[Nuclear magnetic resonance study of the conformation in nucleotides, oligonucleotides, and their analogs. I. Conformation of adenosine-3',5'-cyclic phosphate and its analogs in aqueous solutions].

Conformation in aqueous solution of adenosine-3',5'-cyclophosphate, 8-(beta-aminoethylamino) adenosine-3',5'-cyclophosphate, 8-(beta-oxiethylamino) adenosine-3',5'-cyclophosphate, 8-(carboxymethylamino) adenosine-3',5'-cyclophosphate and their non-cyclic analogs has been studied by NMR spectroscopy. The conformational situation in the model of dynamic equilibrium of sin- and anti-states has been described on the basis of spinlattice relaxation times and temperature dependences of chemical shifts. Adenosine-3',5'-cyclophosphate has been demonstrated to exist mainly in anti-conformation while 8-substituted analogs -- in sin-conformation. Equilibrium constants have been calculated for the compounds under study.