15N and 13C nuclear magnetic resonance of deoxynucleotide monophosphates. I. Protonation of d(CpG) in dimethylsulfoxide

The 15N and 13C chemical shifts of the sodium salt of deoxycytidylyl-3'-5'-guanosine have been measured in dimethylsulfoxide in the presence of variable amount of CF3COOH. N3(cyt) is protonated first, followed by n7(gua) and the phosphate anion. These results vary from those reported for the binding of the methylmercuric cation to d(CpG).