Nucleic Acids Research, Vol 26, Issue 6 1503-1508, Copyright © 1998 by Oxford University Press
AV Vologodskii, X Yang and NC Seeman
We have induced a local conformational transition by positive torsional
stress in small synthetic circular DNA molecules containing cruciforms with
immobile or tetramobile branched junctions. The immobile species correspond
to the extruded and intruded extrema of the tetramobile junction. Under
normal conditions the sequences of all the branched species prevent them
from being re-absorbed into the circle. We have induced positive stress by
addition of ethidium to the circle, in a low ionic strength medium.
Alterations in gel electrophoretic mobility under increasing concentrations
of ethidium suggest that the cruciforms undergo a transition under
torsional stress. The product of this transition contains mispaired
nucleotides, but interwound backbones. By comparing the electrophoretic
mobilities of circles containing these structures with that of a completely
complementary circle of the same length, we conclude that the twist in the
mispairing region is similiar to that of completely paired species.
ARTICLES
Non-complementary DNA helical structure induced by positive torsional stress
Department of Chemistry, New York University, New York, NY 10003, USA.
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