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Dioxygen solubility in aqueous phosphatidylcholine dispersions
E S Smotkin1, F T Moy, W Z Plachy
1Department of Chemistry and Biochemistry, San Francisco State University, CA 94132.
Biochimica Et Biophysica Acta
|January 9, 1991
Summary
Molecular oxygen solubility in dimyristoylphosphatidylcholine (DMPC) dispersions is four times higher in liquid crystalline bilayers than in gel state bilayers. This difference is observed across temperatures, with gel state solubility similar to water.
Area of Science:
- Biophysics
- Physical Chemistry
- Materials Science
Background:
- Understanding gas solubility in lipid bilayers is crucial for biological and material applications.
- Dimyristoylphosphatidylcholine (DMPC) is a common phospholipid model system for studying membrane properties.
- Previous measurements of oxygen solubility in lipid systems have varied, necessitating further investigation.
Purpose of the Study:
- To accurately quantify the solubility of molecular oxygen (dioxygen) in aqueous dispersions of dimyristoylphosphatidylcholine (DMPC).
- To investigate the effect of temperature and lipid phase transitions (gel vs. liquid crystalline) on dioxygen solubility.
- To compare results with existing data, including those obtained using Electron Paramagnetic Resonance (EPR) spin labels.
Main Methods:
- Preparation of low weight percent (1.5%) sonicated DMPC aqueous dispersions.
- Measurement of dioxygen solubility using a modified Winkler technique with dual cell coulometric titration.
- Voltammetric endpoint detection in a methanol/water mixed solvent system.
- Temperature-dependent measurements conducted between 10°C and 40°C, spanning the DMPC phase transition (~24°C).
Main Results:
- Dioxygen solubility was found to be approximately four times greater in the liquid crystalline phase (above 24°C) compared to the gel phase (below 24°C) of DMPC bilayers.
- Dioxygen solubility showed minimal temperature dependence within each phase (gel or liquid crystalline).
- In the gel state, dioxygen solubility in DMPC bilayers was comparable to its solubility in water at the same temperature.
Conclusions:
- The phase state of DMPC bilayers significantly impacts molecular oxygen solubility, with the more fluid liquid crystalline phase accommodating higher concentrations.
- The observed solubility differences highlight the importance of lipid membrane structure in gas transport and partitioning.
- These findings provide a more precise understanding of oxygen behavior in lipid systems and offer a basis for re-evaluating previous experimental data.