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Non-contact, Label-free Monitoring of Cells and Extracellular Matrix using Raman Spectroscopy
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Published on: May 29, 2012

Comparative effects of melittin and its hydrophobic and hydrophilic fragments on bilayer organization by Raman

I W Levin, F Lavialle, C Mollay

    Biophysical Journal
    |January 1, 1982
    PubMed

    Insights

    Melittin binding to lipid bilayers forms an immobilized lipid annulus, affecting membrane phase transitions. This boundary layer of lipids surrounds the polypeptide, influencing bilayer fluidity.

    Area of Science:

    • Membrane biophysics
    • Lipid-protein interactions
    • Spectroscopic analysis

    Background:

    • Lipid bilayers are fundamental to cell membranes.
    • Polypeptides like melittin can integrate into membranes.
    • Understanding lipid-protein interactions is crucial for membrane function.

    Purpose of the Study:

    • To investigate the structural changes in 1,2-dimyristoyl phosphatidylcholine (DMPC) bilayers upon incubation with melittin.
    • To characterize the immobilized lipid annulus formed around melittin.
    • To compare the effects of intact melittin versus its components on lipid behavior.

    Main Methods:

    • Raman spectroscopy was used to analyze C--H, C--D, and C--C stretching modes.
    • Temperature profiles were generated to observe phase transitions.
    • Varying lipid:protein mole ratios (25:1, 14:1, 10:1) were studied.

    Main Results:

    • Two order-disorder transitions were observed in DMPC-melittin systems.
    • Increased melittin concentration lowered the primary gel to liquid crystalline phase transition.
    • A distinct, fluidizing transition occurred in the immobilized boundary lipids.
    • An annulus of approximately five to seven lipids was estimated around melittin.

    Conclusions:

    • Melittin forms a defined immobilized lipid annulus within DMPC bilayers.
    • Both hydrophobic and hydrophilic portions of melittin contribute to lipid immobilization.
    • Lipid-protein interactions significantly alter membrane phase behavior and fluidity.

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