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Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
X-ray diffraction structures of some phosphatidylethanolamine lamellar and inverted hexagonal phases
P E Harper1, D A Mannock, R N Lewis
1Department of Physics, Princeton University, Princeton, New Jersey 05844, USA.
Biophysical Journal
|October 19, 2001
Summary
X-ray diffraction reveals how different diacyl phosphatidylethanolamine (PE) structures influence their lamellar and inverted hexagonal phases. These findings detail PE phase behavior and structural dimensions, impacting lipid self-assembly understanding.
Area of Science:
- Biophysics
- Materials Science
Background:
- Diacyl phosphatidylethanolamines (PEs) are crucial membrane lipids.
- Understanding their phase behavior (lamellar L(alpha) and inverted hexagonal H(II)) is key to membrane function.
- Previous studies showed less variation in PE phase dimensions.
Purpose of the Study:
- To determine low-resolution structures of hydrated PE dispersions using X-ray diffraction.
- To analyze the internal dimensions of L(alpha) and H(II) phases as a function of temperature.
- To investigate how PE hydrocarbon chain structure affects phase behavior.
Main Methods:
- X-ray diffraction was employed on aqueous dispersions of seven different diacyl phosphatidylethanolamines (PEs).
- Low-resolution structures of both liquid-crystalline lamellar (L(alpha)) and inverted hexagonal (H(II)) phases were solved.
- Key dimensions including d-spacing, water layer thickness, and headgroup area were measured.
Main Results:
- Significant variations in L(alpha) (51.2–56.4 Å) and H(II) (74.9–82.7 Å) phase d-spacings were observed, dependent on PE chain structure.
- D-spacings decreased with increasing temperature in both phases, with a slower rate in the L(alpha) phase.
- Results contrast with earlier findings of near-constant d-spacings for these PEs.
Conclusions:
- PE hydrocarbon chain structure strongly influences the dimensions of both L(alpha) and H(II) phases.
- Temperature affects d-spacing in both phases, but the rate of change differs.
- A detailed molecular model of the L(alpha)/H(II) phase transition is presented, offering new insights into lipid self-assembly.
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