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  • Title: Impact of the antimicrobial peptide Novicidin on membrane structure and integrity.
    Author: Nielsen SB, Otzen DE.
    Journal: J Colloid Interface Sci; 2010 May 15; 345(2):248-56. PubMed ID: 20153477.
    Abstract:
    We have studied the impact of an 18-residue cationic antimicrobial peptide Novicidin (Nc) on the structure and integrity of partially anionic lipid membranes using oriented circular dichroism (OCD), quartz crystal microbalance with dissipation (QCM-D), dual polarization interferometry (DPI), calcein dye leakage and fluorescence spectroscopy. OCD consistently showed that Nc is bound in an α-helical, surface bound state over a range of peptide to lipid (P/L) ratios up to ~1:15. Realignment of Nc at higher P/L ratios correlates to loss of membrane integrity as shown by Laurdan fluorescence spectroscopy and by loss of lipid alignment in DPI analysis. Laurdan generalized polarity shows a decrease in water accessibility or mobility in the hydrophobic/hydrophilic interface of the lipid membrane, consistent with rearrangement of lipid packing. QCM-D studies on the interaction of Nc with lipid membranes emphasize the importance of including the dissipation factor in data analysis, revealing formation of a highly hydrated film after exposure to ≥3 μM Nc. Our findings suggest a carpet mechanism of membrane disruption in which peptide binding first induces leakage at a critical surface concentration, probably through formation of transient pores or transient disruption of the membrane integrity, followed by more extensive membrane disintegration at higher P/L ratios.
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