NMR Lanthanoid-probe Analyses of Conformational Properties of 8,2′-S-Cycloadenosine 3′-Monophosphate in Aqueous Solution

Abstract

Abstract The advanced method of NMR lanthanoid-probe analyses was used for studying the molecular conformations of 8,2′-anhydro-8-thio-9-β-d-arabinofuranosyladenine (8,2′-S-cycloadenosine) 3′-monophosphate in aqueous solution. From the observed ratios of Pr(III)-induced shifts, Gd(III)-enhanced relaxation rates as well as vicinal spin-coupling constants, the most probable values (and standard deviations) of the fractional populations of the local conformations for the C5′–C4′ bond, sugar ring, C3′–O3′ bond, and O3′–P bond and the internal rotation angles of the two forms about the C3′–O3′ bond were determined by the program COFLEM. The internal rotation equilibrium about the C3′-O3′ bond was found to be interrelated with the puckering of the sugar ring. The advanced lanthanoid probe method is thus useful for the analyses of the conformational characteristics of cyclonucleotides as well as of unmodified nucleotides in aqueous solution.