CONFORMATION, HYDROGEN-BONDING AND AGGREGATE FORMATION OF GUANOSINE 5'-MONOPHOSPHATE AND GUANOSINE IN DIMETHYLSULFOXIDE

The tetrabutylammonium salt of guanosine 5'-monophosphate (5'-GMP) dis solves in DMSO-d(6) forming aggregated species which exhibit some prop erties of reverse micelles. H-1 NOESY experiments show that the 5'-GMP adopts the syn conformation about the glycosidic bond. Molecular mech anics calculations reveal a stable structure with this conformation in which the phosphate group and the amino group of the base are in clos e enough proximity to hydrogen bond. In contrast inosine 5'-monophosph ate in DMSO-d(6), which has no NH2 group for hydrogen bond stabilizati on of the syn conformation, is shown by NMR to have the anti structure . Guanosine in DMSO-d(6) behaves differently from 5'-GMP. Guanosine ad opts the anti conformation and forms a symmetric dimer via hydrogen bo nding between the N3 and NH2 of the bases.