Mechanism of Ion Permeation in a Model Channel: Free Energy Surface and Dynamics of K+ Ion Transport in an Anion-Doped Carbon Nanotube
| Autor: | Shinji Saito, Takashi Sumikama, Iwao Ohmine |
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| Rok vydání: | 2006 |
| Předmět: |
Anions
Nanotube Cell Membrane Permeability Biophysics Molecular Conformation Analytical chemistry Carbon nanotube Models Biological Ion Channels law.invention Ion Diffusion law Materials Chemistry Molecule Physical and Theoretical Chemistry Ion transporter Ions Ion Transport Models Statistical Toy model Chemistry Physical Nanotubes Carbon Chemistry Water Models Theoretical Permeation Surfaces Coatings and Films Chemical physics Potassium Thermodynamics Communication channel |
| Zdroj: | The Journal of Physical Chemistry B. 110:20671-20677 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp062547r |
| Popis: | The mechanism of the ion permeation is investigated for an anion-doped carbon nanotube, as a model of the K+ channel, by analyzing the free energy surface and the dynamics of the ion permeation through the model channel. It is found that the main rate-determining step is how an ion enters the channel. The entrance of the ion is mostly blocked by a water molecule located at this entrance. Only about 10% of K+ ions which reach the mouth of the channel can really enter the channel. The rejection rate sensitively depends on the location of this water molecule, which is easily controlled by the charge of the carbon nanotube; for example, the maximum permeation is obtained when the anion charge is at a certain value, -5.4e in the present model. At this charge, the facile translocation of the ion inside the channel is also induced due to the number of fluctuations of the ions inside the channel. Therefore, the so-called "Newton's balls", a toy model, combined with a simple ion diffusion model for explaining the fast ion permeation should be modified. The present analysis thus suggests that there exists an optimum combination of the length and the charge of the carbon nanotube for the most efficient ion permeation. |
| Databáze: | OpenAIRE |
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