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Atomic Force Microscopy Imaging and Force Spectroscopy of Supported Lipid Bilayers
Published on: July 22, 2015
Structural changes in dipalmitoylphosphatidylcholine bilayer promoted by Ca2+ ions: a small-angle neutron scattering
Daniela Uhríková1, Norbert Kucerka, José Teixeira
1Department of Physical Chemistry of Drugs, Faculty of Pharmacy, Comenius University, Odbojárov 10, 832 32 Bratislava, Slovakia. daniela.uhrikova@fpharm.uniba.sk
Chemistry and Physics of Lipids
|August 30, 2008
Summary
Calcium ions alter dipalmitoylphosphatidylcholine (DPPC) lipid bilayer structure, affecting thickness and water content. These changes depend on temperature and calcium concentration, with significant effects observed below 10mM CaCl2.
Area of Science:
- Biophysics
- Materials Science
- Physical Chemistry
Background:
- Unilamellar dipalmitoylphosphatidylcholine (DPPC) vesicles are model systems for biological membranes.
- Calcium ions (Ca2+) are known to interact with phospholipid bilayers, influencing their structure and function.
Purpose of the Study:
- To investigate the structural changes in DPPC lipid bilayers induced by varying concentrations of CaCl2.
- To determine the binding fraction of Ca2+ ions in the DPPC polar head group region.
Main Methods:
- Small-angle neutron scattering (SANS) was employed to analyze DPPC vesicle structures.
- A strip-function model was used to interpret the SANS data.
- Langmuir adsorption isotherm was utilized to quantify Ca2+ binding.
Main Results:
- In the gel phase (20°C), DPPC bilayer thickness (dL) peaked at ~2.5mM CaCl2, while area per DPPC molecule (AL) and water content (nW) decreased.
- In the fluid phase (60°C), structural parameters (dL, AL, nW) changed significantly with Ca2+ up to 10mM.
- DPPC bilayers in 60mM CaCl2 showed structural parameters similar to vesicles without Ca2+.
Conclusions:
- Calcium binding to DPPC head groups induces significant structural modifications in lipid bilayers.
- Temperature plays a crucial role in modulating the effects of calcium on DPPC bilayer structure.
- High calcium concentrations may saturate binding sites, leading to structural parameters resembling those of calcium-free vesicles.
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