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Calcium and spermine interaction with phospholipid bilayers: a 15N NMR study
1Laboratoire de RMN et Réactivité Chimique, UA CNRS no. 472, Centre de Recherche de Biologie et Physico-Chimie Cellulaires, Nantes, France.
Biochimie
|January 1, 1989
Summary
Calcium (Ca2+) binding to lipid membranes alters phospholipid order and decreases the pKa of dipalmitoylphosphatidylethanolamine (DPPE). This deprotonation may be crucial for membrane fusion processes.
Area of Science:
- Biochemistry
- Biophysics
- Membrane Biophysics
Background:
- Lipid membranes are crucial for cellular functions.
- Calcium ions and polyamines influence membrane properties and interactions.
Purpose of the Study:
- Investigate Ca2+ and spermine binding to mixed lipid membranes.
- Elucidate the effects on phospholipid head groups and pKa.
- Assess the role of deprotonation in membrane fusion.
Main Methods:
- Utilized 15N-NMR spectroscopy on 15N-labeled dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine (DPPE).
- Studied membrane models at varying pH (8.0-9.4) and in the presence of Ca2+ and spermine.
Main Results:
- Ca2+ binding decreased order parameters and chemical shift anisotropy for both DPPC and DPPE.
- Ca2+ and spermine binding reduced the pKa of DPPE's amino group.
- Spermine binding broadened spectral signals, indicating reduced mobility and increased steric bulk.
Conclusions:
- 15N-NMR is effective for studying mixed liposomes.
- Membrane surface deprotonation, induced by Ca2+ and spermine, is a potential prerequisite for membrane fusion.