Nano Science and Technology InstituteNano Science and Technology Institute
Nano Science and Technology Institute 2004 NSTI Nanotechnology Conference & Trade Show
Nanotech 2004
BioNano 2004
Topics & Tracks
Index of Authors
Business & Investment
2004 Sub Sections
Venue 2004
Press Room
Purchase CD/Proceedings
NSTI Events
Site Map
Nanotech Proceedings
Nanotechnology Proceedings
Supporting Organizations
Nanotech Supporting Organizations
Media Sponsors
Nanotech Media Sponsors
Event Contact
696 San Ramon Valley Blvd., Ste. 423
Danville, CA 94526
Ph: (925) 353-5004
Fx: (925) 886-8461

Selectivity: How Biological Ion Channels Distinguish Among Different Ion Species

D. Gillespie, W. Nonner and R.S. Eisenberg
Rush University Medical Center, US

Keywords: ion channels, selectivity, excluded volume, electrostatics

Biological ion channels conduct ions (mainly Na+, K+, Ca2+, and Cl-) across membranes that are otherwise impermeable to charged particles. Following their chemical potential gradients, ions flow through the pore of a channel using much of the same physics as electrons and holes in semiconductors; the very successful Poisson-Nernst-Planck (PNP) model of ion conduction used the same Poisson/drift-diffusion equations used in semiconductor modeling. Although the current/voltage curves of different classes of ion channel show as much variation as the different classes of semiconductors, channels have some very unique properties due to evolutionary pressure and the availability of different charge carriers. Specifically, different ion channel classes have evolved to conduct specific ions, a characteristic called selectivity. By adding a model of the finite size of ions (ions are not point charges) to the Poisson/drift-diffusion equations, the physical mechanism of how ion channels distinguish among different ion species (e.g., between Na+ and K+) is becoming understood. Using the examples of Ca2+, Na+, and Cl- selective channels, selectivity is shown to be an interplay of electrostatics and excluded volume (two ions cannot occupy the same space). Because the structures of the various channel types are distinctly different, the weight given to each component (electrostatic or excluded volume) is varied, leading to very different selectivity properties among channels: the Ca2+ channel prefers Ca2+ over Na+ while the opposite is true for the Na+ channel; both of these channels prefer small ions, while the Cl- channel prefers large ions.

Nanotech 2004 Conference Technical Program Abstract

Nanotech Sponsors
News Headlines
NSTI Online Community

© Nano Science and Technology Institute, all rights reserved.
Terms of use | Privacy policy | Contact