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Membrane-contaminant interaction found by 3D force field calculations.
H A J Govers1, P De Voogt, O Kwast
1Department of Environmental and Toxicological Chemistry, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, The Netherlands. hgovers@science.uva.nl
SAR and QSAR in Environmental Research
|June 21, 2002
Summary
This study calculated contaminant transfer enthalpies to lipid membranes, assessing 3D force fields for predicting bio-concentration. Results show varying contaminant affinities for membrane sites, with some aligning well with experimental data.
Area of Science:
- Computational chemistry
- Environmental science
- Biophysics
Background:
- Understanding contaminant partitioning into biological membranes is crucial for predicting bio-concentration.
- Accurate computational models are needed to assess contaminant interactions with lipid bilayers.
Purpose of the Study:
- To evaluate 3D force fields for calculating membrane-water partitioning constants (Kmw).
- To explore the use of calculated enthalpies of transfer as descriptors for bio-concentration.
- To investigate contaminant interactions within a 1,2-Dilauroyl-DL-phosphatidyl ethanolamine (DLPE) membrane model.
Main Methods:
- A 3D DLPE membrane model was constructed using the MM+ force field and AM1 atomic charges.
- Interaction energies of contaminants (PCB14, PCB15, PPDDT, atrazine) with membrane sites were calculated via geometrical optimization.
- Hydration energies were subtracted from membrane-contaminant interaction energies to determine transfer enthalpies.
Main Results:
- Enthalpies of transfer from water to the DLPE membrane were calculated: PCB14 (4.7 kcal/mol), PCB15 (-2.3 kcal/mol), PPDDT (11.5 kcal/mol), and atrazine (-9.2 kcal/mol).
- PCB14 results showed good agreement with experimental data for similar membranes.
- PCB14, PCB15, and PPDDT favored apolar membrane sites, while atrazine localized at the polar membrane-bulk water boundary.
Conclusions:
- 3D force fields show potential for calculating Kmw and bio-concentration descriptors.
- Contaminant partitioning behavior varies significantly based on chemical structure and membrane site polarity.
- The computational approach offers insights into contaminant-membrane interactions, with discussed advantages and limitations.