Calculating the bulk modulus for a lipid bilayer with nonequilibrium molecular dynamics simulation.
Nonequilibrium molecular dynamics (NEMD) computer simulations are used to calculated the bulk modulus for a dimyristoylphosphatidylcholine bilayer. A methodology is developed whereby NEMD can be effectively used to calculate material properties for complex systems that undergo long time-scale conformational changes. It is found that the bulk modulus upon expansion from a zero stress state agrees well with experimental estimates. However, it is also found that the modulus upon contraction from a zero stress state is larger. From a molecular perspective, it is possible to explain this phenomena by examining the molecular origins of the pressure response. The finding that the two moduli are not equal upon compression and expansion is in apparent contradiction to osmotic stress experiments where the area modulus was found to be the same upon expansion and contraction. This issue is addressed.
Ayton
Gary
G
Department of Chemistry and Henry Eyring Center for Theoretical Chemistry, University of Utah, Salt Lake City, Utah, 84112 USA.
Smondyrev
Alexander M
AM
Bardenhagen
Scott G
SG
McMurtry
Patrick
P
Voth
Gregory A
GA
D000465:Algorithms; D003198:Computer Simulation; D008051:Lipid Bilayers / Q000737:chemistry*; D009995:Osmosis; D011487:Protein Conformation; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D008051:Lipid Bilayers; D014867:Water