Molecular
Structures of Fluid Phosphatidylethanolamine
Bilayers Obtained
from Simulation-to-Experiment Comparisons and Experimental Scattering
Density Profiles
Following our previous efforts in
determining the structures of
commonly used PC, PG, and PS bilayers, we continue our studies of
fully hydrated, fluid phase PE bilayers. The newly designed parsing
scheme for PE bilayers was based on extensive MD simulations, and
is utilized in the SDP analysis of both X-ray and neutron (contrast
varied) scattering measurements. Obtained experimental scattering
form factors are directly compared to our simulation results, and
can serve as a benchmark for future developed force fields. Among
the evaluated structural parameters, namely, area per lipid <i>A</i>, overall bilayer thickness <i>D</i><sub>B</sub>, and hydrocarbon region thickness 2<i>D</i><sub>C</sub>, the PE bilayer response to changing temperature is similar to previously
studied bilayers with different headgroups. On the other hand, the
reduced hydration of PE headgroups, as well as the strong hydrogen
bonding between PE headgroups, dramatically affects lateral packing
within the bilayer. Despite sharing the same glycerol backbone, a
markedly smaller area per lipid distinguishes PE from other bilayers
(i.e., PC, PG, and PS) studied to date. Overall, our data are consistent
with the notion that lipid headgroups govern bilayer packing, while
hydrocarbon chains dominate the bilayer’s response to temperature
changes