STRETCHING DNA has produced an “inside-out” form of the molecule which may
fleetingly exist in cells.
Jean-Fran莽ois Allemand of the 脡cole Normale Sup茅rieure in Paris
led a team that attached one end of a DNA molecule to a glass surface and the
other to a magnetic bead. The molecule was then stretched and twisted using
magnets. The resulting structure was more tightly coiled than ordinary DNA,
forcing the bulky bases to flip to the outside of the helix (Proceedings of
the National Academy of Sciences, vol 95, p 14 152).
Allemand says he suspects that similar structures may exist in human cells.
When DNA undergoes transcription and replication, it is subjected to similar
forces.
