Long-range imino proton-13C J-couplings and the through-bond correlation of imino and non-exchangeable protons in unlabeled DNA

Thanks to rather large (5-9 Hz) long-range imino proton-C-13 J-couplings, heteronuclear correlation experiments in H2O provide unambiguous assignment of imino protons by intranucleotide through-bond connectivities to guanosine H8 and thymidine CH3 protons, or sequence-specific assignment of non-exchangeable protons when the imino protons are identified independently. This method is demonstrated in the Dickerson dodecamer [d(CGCGAATTCGCG)](2) and in a human telomeric fragment of 22 nucleotides.