IngentaConnect Monte Carlo Simulation Study of a System with a Dielectric Bounda...

Authors: Boda, Dezső¹; Varga, Tibor¹; Henderson, Douglas²; Busath, David D.³; Nonner, Wolfgang⁴; Gillespie, Dirk⁴; Eisenberg, Bob⁵

Source: Molecular Simulation, Volume 30, Numbers 2-3, February, 2004 , pp. 89-96(8)

Publisher: Taylor and Francis Ltd

Abstract:

Equilibrium Monte Carlo simulations are reported for a model of a biological calcium channel in which the region that includes the channel and the selectivity filter has a different dielectric coefficient than that of the bath. These regions are separated by a sharp dielectric boundary. This simple geometry makes it possible to use the image charge method to incorporate polarization effects. We also include a description of changes in solvation energy that arise when ions move between different dielectrics; we use the Born description of hydration with empirical ionic radii that yield experimental hydration energies. In calculations of Ca<PRE>2+</PRE>vs. Na<PRE>+</PRE> selectivity analogous to those of earlier work (Boda et al., Molec. Phys., 100, 2361 (2002)), we find that reducing the dielectric coefficient in the channel to values as low as 10 renders the channel model less calcium selective. Thus, this continuum description of polarization effects does not capture a delicate balance that seems to exist in biological channels between the energy that ions require for dehydration and the energy that ions gain by interaction with the charged groups in the pore.

Keywords: Polarization effect; Monte Carlo stimulation; Poisson's equation; Biological channel

Document Type: Research article

DOI: 10.1080/0892702031000152226

Affiliations: 1: Department of Physical Chemistry University of Veszprém PO Box 158 H-8201 Veszprém Hungary 2: Department of Chemistry and Biochemistry Brigham Young University 84602-5700 Provo UT USA 3: Department of Physiology and Developmental Biology and Center for Neuroscience Brigham Young University 84602-5700 Provo UT USA 4: Department of Physiology and Biophysics University of Miami School of Medicine 33101 Miami FL USA 5: Department of Molecular Biophysics and Physiology Rush Medical College 60612 Chicago IL USA

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Monte Carlo Simulation Study of a System with a Dielectric Boundary: Application to Calcium Channel Selectivity