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Volumetric stability of lipid bilayers
Kelsey M Hallinen1, Stephanie Tristram-Nagle, John F Nagle
1Biological Physics Group, Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Physical Chemistry Chemical Physics : PCCP
|October 17, 2012
Summary
Repeated heating and cooling of dipalmitoylphosphatidylcholine (DPPC) lipid bilayers caused an apparent volume decrease, but this was found to be an artifact. Gel phase DPPC bilayers are volumetrically stable, with no significant changes in lipid volume.
Area of Science:
- Biophysical Chemistry
- Materials Science
- Membrane Biophysics
Background:
- Dipalmitoylphosphatidylcholine (DPPC) is a key phospholipid in biological membranes.
- Understanding lipid volume stability is crucial for biomembrane physical chemistry.
- Previous reports suggested a decrease in DPPC lipid volume upon thermal cycling.
Purpose of the Study:
- To investigate the volumetric stability of DPPC lipid bilayers in the gel phase.
- To determine if repeated thermal cycling affects lipid molecular volume.
- To clarify discrepancies in previous findings regarding DPPC volume changes.
Main Methods:
- Commercial densimetry was used to measure DPPC multilamellar vesicle dispersions.
- Neutral buoyancy measurements were performed on similar dispersions.
- Thermal cycling was conducted between 10 °C and 50 °C.
- Lipid remixing experiments were conducted to identify artifacts.
Main Results:
- Densimetry indicated a gradual decrease in DPPC lipid molecular volume upon repeated thermal cycling.
- Neutral buoyancy measurements showed no gradual change in DPPC lipid volume.
- Remixing experiments revealed the apparent volume decrease observed in densimetry to be an artifact.
- Gel phase DPPC bilayers were found to be volumetrically stable.
Conclusions:
- The apparent decrease in DPPC lipid molecular volume is an artifact of the densimetry method.
- Gel phase DPPC bilayers exhibit volumetric stability under repeated thermal cycling.
- Biomembrane physical chemistry is not significantly impacted by volume changes in DPPC under these conditions.
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