Synthetic nanopores with fixed charges: an electrodiffusion model for ionic transport.

Synthetic nanopores with fixed charges exhibit ionic equilibrium and transport properties that resemble those displayed by biological ion channels. We present an electrodiffusion model based on the Nernst-Planck flux equations, which allows for a qualitative description of the steady state ionic transport through a nanopore when the membrane fixed charges and all mobile carriers (including the water ions) are properly taken into account. In particular, we study the current-voltage curve, the electrical conductance, the reversal potential (a measure of the nanopore ionic selectivity), as well as the flux inhibition by protons and divalent cations in the nanopore. The model clearly shows how the changes in the ionization state of the fixed charges with pH and salt concentration dictate the electrical properties of the nanopore. The agreement between the model predictions and previous experimental data allows us to identify which are the main characteristics that permit a simple description of this complex system.

[1]  Serdar Kuyucak,et al.  Invalidity of continuum theories of electrolytes in nanopores , 2000 .

[2]  V. Aguilella,et al.  Ionic Transport Across Porous Charged Membranes and the Goldman Constant Field Assumption , 1986 .

[3]  D. Levitt,et al.  Modeling of Ion Channels , 1999, The Journal of general physiology.

[4]  B. Eisenberg,et al.  Anomalous mole fraction effect, electrostatics, and binding in ionic channels. , 1998, Biophysical journal.

[5]  B. Eisenberg,et al.  Progress and Prospects in Permeation , 1999, The Journal of general physiology.

[6]  J. Manzanares,et al.  Ion-exchange fibers and drugs: an equilibrium study. , 2001, Journal of controlled release : official journal of the Controlled Release Society.

[7]  A. Nitzan,et al.  A lattice relaxation algorithm for three-dimensional Poisson-Nernst-Planck theory with application to ion transport through the gramicidin A channel. , 1999, Biophysical journal.

[8]  A. Alcaraz,et al.  pH and supporting electrolyte concentration effects on the passive transport of cationic and anionic drugs through fixed charge membranes , 1999 .

[9]  D. Baur,et al.  Rectification and voltage gating of ion currents in a nanofabricated pore , 2002 .

[10]  J. Schlenoff,et al.  “Internal pKa's” in Polyelectrolyte Multilayers: Coupling Protons and Salt , 2002 .

[11]  Reinhard Neumann,et al.  Electro-responsive asymmetric nanopores in polyimide with stable ion-current signal , 2003 .

[12]  Modulation of surface flow by divalent cations and protons , 1993 .

[13]  Reimar Spohr,et al.  Diode-like single-ion track membrane prepared by electro-stopping , 2001 .

[14]  M Forte,et al.  Large scale rearrangement of protein domains is associated with voltage gating of the VDAC channel. , 1992, Biophysical journal.

[15]  S. Bezrukov,et al.  Alamethicin channel conductance modified by lipid charge , 2001, European Biophysics Journal.

[16]  C. Pasternak,et al.  Fluctuation of surface charge in membrane pores. , 2002, Biophysical journal.

[17]  M. Colombini,et al.  The voltage-gating process of the voltage-dependent anion channel is sensitive to ion flow. , 1998, Biophysical journal.

[18]  Z. Siwy,et al.  Fabrication of a synthetic nanopore ion pump. , 2002, Physical review letters.

[19]  A. Alcaraz,et al.  Model calculations of ion transport against its concentration gradient when the driving force is a pH difference across a charged membrane , 1997 .

[20]  A. Alcaraz,et al.  Modeling of Amino Acid Electrodiffusion through Fixed Charge Membranes , 2001 .

[21]  B. Eisenberg,et al.  Ion permeation and glutamate residues linked by Poisson-Nernst-Planck theory in L-type calcium channels. , 1998, Biophysical journal.

[22]  R. Eisenberg,et al.  Modified Donnan potentials for ion transport through biological ion channels. , 2001, Physical review. E, Statistical, nonlinear, and soft matter physics.

[23]  Y. Korchev,et al.  Rapid switching of ion current in narrow pores: implications for biological ion channels , 1993, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[24]  Pieter Stroeve,et al.  Self-Assembled Monolayers on Electroless Gold Impart pH-Responsive Transport of Ions in Porous Membranes , 2000 .

[25]  D. Shah,et al.  Effect of degree, type, and position of unsaturation on the pKa of long-chain fatty acids. , 2002, Journal of colloid and interface science.