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Investigation of Gramicidin A Incorporation into Phospholipid Vesicle Bilayers Using Optical-Trapping Confocal Raman
Jay P Kitt1,2, Joel M Harris1
1Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850 USA.
Applied Spectroscopy
|May 4, 2026
Summary
Pore-forming peptides like gramicidin A disrupt cell membranes by altering lipid structures. This study used Raman microscopy to show gramicidin A causes disorder in lipid bilayers, impacting 7-8 surrounding lipids per peptide.
Area of Science:
- Biophysics
- Membrane biophysics
- Spectroscopy
Background:
- Pore-forming peptides are crucial membrane-active molecules that disrupt cellular homeostasis by forming ion channels.
- Understanding peptide-induced lipid bilayer perturbations is vital for designing new antimicrobials.
Purpose of the Study:
- To investigate the structural impact of gramicidin A (gA) on 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) phospholipid bilayers.
- To quantify the relationship between gA concentration and lipid bilayer disorder using optical-trapping confocal Raman microscopy.
Main Methods:
- Utilized optical-trapping confocal Raman microscopy to study individual DMPC vesicles.
- Acquired Raman spectra to identify peptide-specific markers and analyze lipid chain dynamics.
- Applied self-modeling curve resolution to spectral data to resolve distinct lipid environments.
Main Results:
- Confirmed gA incorporation into DMPC bilayers via tryptophan vibrational markers.
- Observed systematic disordering of DMPC acyl chains with increasing gA concentration (0-20 mol%).
- Identified two lipid populations: ordered and gA-perturbed disordered, with the latter increasing linearly with gA concentration, impacting ~7-8 lipids per gA channel.
Conclusions:
- Gramicidin A incorporation deforms DMPC bilayers, causing localized lipid disorder due to hydrophobic mismatch.
- Optical-trapping confocal Raman microscopy is effective for quantitative, single-vesicle analysis of peptide-membrane interactions.
- Model-free spectral analysis can resolve peptide-induced structural changes in membranes.
