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Spiral packing and chiral selectivity in model membranes probed by phase-resolved sum-frequency generation microscopy
Alexander P Fellows1, Ben John1, Martin Wolf1
1Fritz-Haber-Institute of the Max-Planck-Society, Berlin, Germany.
Nature Communications
|April 11, 2024
Summary
Lipid domains in cell membranes exhibit chiral, spiraling molecular arrangements. This structure, dependent on lipid chirality, reveals fundamental differences between chiral membrane types, potentially explaining life's homochirality.
Area of Science:
- Membrane biophysics
- Soft matter physics
- Supramolecular chemistry
Background:
- Lipid rafts are critical for cellular functions, with their molecular organization influencing membrane properties.
- Previous studies suggested molecular anisotropy and chirality in lipid domains but lacked detailed structural information.
- Understanding in-plane molecular orientations is key to deciphering domain function.
Purpose of the Study:
- To fully determine the 3D molecular structure of micron-scale condensed lipid domains in model membranes.
- To investigate the relationship between lipid chirality and domain morphology.
- To explore the implications for membrane properties and the origin of homochirality.
Main Methods:
- Utilized phase-resolved sum-frequency generation (SFG) microscopy.
- Studied model membranes composed of mixed-chirality phospholipid monolayers.
- Analyzed mesoscopic structural chirality and in-plane molecular orientations.
Main Results:
- Discovered domains exhibit curved molecular directionality and spiraling mesoscopic packing.
- Found that both molecular orientation and spiral directionality are dependent on lipid chirality.
- Observed distinct, non-mirror-symmetric structures for different enantiomeric mixtures, indicating enantioselectivity.
Conclusions:
- Lipid domain formation is strongly enantioselective, with chirality dictating structure.
- Homo- and heterochiral membranes exhibit fundamental thermodynamic differences.
- Findings may offer insights into the evolutionary advantage of homochirality in biological systems.
