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Membrane builder
A special
protocol was developed to assemble the starting configuration
for MD simulations of membrane proteins associated with phospholipid
bilayer membranes. The purpose of the protocol is to construct
an initial configuration of a protein-membrane complex that
is as close as possible to that of an equilibrated system.
The construction method was developed by Woolf and Roux and
applied to the simulation of the gramicidin A channel, pf1
coat protein, melittin and the KcsA potassium channel (Woolf
and Roux, 1994; Woolf and Roux, 1996, Berneche et al., 1998;
Berneche and Roux, 2000). This approach represents an extension
of the work of Pastor and co-workers to investigate pure lipid
bilayers (Pastor et al., 1991; Venable et al., 1993).
Our general
strategy for creating a reasonable starting configuration
for the protein phospholipid system consists in randomly selecting
lipids from a pre-equilibrated and pre-hydrated set, placing
them around the protein, and finally reducing the number of
core-core overleaps between heavy atoms through systematic
rotations (around the Z-axis) and translations (in the XY
plane) of the lipids and protein. To provide the initial XY
positions for each lipid, the full molecules are first represented
as single effective particles corresponding to the average
cross-section area of a single phospholipid. The packing of
the effective lipid particles around the protein is determined
from a MD simulation in which the large effective particles
are harmonicaly restrained at a given value of Z and moving
in the XY plane with periodic boundary conditions.
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