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Differences in the physical properties of lipid monolayers and bilayers on a spherical solid support
F M Linseisen1, M Hetzer, T Brumm
1Department of Physics, University of British Columbia, Vancouver, Canada.
Biophysical Journal
|April 1, 1997
Summary
Supported lipid monolayers (DPPC-d62) show higher phase transition temperatures than bilayers. 2H-NMR and DSC reveal gel-fluid coexistence and curved structures in these supported lipid systems.
Area of Science:
- Lipid bilayer and monolayer biophysics
- Solid-supported lipid systems characterization
- Membrane biophysics
Background:
- Understanding lipid behavior on solid supports is crucial for biosensor and drug delivery applications.
- Supported lipid systems, such as monolayers and vesicles, mimic cell membrane environments.
- 1,2-dipalmitoyl-glycero-3-phosphocholine (DPPC) is a common model lipid for membrane studies.
Purpose of the Study:
- To investigate the phase behavior and structural properties of a supported lipid monolayer (DPPC-d62) on silica beads.
- To compare the characteristics of supported monolayers (SSM) with supported bilayers (SSV) and multilamellar vesicles (MLV).
- To determine the influence of lipid density on the phase transition temperature of supported monolayers.
Main Methods:
- 2H-Nuclear Magnetic Resonance (2H-NMR) spectroscopy to probe molecular order and dynamics.
- Differential Scanning Calorimetry (DSC) to determine phase transition temperatures.
- Preparation of spherical supported monolayers (SSM) and spherical supported vesicles (SSV) on silanized silica beads.
Main Results:
- The phase transition temperature (Tm) of supported monolayers (SSM) was significantly higher than that of bilayer systems (SSV, MLV).
- 2H-NMR indicated a coexistence of gel and fluid phases within the SSM transition region.
- Analysis of NMR line shapes suggested the presence of highly curved structures in the fluid phase of SSMs.
- Lateral diffusion coefficients in supported monolayers were found to be similar to those in bilayers.
Conclusions:
- Supported lipid monolayers exhibit distinct phase behavior compared to bilayers, with higher transition temperatures.
- The lipid density during preparation influences the phase transition temperature of supported monolayers.
- Supported lipid monolayers can form highly curved structures in the fluid phase.
- Lateral lipid mobility in supported monolayers is comparable to that in supported bilayers.