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Anomalous phase behavior of long chain saturated lecithin bilayers
W J Sun1, S Tristram-Nagle, R M Suter
1Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Biochimica Et Biophysica Acta
|February 21, 1996
Summary
Longer chain lecithins exhibit unique behavior in ordered phases. A second gel phase (G2) with reversed symmetry and hexagonal chain packing was observed in hydrated multilamellar vesicles.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Lecithins are key components of biological membranes.
- Understanding lecithin phase behavior is crucial for membrane biophysics.
- Lipid chain length significantly influences phase transitions and properties.
Purpose of the Study:
- To investigate the effect of long lecithin chain lengths on phase behavior.
- To characterize the ordered phases of hydrated multilamellar vesicles.
- To identify and describe novel gel phases in lecithins.
Main Methods:
- X-ray scattering was employed to study hydrated, unoriented multilamellar vesicles.
- Experiments were conducted across a range of temperatures.
- Focus was placed on lecithins with even chain lengths, particularly n=24.
Main Results:
- Lecithins with longer chain lengths (n ≥ 20) displayed anomalous behavior compared to shorter chains.
- A distinct second gel phase (G2) was identified below 40°C for n=24.
- The G2 phase exhibits a small tilt angle and reversed hexagonal symmetry breaking.
- Above 45°C, hexagonal chain packing with a small chain tilt angle was suggested.
Conclusions:
- Lecithin chain length is a critical determinant of phase behavior.
- A novel G2 gel phase with unique structural characteristics exists in long-chain lecithins.
- X-ray scattering reveals complex phase transitions in hydrated lipid systems.