Hydrogen-Bonding Patterns Observed inthe Base Pairs of Duplex Oligonucleotides

Watson-Crick base pairing in duplex structures utilises a unique combination of hydrogen bond donors and acceptors to stabilise the association. This stability contributes to the fidelity of replication. Non-Watson-Crick base pairs, mismatches or base pairs involving chemically modified bases adopt different patterns of hydrogen bond interactions sometimes utilising water molecules to stabilise the pairing and in some cases an argument can be put forward for C-H⋯O interactions as a contributing factor in the pairing and not just in mismatches. The different hydrogen bonding patterns deduced on the basis of single crystal x-ray diffraction studies are described. These hydrogen bonding patterns have implications for protein-nucleic acid interactions and for the modelling of nucleotide structures.