title: The flexibility of A-form DNA.
abstract: We have determined the rise per base pair and persistence length of A-form DNA in trifluoroethanol solutions for fragments 350-900 base pairs in length that best describe rotational diffusion coefficients determined by transient electric birefringence. The 2.6 A spacing between base pairs found in crystal and fiber A-form structures is preserved in solution. The persistence length is about 1500 A, or about three times longer than for B-form DNA. There is no apparent electrostatic contribution to the persistence length in the salt concentration range 0.2-2.0 mM Na cacodylate. This suggests an even closer association between DNA and its neutralizing counterions than predicted by condensation theory, perhaps due to a sheath of trifluoroethanol excluded water surrounding the A-form helix.
authors.affiliation: Laboratory of Chemical Physics, NIDDK, National Institutes of Health, Besthesda, Maryland 20892.
authors.forename: E
authors.initials: E
authors.lastname: Charney
authors.forename: H H
authors.initials: HH
authors.lastname: Chen
authors.forename: D C
authors.initials: DC
authors.lastname: Rau
mesh_terms: D001718:Birefringence; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry*; D006801:Humans; D009690:Nucleic Acid Conformation; D014783:Viscosity
chemical_list: D004247:DNA