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Multicomponent bilayers
Participating group members: Hao Wang, Fuchang
Yin, Patrick Coppock,
Jennifer Colucci
Biological membranes contain dozens of different types of lipid, a
mixture that is specific to the type of cell and membrane and is
tightly regulated by the cell's metabolic machinery. In learning
about the physical properties of mixed bilayers through computer
simulation, we hope to better understand why this lipid diversity is
so important. We use both atomistic methods and highly simplified
models. The snapshot below is from a Monte Carlo simulation in
which two different lengths of lipid are modeled as simple hard
rods, and the degree of mixing is studied. For more on this model (which was
a research project for two undergraduate students), see
here.
More information can be obtained using molecular models with more realistic representations of molecular structure and interactions.
However, atomistic simulations of lipid mixtures are challenging because lipid lateral diffusion is slow on the practical timescale
for computer simulation, which is generally limited to 10's of nanoseconds for these detailed models. Lipids pretty much stay wherever they
start out for the whole simulation, so it is difficult to learn whether they have a tendency to form clusters or to migrate to different
membrane strutures like transmembrane proteins. Postdoctoral fellow Jason de Joannis
has developed and implemented a method to incorporates "mutation" moves into a simulation, thereby allowing the development of an
equilibrium distribution of lipids orders of magnitude faster than through conventional dynamics simulation.
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