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Location of two antioxidants in oriented model membranes. Small-angle x-ray diffraction study.
J Katsaras1, R H Stinson, J H Davis
1Department of Physics, University of Guelph, Ontario, Canada.
Biophysical Journal
|March 1, 1991
Summary
Small-angle X-ray diffraction located butylated hydroxytoluene (BHT) in lipid bilayers, while delta-tocopherol was found near the headgroup region. Bromination confirmed these distinct molecular positions.
Area of Science:
- Biophysics
- Materials Science
- Structural Biology
Background:
- Lipid bilayers are fundamental to cell membranes.
- Antioxidants like butylated hydroxytoluene (BHT) and delta-tocopherol play crucial roles in biological systems.
- Understanding the precise location of these molecules within lipid bilayers is essential for elucidating their function.
Purpose of the Study:
- To determine the location of butylated hydroxytoluene (BHT) and delta-tocopherol within dipalmitoylphosphatidylcholine (DPPC) lipid bilayers, with and without cholesterol.
- To investigate the influence of cholesterol on the molecular arrangement of these compounds.
- To validate molecular positioning using brominated analogues and advanced diffraction analysis.
Main Methods:
- Small-angle X-ray diffraction (SAXD) was employed to analyze oriented DPPC and DPPC-cholesterol bilayers containing 40 mol% BHT or delta-tocopherol.
- Phase determination was achieved through swelling experiments and analysis of structure factors in reciprocal space.
- Fourier synthesis and difference Patterson maps were utilized to generate electron density profiles and confirm atomic positions.
Main Results:
- Butylated hydroxytoluene (BHT) molecules were found to be dispersed throughout the alkyl-chain region of DPPC bilayers, irrespective of cholesterol presence.
- The chromanol ring of delta-tocopherol was localized near the glycerol backbone-headgroup region in both DPPC and DPPC-cholesterol bilayers.
- Difference Patterson maps confirmed the precise localization of bromine atoms in brominated delta-tocopherol samples, but not in brominated BHT samples.
Conclusions:
- SAXD successfully elucidated the distinct localization of BHT and delta-tocopherol within DPPC lipid bilayers.
- BHT integrates into the hydrophobic core, while delta-tocopherol's polar head interacts with the bilayer interface.
- The findings provide critical insights into the structural organization and interactions of antioxidants within membrane models.
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