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[Polymyxin B and Ca(2+) induce conductance fluctuations in the dipalmitoyl phosphatidic acid bilayer lipid membrane]
E A Korepanova1, E V Shevchenko, E T Kozhomkulov
1Russian State Medical University, Moscow, Russia.
Abstract:
Polymyxin B in micromolar concentrations induces current fluctuations in liquid crystalline bilayer lipid membranes from dipalmitoylphosphatidic acid identified as ion channels. The appearance of ion channels correlates with phase separation of the lipid in the presence of peptide polycations detected by differential scanning calorimetry. Ca2+ also induces the formation of ion channels in liquid crystalline bilayer lipid membranes from dipalmitoylphosphatidic acid followed by the phase transition of the phospholipid. The capacitive current, which indicates the possibility of structural transformations of bilayer-non-bilayer type (hexagonal phase II), precedes the formation of Ca(2+)-induced channels in bilayer lipid membranes from dipalmitoylphosphatidic acid.
Insights
Polymyxin B and Ca2+ create ion channels in lipid membranes by inducing lipid phase separation. This structural change, detected by calorimetry, is crucial for channel formation in dipalmitoylphosphatidic acid membranes.
Area of Science:
- Biophysics
- Membrane Biophysics
- Lipid Bilayer Studies
Background:
- Lipid bilayer membranes are fundamental to cell structure and function.
- Understanding ion channel formation is critical for pharmacology and cell physiology.
- Dipalmitoylphosphatidic acid (DPPA) is a common phospholipid model system.
Purpose of the Study:
- To investigate the mechanism of ion channel formation in DPPA lipid membranes induced by Polymyxin B and Ca2+.
- To correlate ion channel appearance with lipid structural changes.
- To explore the role of phase transitions in channel formation.
Main Methods:
- Electrophysiology to detect current fluctuations (ion channels).
- Differential scanning calorimetry (DSC) to monitor lipid phase transitions.
- Utilizing liquid crystalline bilayer lipid membranes composed of dipalmitoylphosphatidic acid.
Main Results:
- Polymyxin B induced ion channel activity in DPPA membranes at micromolar concentrations.
- Ion channel formation correlated with lipid phase separation, detected by DSC.
- Ca2+ also induced ion channels in DPPA membranes, accompanied by phospholipid phase transitions.
- Capacitive currents indicated bilayer-to-non-bilayer (hexagonal phase II) transitions preceding Ca2+-induced channel formation.
Conclusions:
- Polymyxin B and Ca2+ act as inducers of ion channel formation in DPPA lipid membranes.
- Lipid phase separation and structural transitions are key events in the mechanism of ion channel formation.
- These findings provide insights into the interaction of peptides and ions with lipid membranes.