Internal motions in deoxyribonucleic acid II

Abstract

The 1H, 31P and 13C NMR parameters of monodisperse DNA fragments 260 and 140 base pairs long were measured as a function of temperature and solvent viscosity. On the basis of these measurements, within a rodlike DNA helix, the base planes, the deoxyribose sugar and the sugar-phosphate backbone all experience large fast internal motions. The best fit of the data to a 2-state model for internal motion specificies for the internal motions the following amplitudes (A) and correlation times (.tau.) for the base planes: A = .+-.20.degree. and .tau. = 1 .times. 10-9 s; for position 2'' of the deoxyribose sugar, A = .+-.20 to .+-.33.degree. and .tau. = 1 .times. 10-9 s; for the P-H vectors of the sugar-phosphate backbone, A = .+-.27.degree. and .tau. = 2.2 .times. 10-9 s.