Simulating POPC and POPC/POPG Bilayers: Conserved Packing and Altered Surface Reactivity
Lorant Janosi1, Alemayehu A Gorfe1
1Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, MSB 4.108, Houston, Texas 77030.
Journal of Chemical Theory and Computation
|December 1, 2015
Summary
Molecular dynamics simulations reveal that mixed bilayers of neutral and charged lipids exhibit similar overall properties to pure bilayers. However, charged lipids form hydrogen bonds with neutral lipids, altering water molecule ordering near the headgroup.
Area of Science:
- Biophysics
- Computational Chemistry
- Materials Science
Background:
- Molecular dynamics (MD) simulations are crucial for studying bilayer properties.
- Application of MD to mixed lipid bilayers, especially those with charged components, remains less explored.
Purpose of the Study:
- Investigate the structural and dynamic properties of mixed bilayers containing neutral and charged lipids using MD simulations.
- Compare the behavior of mixed bilayers with pure bilayers to understand the impact of charged lipids.
Main Methods:
- Performed constant temperature and pressure MD simulations.
- Utilized the updated CHARMM force field for simulations.
- Simulated mixed bilayers of 2-oleoyl-1-pamlitoyl-sn-glyecro-3-phosphocholine (POPC) and 2-oleoyl-1-pamlitoyl-sn-glyecro-3-glycerol (POPG) (23% POPG).
- Included a control simulation of a pure POPC bilayer.
Main Results:
- Equilibrium properties of the mixed bilayer were comparable to the pure POPC bilayer.
- Nearly 50% of POPG lipids engaged in hydrogen bonding with POPC lipids.
- Mixed bilayers showed altered water molecule ordering compared to pure POPC bilayers, particularly at longer distances.
- Differences between mixed and pure bilayers were localized to the headgroup region.
Conclusions:
- Mixed phospholipid bilayers with approximately 23% negative charge content exhibit subtle yet significant differences from neutral bilayers.
- Hydrogen bonding between charged and neutral lipids and altered water hydration are key distinctions at the headgroup level.
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