BIOPHYSICAL THEORY AND MODELING |
A Hybrid Model for Erythrocyte Membrane: A Single Unit of Protein Network Coupled with Lipid Bilayer
Qiang Zhu 1, Carlos J. Vera 2, Robert J. Asaro 1, Paul Sche 2 and L. Amy Sung 2*
1 UCSD, Department of Structural Engineering
2 UCSD, Department of Bioengineering
* To whom correspondence should be addressed. E-mail: amysung{at}bioeng.ucsd.edu.
Submitted on August 1, 2006
Revised on October 26, 2006
Accepted on 13 March 2007
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Abstract |
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To investigate the nano-mechanics of the erythrocyte membrane we have developed a hybrid model that couples the actin-spectrin network to the lipid bilayer. This model features a Fourier-Space-Brownian-Dynamics model of the bilayer, a Brownian-Dynamics model of the actin protofilament, and a modified WLC model of the spectrin (including a cable-dynamics model to predict the oscillation in tension). This model enables us to predict the nano-mechanics of single or multiple units of the protein network, the lipid bilayer, and the effect of their interactions. The present work is focused on the attitude of the actin protofilament at the equilibrium states coupled with the elevations of the lipid bilayer through their primary linkage at the suspension complex in deformations. Two different actin-spectrin junctions are considered at the junctional complex. With a point-attachment junction, large pitch angles and bifurcation of yaw angles are predicted. Thermal fluctuations at bifurcation may lead to mode-switching, which may affect the network and the physiological performance of the membrane. In contrast, with a wrap-around junction pitch angles remain small, and the occurrence of bifurcation is greatly reduced. These simulations suggest the importance of 3-D molecular junctions and the lipid bilayer/protein network coupling on cell membrane mechanics.
Key Words:
junctional complex, nanomechanics, skeleton-bilayer interaction, thermal fluctuation, three-dimensional model, wrap-around juction
