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Distribution of pentachlorophenol in phospholipid bilayers: a molecular dynamics study
Parag Mukhopadhyay1, Hans J Vogel, D Peter Tieleman
1Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada.
Biophysical Journal
|December 26, 2003
Summary
Molecular dynamics simulations reveal pentachlorophenol (PCP) inserts into lipid bilayers, preferring the acyl chain region. PCP increases lipid chain order and aligns parallel to chains, with its hydroxyl group forming hydrogen bonds at the interface.
Area of Science:
- Biophysics
- Computational Chemistry
- Materials Science
Background:
- Pentachlorophenol (PCP) is a widely used biocide with known environmental persistence.
- Understanding PCP's interaction with biological membranes is crucial for assessing its environmental and toxicological impact.
- Phospholipid bilayers serve as model systems for cell membranes, allowing investigation of xenobiotic interactions.
Purpose of the Study:
- To investigate the molecular distribution and positional preferences of pentachlorophenol (PCP) within phospholipid bilayers.
- To elucidate the effects of PCP on the structural properties of palmitoyl-oleoyl-phosphatidylethanolamine (POPE) and palmitoyl-oleoyl-phosphatidylcholine (POPC) lipid bilayers.
- To explore the molecular mechanisms underlying PCP-lipid interactions, including orientation and hydrogen bonding.
Main Methods:
- Molecular dynamics (MD) computer simulations were employed to model PCP within POPE and POPC lipid bilayers.
- Simulations were initiated from extreme configurations (PCP outside the bilayer) and run for up to 50 nanoseconds (ns).
- Analysis focused on PCP distribution, lipid chain order, lipid tilt angles, dihedral conformations, and hydrogen bond formation.
Main Results:
- PCP preferentially partitions into the hydrophobic core of the lipid bilayer, specifically between carbonyl groups and double bonds in acyl chains.
- The presence of PCP leads to a moderate increase in lipid chain order and a decrease in the average lipid chain tilt angle.
- PCP molecules align parallel to the lipid alkyl chains, optimizing packing within the ordered region of the bilayer.
- The hydroxyl group of PCP engages in hydrogen bonding with both water molecules and lipid oxygen atoms at the bilayer interface.
- The observed increase in lipid chain order was more pronounced in POPC bilayers compared to POPE bilayers.
Conclusions:
- Pentachlorophenol (PCP) integrates into phospholipid bilayers, primarily residing within the acyl chain region and influencing bilayer structure.
- PCP's interaction involves favorable hydrophobic contacts and hydrogen bonding at the interface, leading to increased lipid order.
- These findings provide molecular-level insights into the behavior of PCP in membrane-like environments, relevant for environmental and toxicological studies.