6,7-Dimethyllumazine as a potential ligand for selective recognition of adenine opposite an abasic site in DNA duplexes

6,7-Dimethyllumazine more selectively binds to adenine (A) base opposite the abasic site in DNA duplexes (5'-Tcc AG (X) under bar GCA AC-3'/3'-AGG TC (N) under bar CGT TG-5', (X) under bar = AP site (Spacer C3), (N) under bar = A, T, C and G) than the other three nucleobases with a dissociation constant K-d of ca. 1.0 mu M; substituted methyl groups enhance the binding affinity to A and the selectivity for A over T, compared to the parent molecule, lumazine.