Effect of screening on the transport of polyelectrolytes through nanoporesG. Oukhaled1, L. Bacri1, J. Mathé1, J. Pelta2 and L. Auvray1
1 Institut de Chimie des Matériaux Paris-Est, équipe Matériaux Polymères aux Interfaces, CNRS-UMR 7182, Université d'Évry - Bd F. Mitterrand, 91025 Évry, France, EU
2 Groupe Micro-environnement et Comportements Cellulaires, Université de Cergy-Pontoise - 2. av. A. Chauvin, 95302 Cergy-Pontoise Cedex, France, EU
received 3 July 2007; accepted in final form 26 March 2008; published May 2008
published online 7 May 2008
We study the transport of dextran sulfate molecules (Mw = 8000 Da) through a bacterial -hemolysin channel inserted into a bilayer lipid membrane submitted to an external electric field. We detect the current blockades induced by the molecules threading through one pore and vary the ionic strength in an unexplored range starting at 10-3 M. In the conditions of the experiment, the polyelectrolyte molecules enter the pore only if the Debye screening length is smaller than the pore radius in agreement with theory. We also observe that large potentials favour the passage of the molecules. The distribution of blockade durations suggests that a complex process governs the kinetics of the molecules. The dwelling time increases sharply as the Debye length increases and approaches the pore radius.
82.37.-j - Single molecule kinetics.
82.35.Rs - Polyelectrolytes.
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