David Bensimon
Laboratoire de Physique Statistique de l'Ecole
Normale Sup\'{e}rieure
24, rue Lhomond -- 75231 Paris Cedex 05,
France
The possibility to manipulate a single DNA
molecule has opened a new vista on the study
of its interactions with structural and regulating
proteins. We shall review the existing techniques
to stretch and twist single DNA molecules
and will compare this methodology with the
well known patch-clamp technique that has
allowed the study of single channels for
the past 20 years. The possibility to observe
individual molecules allows for a better
characterization of their enzymatic cycle
as the thermodynamic parameters and their
distribution are thus made available.
We shall see how this program can be implemented
in a few examples: DNA-polymerases, helicases
and topoisomerases.