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Glycosphingolipid acyl chain order profiles: substituent effects
M R Morrow1, D Singh, C W Grant
1Department of Physics, Memorial University of Newfoundland, St. John's, Canada.
Biochimica Et Biophysica Acta
|May 4, 1995
Summary
This study used 2H-NMR to analyze glycosphingolipids (GSLs) in membranes, revealing their hydrophobic region
Area of Science:
- Membrane Biophysics
- Lipid Bilayer Structure
- Nuclear Magnetic Resonance Spectroscopy
Background:
- Glycosphingolipids (GSLs) are crucial membrane components with diverse fatty acid structures.
- Understanding GSL behavior within lipid bilayers, particularly in the presence of cholesterol, is essential for elucidating membrane function.
- Previous studies have characterized glycerolipid fatty acid behavior, but GSLs require specific investigation.
Purpose of the Study:
- To characterize the arrangement and behavior of the hydrophobic region of glycosphingolipids (GSLs) within phosphatidylcholine/cholesterol membranes.
- To compare the effects of different fatty acid structures on GSL order parameter profiles.
- To investigate the influence of cholesterol on GSLs with saturated and unsaturated fatty acids.
Main Methods:
- Utilized Deuterium Nuclear Magnetic Resonance (2H-NMR) spectroscopy to determine fatty acid order parameter profiles.
- Synthesized Galactosyl ceramides (GalCer) with various deuterated fatty acids (18:0, D-alpha-OH 18:0, 18:1, 24:0).
- Dispersed GSLs as minor components in liposomes composed of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and 23% cholesterol.
Main Results:
- GSL fatty acid order parameters were generally higher than those of equivalent glycerolipids in cholesterol-containing bilayers.
- The order of 18-carbon saturated GSL fatty acids was strikingly similar, with minor differences observed for alpha-hydroxylation.
- Unsaturated GSL fatty acids showed reduced order near the membrane surface but increased order in the bilayer midplane, likely due to cholesterol.
- Very long-chain GSLs exhibited a distinct order profile with a second plateau, characteristic of their structure.
Conclusions:
- GSLs exhibit distinct ordering properties within cholesterol-rich membranes compared to glycerolipids.
- Cholesterol significantly influences the ordering of unsaturated GSL fatty acids by restricting cis-double bond isomerization.
- The membrane area requirements for GSLs with saturated fatty acids are not strongly dependent on fatty acid length when GSLs are minor components.