74
Modeling of Biomolecular Systems Interactions, Dynamics, and Allostery Poster Session I
21-POS
Board 21
Prediction of Hydrophobe Extrusion Out of Bilayer
Vitaly Chaban
, Himanshu Khandelia.
Memphys, SDU, Odense , Denmark.
The biological membranes can swallow a large variety of hydrophobic molecules floating nearby
in vivo. Many of these molecules exhibit a limited solubility in the phospholipid bilayers.
Therefore, separate phases can emerge between the leaflets. As new molecules join the
encapsulated phase, its size finally exceeds certain limit (specific for each bilayer composition)
and the separation takes place. Depending on the affinity between the phospholipids and the
hydrophobe particles, the confined phase can be a droplet (in case of low attraction), a disc in
case of stronger attraction) or can be distributed throughout the bilayer plane (in case of
significant solubility).
We introduce a method to predict the critical linear sizes of encapsulated hydrophobic phase,
which trigger curvature-driven extrusion. The phase extrudes when the projected force of its
repulsion from the bilayer exceeds the force of phospholipids attraction within the bilayer. The
larger is the curvature of the phase, the larger force (repulsive energy) it generates in the system.
One can consider a range of relatively small (spatially) phases inside the bilayer and record the
force corresponding to the bilayer resistance. The obtained function of penalty force versus phase
volume must be extrapolated to zero force. Zero force, by definition, corresponds to a free
motion of an object, i.e. spontaneous separation of two phases.
The proposed method can be applied to a variety of lipid bilayers and various encapsulated
hydrophobes to get information about their separation and the durability of the bilayer curvature.
The method allows the investigation of length scales, which are inaccessible for direct computer
simulations with an explicit molecular resolution
