Poly(dA-dT) has a right-handed B conformation in solution: a two-dimensional NMR study.

The structure of poly(dA-dT) molecules in solution has been probed by using two-dimensional nuclear Overhauser effect spectroscopy. Cross-relaxation patterns arising from internucleotide and intranucleotide interactions are used to assign the sugar proton resonances and to deduce various structural features. The numerous proton-proton interactions that are observed indicate that poly(dA-dT) is a right-handed helix with a B-type conformation. Both the adenine and thymine nucleotides are in an anti conformation. Although slight differences in the purine-sugar and pyrimidine-sugar intranucleotide interactions are observed, the large differences in the sugar pucker of the adenine vs. thymine nucleotide suggested by some models [Klug, A., Jack, A., Viswamitra, M. A., Kennard, O., Shakked, Z., & Steitz, T. A. (1979) J. Mol. Biol. 131, 669-680] are not evident in the solution structure of poly(dA-dT). In the low-temperature spectra there is unexpected evidence for cross-strand AH2-AH2 interactions.