title: Determination of the syn-anti equilibrium of some purine 3':5'-nucleotides by nuclear-magnetic-relaxation perturbation in the presence of a lanthanide-ion probe.
abstract: The aqueous solution conformation of four purine 3':5'-nucleotides varying in their substituents at C-6 and C-8 has been studied using gadolinium(III) to perturb the proton relaxation times. The ribose conformations are inferred. All the nucleotides are best described as being in a dynamic equilibrium between syn and anti conformations and the position of this equilibrium is not dramatically affected by changing the substituent at C-6. These nucleotides in their neutral base form slightly favour an anti conformation. In the presence of a bulky methylthio group at C-8 the equilibrium is shifted towards a dominance from the syn conformation due to steric repulsion factors.
mesh_terms: D001665:Binding Sites; D000242:Cyclic AMP; D007289:Cyclic IMP; D005682:Gadolinium; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009712:Nucleotides, Cyclic
chemical_list: D009712:Nucleotides, Cyclic; D007289:Cyclic IMP; D005682:Gadolinium; D000242:Cyclic AMP