Conformational analysis of a covalently cross-linked Watson–Crick base pair model

Low-temperature NMR experiments and molecular modeling have been used to characterize the conformational behavior of a covalently cross-linked DNA base pair model. The data suggest that Watson–Crick or reverse Watson–Crick hydrogen bonding geometries have similar energies and can interconvert at low temperatures. This low-temperature process involves rotation about the crosslink CH2single bondC(5′) (ψ) carbon–carbon bond, which is energetically preferred over the alternate CH2single bondN(3) (φ) carbon–nitrogen bond rotation.