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Date: Fri, 24 Nov 95 14:20:45 +0100
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To: toukie %-% at %-% zui.unizh.ch
From: vkitzing*- at -*sunny.mpimf-heidelberg.mpg.de (Eberhard von Kitzing)
Subject: Re: CCL:Two questions
Cc: CHEMISTRY /at\www.ccl.net (Computational Chemistry List)


Dear Prof. Shapiro,

>    (ii) Does anyone have any information on experimental (preferred)
>         or theoretical (OK) values for the dielectric constant in
>         the interior of lipid bilayers, artificial membranes, or
>         (preferred) biological membranes?

There is no simple answer to this question. In the experimental as well as
in the theoretical case the answer depends on what property you are
concentrating.

Membranes, especially biological ones, are highly inhomogeneous. Thismeans
that the local dielectric constant does vary from place to place (perhaps
in the range between 2.5 for hydrocarbones to 6 for more polarizable
materials).

The situation get more complicated if you consider the effective dielectric
constant, a measure of the screening of two charges due to the presence of
the dielectric properties of water and the membrane. In this case, the
value cannot be lower than the membrane dielectric constant but can become
large than the water dielectric constant. 

This problem has been considered for estimating the energy barriers for
ions permeating through ion channels. For this problem there exists a huge
amount of literature (see below). In these studies, however, the effect of
the electrolyte has often been neglected. Counter ions always increase the
charge-charge screening.

%0 Journal Article
%A Parsegian, V. Adrian
%D 1969
%T Energy of an Ion crossing a Low Dielectric Membrane: Solutions to Four
Relevant Electrostatic Problems
%J Nature
%V 221
%P 844-846
%K continuum theory, dielectric constant, membrane, ion channels, ion
carriers, mirror image, image charge, image force
%X The influences on ion energy of membrane thickness, ion-pair formation,
pores, and carriers have been estimated. Only pores and carriers lower the
energy barrier significantly


%0 Journal Article
%A Parsegian, V. Adrian
%D 1975
%T Ion-Membrane interactions a structural forces
%J Annals of the New York Academy of Sciences
%V 264
%P 161-174
%K continuum theory, dielectric constant, membrane, ion channels, ion
carriers, mirror image, image charge, image force


%0 Book Section
%A Jordan, Peter C.
%D 1993
%T Interactions of ions with membrane proteins
%B Thermodynamics of Membrane Receptors and Channels
%E Jackson, Meyer B.
%I CRC Press
%C Boca Raton
%P 27-80
%K continuum model, effective dielectric constant, Born energy, Eyring
theory, Nernst-Planck equation, energy profiles, gramicidine, ionic
strength effects, conductivity, alamethicin, acetylcholin receptor channel,
voltage gated channels, anion channels


%0 Journal Article
%A Partenskii, Michael B.
%A Dorman, Vladimir
%A Jordan, Peter C.
%D 1994
%T Influence of a channel-forming peptide on energy barriers to ion
permeation, viewed from a continuum dielectric perspective
%J Biophysical Journal
%V 67
%N 4
%P 1429-1438
%K ** gramicidin channel; dynamics; water; model; electrostatics;
simulations; movement; constant; membrane electrostatic barrier;
electrostatic screening; ion transport; ionic conductivity; dielectric
screening


%0 Journal Article
%A Zhou, F.
%A Schulten, K.
%D 1995
%T Molecular-dynamics study of a membrane water interface
%J Journal of Physical Chemistry
%V 99
%N 7
%P 2194-2207
%F Review
%K ** lipid bilayer-membranes; hydration forces; phospholipid-bilayers;
computer-simulation; dilauroylphosphatidylethanolamine bilayers;
electrostatic interactions; amphiphilic surfaces; dielectric-constant;
boundary-conditions; magnetic-resonance;


-------------------------------------------------------------------------

Eberhard von Kitzing
Max-Planck-Institut fuer Medizinische Forschung
Jahnstr. 29, D69120 Heidelberg, FRG

Carl-Zuckmayer Str. 17, D69126 Heidelberg (privat)

FAX : +49-6221-486 459  (work)
Tel.: +49-6221-486 467  (work)
Tel.: +49-6221-385 129  (home)

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