing, which enablesthe static functions of nucleic acids, such as the storing of geneticinformation; and Hoogsteen pairing, which facilitates the dynamicfunctions of these biomacromolecules. This precisely tuned systemcan be affected by oxidation or substitution of nucleobases, leadingto changes in their hydrogen-bonding patterns. This paper presentsan investigation into the intermolecular interactions of various 8-substitutedpurine derivatives with their hydrogen-bonding partners. The systemswere analyzed using nuclear magnetic resonance spectroscopy and densityfunctional theory calculations. Our results demonstrate that the stabilityof hydrogen-bonded complexes, or base pairs, depends primarily onthe number of intermolecular H-bonds and their donor-acceptoralternation. No strong preferences for a particular geometry, eitherWatson-Crick or Hoogsteen, were found.