Conformational analysis of brominated pA2'-5'A2'-5'A analogs. An NMR and model-building study.

NMR and model-building studies were carried out on pA2'-5'A2'-5'A and analogs in which one or more of the A residues were replaced by 8-bromoadenosine. Chemical shifts, coupling constants and NOE data were used to obtain structural information. The N/S equilibrium constant of the ribose rings as well as the phase angles and puckering amplitudes were determined from the experimental coupling constants with the aid of an improved version of the PSEUROT program.