The B-A transition in superhelical DNA. |
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| Authors: | Krylov DYu V L Makarov and V I Ivanov |
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| Institution: | Engelhardt Institute of Molecular Biology, USSR Academy of Sciences, Moscow. |
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| 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. |
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