An extensive simulation study of lipid bilayer properties with different head groups, acyl chain lengths, and chain saturations.
Previous MD simulations of six phosphocholine (PC) lipid bilayers demonstrated the accuracy of the CHARMM36 force field (C36FF) for PC bilayer simulation at varied temperatures (BBA-Biomembranes, 1838 (2014): 2520-2529). In this work, we further examine the accuracy of C36FF over a wide temperature range for a broader range of lipid types such as various head groups (phosphatidic acid (PA), PC, phosphoethanolamine (PE), phosphoglycerol (PG), and phosphoserine (PS)), and tails (saturated, mono-, mixed- and poly-unsaturated acyl chains with varied chain lengths). The structural properties (surface area per lipid (SA/lip), overall bilayer thickness, hydrophobic thickness, headgroup-to-headgroup thickness, deuterium order parameter (SCD), and spin-lattice relaxation time (T1)) obtained from simulations agree well with nearly all available experimental data. Our analyses indicate that PS lipids have the most inter-lipid hydrogen bonds, while PG lipids have the most intra-lipid hydrogen bonds, which play the main role in their low SA/lip in PS lipids and low thicknesses in PG lipids, respectively. PS, PE, and PA lipids have the largest contact clusters with on average 5-8 lipids per cluster, while PC and PG have clusters of 4 lipids based on a cutoff distance of 6.5Å. PS lipids have much slower lipid wobble (i.e., higher correlation time) than other head groups at a given temperature as the hydrogen bonded network significantly reduces a lipid's mobility, and the rate of lipid wobble increases dramatically as temperature increases. These in-depth analyses facilitate further understanding of lipid bilayers at the atomic level.
Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA.
Xiaohong
X
Zhuang
Department of Molecular Biosciences, The University of Kansas, Lawrence, KS 66047, USA.
Eder M
EM
Dávila-Contreras
Department of Chemistry, The University of Kansas, Lawrence, KS 66047, USA.
Andrew H
AH
Beaven
Department of Biological Sciences and Bioengineering Program, Lehigh University, Bethlehem, 18015, USA. Electronic address: wonpil@lehigh.edu.
Wonpil
W
Im
Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742, USA; Biophysics Program, University of Maryland, College Park, MD 20742, USA. Electronic address: jbklauda@umd.edu.
Jeffery B
JB
Klauda
D003903:Deuterium; D020404:Glycerophospholipids / Q000737:chemistry; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D013696:Temperature
D020404:Glycerophospholipids; D008051:Lipid Bilayers; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D003903:Deuterium
Force field accuracy; Lipid wobble; Molecular dynamics; Structural property