Structural Change in Lipid Bilayer and Water Penetration Induced by Shock Wave: Molecular Dynamics Simulations
Ken-ichiro Koshiyama 1, Tetsuya Kodama 2, Takeru Yano 1 and Shigeo Fujikawa 1*
1 Division of Mechanical and Space Engineering, Hokkaido University
2 Biomedical Engineering Research Organization, Tohoku University
* To whom correspondence should be addressed. E-mail: fujikawa{at}eng.hokudai.ac.jp.
Submitted on January 18, 2006
Revised on February 19, 2006
Accepted on 13 June 2006
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Abstract |
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The structural change of a phospholipid bilayer in water under the action of a shock wave is numerically studied with unsteady nonequilibrium molecular dynamics (MD) simulations. The action of shock wave is modeled by the momentum change of water molecules, and thereby we demonstrate that the resulting collapse and rebound of the bilayer are followed by the penetration of water molecules into the hydrophobic region of the bilayer. The high-speed phenomenon that occurs during the collapse and rebound of the bilayer is analyzed in detail, particularly focusing on the change of bilayer thickness, the acyl chain bend angles, the lateral fluidity of lipid molecules, and the penetration rate of water molecules. The result shows that the high-speed phenomenon can be divided into two stages; in the first stage the thickness of bilayer and the order parameter are rapidly reduced, and then in the second stage they are recovered relatively slowly. It is in the second stage that water molecules are steadily introduced into the hydrophobic region. The penetration of water molecules is enhanced by the shock wave impulse and this qualitatively agrees with a recent experimental result.
Key Words:
biomolecular dynamics, penetration rate of water molecules, phospholipid bilayer, shock wave impulse, sonoporation, unsteady nonequilibrium simulations
