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-complementary DNA oligonucleotides: [d(TAGCGCTA)](2), [d(GGTATACC)](2), [d(CG)(3)](2), and [d(TCGCG)](2); this paper focuses on the deoxyribose resonances. Assignments were made by a combination of the two-dimensional proton-detected heteronuclear correlation experiment and comparison 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 purine/pyrimidine nature of the base attached at C1' in these duplexes that have a substantial fraction of residues within alternating purine-pyrimidine sequences. The correlation is primarily associated with changes in the equilibrium distribution of furanose pseudorotational states that may arise in part from the relief of interstrand purine-purine steric clashes.