| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Boda * 
* Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois; Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, Florida; Department of Physical Chemistry, University of Pannonia, Veszprém, Hungary; and Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah
Correspondence: Address reprint requests to R. S. Eisenberg, Tel.: 312-942-6467; E-mail: beisenbe{at}rush.edu.
Monte Carlo simulations of equilibrium selectivity of Na channels with a DEKA locus are performed over a range of radius R and protein dielectric coefficient 
p. Selectivity arises from the balance of electrostatic forces and steric repulsion by excluded volume of ions and side chains of the channel protein in the highly concentrated and charged (
30 M) selectivity filter resembling an ionic liquid. Ions and structural side chains are described as mobile charged hard spheres that assume positions of minimal free energy. Water is a dielectric continuum. Size selectivity (ratio of Na+ occupancy to K+ occupancy) and charge selectivity (Na+ to Ca2+) are computed in concentrations as low as 10–5 M Ca2+. In general, small R reduces ion occupancy and favors Na+ over K+ because of steric repulsion. Small p increases occupancy and favors Na+ over Ca2+ because protein polarization amplifies the pore's net charge. Size selectivity depends on R and is independent of p; charge selectivity depends on both R and p. Thus, small R and p make an efficient Na channel that excludes K+ and Ca2+ while maximizing Na+ occupancy. Selectivity properties depend on interactions that cannot be described by qualitative or verbal models or by quantitative models with a fixed free energy landscape.
This article has been cited by other articles:
 |
|
 |
|
  D. Gillespie and M. Fill Intracellular Calcium Release Channels Mediate Their Own Countercurrent: The Ryanodine Receptor Case Study Biophys. J., October 15, 2008; 95(8): 3706 - 3714. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Gillespie and D. Boda The Anomalous Mole Fraction Effect in Calcium Channels: A Measure of Preferential Selectivity Biophys. J., September 15, 2008; 95(6): 2658 - 2672. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Vora, D. Bisset, and S.-H. Chung Conduction of Na+ and K+ through the NaK Channel: Molecular and Brownian Dynamics Studies Biophys. J., August 15, 2008; 95(4): 1600 - 1611. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Gillespie, D. Boda, Y. He, P. Apel, and Z. S. Siwy Synthetic Nanopores as a Test Case for Ion Channel Theories: The Anomalous Mole Fraction Effect without Single Filing Biophys. J., July 15, 2008; 95(2): 609 - 619. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. M. Lipkind and H. A. Fozzard Voltage-gated Na Channel Selectivity: The Role of the Conserved Domain III Lysine Residue J. Gen. Physiol., June 1, 2008; 131(6): 523 - 529. [Full Text] [PDF]
|
|
|
|
|
|
R. Roth, D. Gillespie, W. Nonner, and R. E. Eisenberg Bubbles, Gating, and Anesthetics in Ion Channels Biophys. J., June 1, 2008; 94(11): 4282 - 4298. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Boda, W. Nonner, D. Henderson, B. Eisenberg, and D. Gillespie Volume Exclusion in Calcium Selective Channels Biophys. J., May 1, 2008; 94(9): 3486 - 3496. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B. Eisenberg Engineering channels: Atomic biology PNAS, April 29, 2008; 105(17): 6211 - 6212. [Full Text] [PDF]
|
|
|
|
|
|
D. Gillespie Energetics of Divalent Selectivity in a Calcium Channel: The Ryanodine Receptor Case Study Biophys. J., February 15, 2008; 94(4): 1169 - 1184. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
