title: The B-A transition in superhelical DNA.
abstract: Relaxation of a DNA superhelical stress due to the B to A transition induced by trifluoroethanol has been studied by assessing the change of DNA orientation in a flow gradient. Using DNAs of different superhelical densities, a decrease in the winding angle during the B----A shift of DNA was found to be 1.5 degrees per base pair in solution. Accepting the winding angle for B-DNA in solution to be 34.1 degrees, that for A-DNA must have a value of 32.6 degrees which agrees with the X-ray data for A-DNA in the condensed state. The date obtained within the B-A transition interval make it possible to conclude that there is an increase in winding at each B/A junction, which is about 5 degrees per one junction.
authors.affiliation: Engelhardt Institute of Molecular Biology, USSR Academy of Sciences, Moscow.
authors.lastname: Krylov DYu
authors.forename: V L
authors.initials: VL
authors.lastname: Makarov
authors.forename: V I
authors.initials: VI
authors.lastname: Ivanov
mesh_terms: D004264:DNA Topoisomerases, Type I; D004270:DNA, Circular; D004996:Ethidium; D007700:Kinetics; D009690:Nucleic Acid Conformation; D010957:Plasmids
chemical_list: D004270:DNA, Circular; D004264:DNA Topoisomerases, Type I; D004996:Ethidium