"Matière et Systèmes Complexes"
2 juillet juin 2007 à 11h30
Bâtiment Condorcet, 4ème
étage, salle 454 A.
(MSC, Université Paris-Diderot)
Transport of one single polymer molecules through one single nanopore
used electrical recording to detect the passage of single polymer
molecules: a single 2 nm α-hemolysin pore is allowed to assemble
into a lipid bilayer separating two chambers filled with a conductive
solution at different voltages. During the passage of one single
polymer molecules, the ion current flowing through the channel is
mostly blocked, indicating the presence of polymer inside the channel.
The analysis of these blockades gives us informations on the dynamics
and the structure of the various polymers.
studied the translocation of large neutral polymers (PEG with gyration
radius from 5 to 20 nm well above the 2 nm pore size), which is
possible only if the monomer concentration (in the semi-dilute range)
is larger than a well-defined threshold. The dynamic of translocation
appeared to be modified, suggesting a reptation mechanism. Similarly,
the passage of charged polymers is only possible if the ionic strength
of the solution is high enough. In both cases, the correlation length
or screening length of the bulk polymer solution has to be smaller than
the pore diameter to allow the polymer passage.
structure of the polymer can also be discriminated by this technique;
we will present some new results on diblock copolymers.
demonstrated by Bayley, we will show how to decrease the size of the
pore with a molecular adapter. It allowed us to increase the electrical
resolution and then to observe the translocation of small chains of
polymers (malto-triose) which cannot be detected with the large ionic
α-hemolysin channel. I will discuss also the translocation of protein