Determination of the DNA sugar pucker using sup 13 C NMR spectroscopy

Solid-state {sup 13}C NMR spectroscopy of a series of crystalline nucleosides and nucleotides allows direct measurement of the effect of the deoxyribose ring conformation on the carbon chemical shift. It is found that 3{prime}-endo conformers have 3{prime} and 5{prime} chemical shifts significantly (5-10 ppm) upfield of comparable 3{prime}-exo and 2{prime}-endo conformers. The latter two conformers may be distinguished by smaller but still significant differences in the carbon chemical shifts at the C-2{prime} and C-4{prime} positions. High-resolution solid-state NMR of three modifications of fibrous calf thymus DNA shows that these trends are maintained in high-molecular-weight DNA and confirms that the major ring pucker in A-DNA is 3{prime}-endo, while both B-DNA and C-DNA are largely 2{prime}-endo. The data show that {sup 13}C NMR spectroscopy is a straightforward and useful probe of DNA ring pucker in both solution and the solid state.