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Phosphorus-31 two-dimensional solid-state exchange NMR. Application to model membrane and biological systems.
1Division of Biological Sciences, National Research Council of Canada, Ottawa, Ontario.
Biophysical Journal
|January 1, 1991
Summary
Two-dimensional solid-state 31P NMR reveals phospholipid orientational exchange rates in various membrane phases. Biological membranes exhibit significantly slower exchange than model systems, suggesting smoother cell surfaces.
Area of Science:
- Solid-state NMR spectroscopy
- Biophysics
- Materials Science
Background:
- Phospholipids form biological membranes, crucial for cell function.
- Understanding phospholipid dynamics is key to membrane function.
- Solid-state NMR provides insights into molecular motion within membranes.
Purpose of the Study:
- Investigate phospholipid orientational exchange in different membrane phases (gel, liquid-crystalline, ripple).
- Determine lateral diffusion correlation times (τd) using 2D NMR.
- Compare dynamics in model lipid systems with biological membranes.
Main Methods:
- Two-dimensional solid-state 31P NMR spectroscopy.
- Spectral simulations to determine exchange correlation times.
- Analysis of phospholipid dispersions, oriented multibilayers, and biological membranes (erythrocyte ghosts, spinal cord).
Main Results:
- Liquid-crystalline phase shows faster exchange (τd ~8-44 ms for DMPC, DPPC) due to lateral diffusion.
- Gel phase exhibits significantly slower exchange (τd ~900 ms for DPPC).
- Biological membranes (erythrocyte ghosts, spinal cord) show slower exchange (τd ~400 ms - 1.3 s) compared to model systems.
Conclusions:
- Lateral diffusion rates vary significantly across phospholipid phases.
- Biological membranes are dynamically less mobile than model systems.
- Slower exchange in biological membranes suggests a relatively smooth cell surface with minimal perturbations impacting phospholipid orientation.