Density functional study of ribose and deoxyribose chemical shifts

Density functional chemical shielding calculations are reported for methyl beta-D-2-deoxyribofuranoside and for methyl beta-D-ribofuranoside, models for the deoxyribose and ribose sugars in nucleic acids. The variation of the chemical shielding as a function of the sugar ring conformation is reported, as well as the influence of the ring conformation on the chemical shift anisotropy. The calculated chemical shieldings are sensitive to the puckering of the sugar ring. The value of the exocyclic torsion angles, particularly gamma(05'-C5'-C4'-C3'), are also found to influence the chemical shielding of the ring atoms. The chemical shielding of the C3' carbon is the most sensitive to the sugar ring pucker, with a variation of 10 ppm between the C3' endo and C2' endo conformations. H3' and H4' hydrogen shieldings vary by 0.4-0.6 ppm between the C3' endo and C2' endo conformations. Chemical shift anisotropies at C1' and C3' are strongly influenced by sugar pucker. Our results agree well with experimentally reported values of chemical shifts in methyl beta-D-2-deoxyribofuranoside and methyl beta-D-ribofuranoside. They also agree with observed solid-state correlations between C3' and C5' chemical shift and sugar ring pucker and point to new methods for the analysis of nucleic acid conformation in solution.