Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 23, 2018 - November 25, 2018
Cholesterol molecule is abundant in phospholipid bilayers of animal cell membranes and is known to prevent rupture of the bilayer under mechanical stretching. Recent molecular dynamics simulation studies showed that the mechanical stretching induces the phase transition to the interdigitated phase in the phospholipid/cholesterol bilayer and also showed that the interdigitated bilayer could withstand larger areal strain without rupturing than non-interdigitated bilayer. However, the molecular-level reason why the interdigitated bilayer is hard to rupture is still unclear. The bilayer rupture by stretching is initiated by the permeation of water molecules into the bilayer inside. Thus, to clarify the effects of the interdigitation on the initiation of the bilayer rupture, the water permeation through the bilayer, we performed a series of molecular dynamics simulations of the stretched phospholipid/cholesterol bilayers. To evaluate the water permeability change, we calculated the potential of mean force (PMF) of the water molecule in the bilayer. PMF means an energetic barrier for the water permeation and is a dominant factor for determining the water permeability. We found that the maximum height of the PMF for the interdigitated bilayer is larger than those for non-interdigitated bilayers. This implies that the phase transition to the interdigitated phase impedes the water permeation and might also impede the subsequent bilayer rupture. We suspect that the decrease in the water permeability with the stretch-induced phase transition might be a molecular-level reason why the cholesterol-containing bilayer is hard to rupture under stretching.
