13C-NMR of the deoxyribose sugars in four DNA oligonucleotide duplexes: assignment and structural features

Natural-abundance 13C-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 31P coupling, base 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.