title: Interaction of water with oriented DNA in the A- and B-form conformations.
abstract: High resolution 2H nuclear magnetic resonance (NMR) was used to investigate the interaction of D2O with solid samples of uniaxially oriented Li-DNA (B-form DNA) and Na-DNA (A- and B-form DNA). At low levels of hydration, 0 approximately 4 D2O/nucleotide, the 2H spectra shows a very weak (due to short T2) broad single resonance, suggestive of unrestricted rotational diffusion of the water. At approximately 5 or more D2O/nucleotide, the Li-DNA (B-form) spectra suddenly exhibit a large doublet splitting, characteristic of partially ordered water. With increasing hydration, the general trend is a decrease of this splitting. From our analysis we show that the DNA water structure reorganizes as the DNA is progressively hydrated. The D2O interaction with Na-DNA is rather different than with Li-DNA. Below 10 D2O/nucleotide Na-DNA is normally expected to be in the A-form, and a small, or negligible splitting is observed. In the range 9-19 D2O/nucleotide, the splitting increases with increasing hydration. Above approximately 20 D2O/nucleotide Na-DNA converts entirely to the B-form and the D2O splittings are then similar to those found in Li-DNA. We show that the complex Na-DNA results obtained in the range 0-20 D2O/nucleotide are caused by a mixture of A- and B-DNA in those samples.
authors.affiliation: Department of Chemistry, University of California, San Diego, La Jolla 92093-0342.
authors.forename: R
authors.initials: R
authors.lastname: Brandes
authors.forename: A
authors.initials: A
authors.lastname: Rupprecht
authors.forename: D R
authors.initials: DR
authors.lastname: Kearns
mesh_terms: D004247:DNA; D003903:Deuterium; D017666:Deuterium Oxide; D008094:Lithium; D009682:Magnetic Resonance Spectroscopy; D008433:Mathematics; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation; D012964:Sodium; D014867:Water
chemical_list: D014867:Water; D004247:DNA; D008094:Lithium; D012964:Sodium; D003903:Deuterium; D017666:Deuterium Oxide