C-13-NMR OF THE DEOXYRIBOSE SUGARS IN 4 DNA OLIGONUCLEOTIDE DUPLEXES - ASSIGNMENT AND STRUCTURAL FEATURES

Natural-abundance C-13-NMR spectra have been obtained for four self-co mplementary DNA oligonucleotides: [d(TAGCGCTA)](2), [d(GGTATACC)](2), [d(CG)(3)](2), and [d(TCGCG)](2); this paper focuses on the deoxyribos e resonances. Assignments were made by a combination of the two-dimens ional proton-detected heteronuclear correlation experiment and compari son of 1D spectra, accounting for P-31 coupling, bask composition, and similarities in chemical shift versus temperature profiles (delta vs T). Large shielding and deshielding of the sugar resonances (between 2 .0 and -1.9 ppm) are observed upon thermal dissociation of the duplex. The shapes of the delta vs T profiles correlate strongly with the pur ine/pyrimidine nature of the base attached at C1' in these duplexes th at have a substantial fraction of residues within alternating purine-p yrimidine sequences. The correlation is primarily associated with chan ges in the equilibrium distribution of furanose pseudorotational state s that may arise in part from the relief of interstrand purine-purine steric clashes.