Modeling of Biomolecular Systems Interactions, Dynamics, and Allostery: Bridging Experiments and Computations - September 10-14, 2014, Istanbul, Turkey

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

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