Computing numerically the access resistance of a pore

The access resistance (AR) of a channel is an important component of the conductance of ion channels, particularly in wide and short channels, where it accounts for a substantial fraction of the total resistance to the movement of ions. The AR is usually calculated by using a classical and simple ex...

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Bibliographic Details
Published in:European biophysics journal 2005-06, Vol.34 (4), p.314-322
Main Authors: Aguilella-Arzo, Marcel, Aguilella, Vicente M, Eisenberg, R S
Format: Article
Language:English
Subjects:
Biological Transport
Biophysics - methods
Cell Membrane - metabolism
Computational Biology - methods
Computer Simulation
Diffusion
Electric Conductivity
Electric Impedance
Ion Transport
Ions
Kinetics
Models, Biological
Models, Molecular
Models, Statistical
Poisson Distribution
Salts - pharmacology
Sodium Chloride - pharmacology
Static Electricity
Studies
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Summary:The access resistance (AR) of a channel is an important component of the conductance of ion channels, particularly in wide and short channels, where it accounts for a substantial fraction of the total resistance to the movement of ions. The AR is usually calculated by using a classical and simple expression derived by Hall from electrostatics (J.E. Hall 1975 J. Gen. Phys. 66:531-532), though other expressions, both analytical and numerical, have been proposed. Here we report some numerical results for the AR of a channel obtained by solving the Poisson-Nernst-Planck equations at the entrance of a circular pore. Agreement is found between numerical calculations and analytical results from Hall's equation for uncharged pores in neutral membranes. However, for channels embedded in charged membranes, Hall's expression overestimates the AR, which is much lower and can even be neglected in some cases. The weak dependence of AR on the pore radius for charged membranes at low salt concentration can be exploited to separate the channel and the access contributions to the measured conductance.
ISSN:0175-7571
1432-1017
DOI:10.1007/s00249-004-0452-x