Deoxyguanosine-deoxyadenosine pairing in the d(C-G-A-G-A-A- T-T-C-G-C-G) duplex: Conformation and dynamics at and adjacent to the dG.dA mismatch site.

The dG.dA interaction at position 3 was monitored at the guanosine exchangeable H-1 and non-exchangeable H-8 protons and the non exchangeable adenosine H-2 proton. We demonstrate base pair formation between anti orientations of the guanosine and adenosine rings based on nuclear Overhauser effects observed between the H-2 proton of adenosine 3 and the imino protons of guanosine 3 (intra-base pair) and guanosines 2 and 4 (inter-base pair). The dG(anti).dA(anti) pairing should result in hydrogen bond formation between the guanosine imino H-1 and carbonyl O-6 groups with the adenosine N-1 and NH(2)-6 groups respectively.