Effect of Cholesterol on the Phase Change of Lipid Membranes by Antimicrobial Peptides

Abstract

Membrane disruption by an antimicrobial peptide (AMP) was investigated by measuring the 2 H solid-state nuclear magnetic resonance spectra of 1-palmitoyl-d 31 -2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC_d 31 ) in mixtures of POPC_d 31 /cholesterol and either magainin 2 or aurein 3.3 deposited on thin cover-glass plates. The line shapes of the experimental 2 H solid-state nuclear magnetic resonance (SSNMR) spectra were best simulated by assuming the coexistence of a mosaic spread of bilayers containing pore structures and a fasttumbling isotropic phase or a hexagonal phase. Within a few days of incubation in a hydration chamber, an isotropic phase and a pore structure were induced by magainin 2, while in case of aurein 3.3 only an isotopic phase was induced in the presence of a bilayer phase. After an incubation period of over 100 days, alignment of the bilayers increased and the amount of the pore structure decreased in case of magainin 2. In contrast with magainin 2, aurein 3.3 induced a hexagonal phase at the peptide-to-lipid ratio of 1/20 and, interestingly, cholesterol was not found in the hexagonal phase induced by aurein 3.3. The experimental results indicate that magainin 2 is more effective in disrupting lipid bilayers containing cholesterol than aurein 3.3.

An Inward-Rectifier Potassium Channel Coordinates the Properties of Biologically Derived Membranes

“…On an intermediate timescale (t c~1 ms), it was observed in which CP and rINEPT both yielded a poor signal because of decreased T 1r and T 2 relaxation times. Subsequent studies with lipid mixtures, including cholesterol (31,(42)(43)(44) and other lipids known to introduce liquid-ordered membrane behavior (45)(46)(47)(48), found that CP and rINEPT can both endure under identical conditions, ostensibly because t c is on the fast timescale to facilitate rINEPT, although the internal lipid order parameter (S CH ) is great enough to permit CP. However, translational diffusion was not explicitly addressed in any of these studies and could make an additional contribution to 1 H and 13 C T 2 relaxation times in liposomes, helping to explain why rINEPT and CP can both be observed in some lipid populations.…”