Evidence for the existence of hydrogen-bonded cyclic tetramers in aqueous solutions of tetramethylammonium guanosine 5'-monophosphate.

Proton NMR and FTIR measurements have shown that the formation of stable, interbase hydrogen-bonded species of 5'-GMP in aqueous solutions of the tetramethylammonium salt can occur without the subsequent formation of ordered, slowly-exchanging structures or base stacking. Analysis of the NMR data is in agreement with an equilibrium mixture of monomers, dimers and cyclic tetramers. The association constants and amino proton chemical shifts are reported for these species. This is the first report that the cyclic tetramer structure exists as a discrete species in 5'-GMP solutions.