Assessment of the Multiphase Interaction between a Membrane Disrupting Peptide and a Lipid Membrane

International Centre of Biodynamics, Bucharest, Romania.
The Journal of Physical Chemistry B (Impact Factor: 3.3). 10/2009; 113(43):14369-80. DOI: 10.1021/jp905170u
Source: PubMed


Although modeling and experimental approaches to probe antimicrobial peptides-lipid membranes interaction have already been reported, quantitative evaluation of the whole process, including full dissolution of the lipid, is still missing. We report on the real-time assessment of the entire set of stages of melittin-membrane interaction, based on surface plasmon resonance (SPR) measurements, using supported lipid matrices on L1 sensors and long peptide injections. We advance a mathematical model which comprises a set of coupled kinetic equations and relates via the transfer matrix the evolution of lipid and peptide concentrations with the SPR sensorgram. Upon fitting the sensorgrams of melittin injections on POPC lipid matrices, in agreement with literature data, the model provides: association and dissociation rates, concentration thresholds, and evolution within each interacting layer of lipid and peptide concentrations as well as of peptide to lipid ratios. The proposed model combined with appropriate experimental protocols adds new depths to SPR investigation of peptide-lipid interaction offering a quantitative platform for research and controlled design of improved antimicrobial peptides. A wider applicability for quantitative assessment of other pore forming compounds on different lipid matrices is suggested.

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    • "In the membrane environment, melittin folds into amphiphilic α-helices with four positive charges located at the C-terminus. One widely accepted model believes that melittin at high concentrations can insert into (mostly as toroidal pores) a membrane and destabilize the membrane resulting in leakage of cell components and eventually cell death (the " carpet " mechanism) [25] [26]. Besides the lipid composition (e.g. "
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    ABSTRACT: Quartz crystal microbalance with dissipation (QCM-D) technique is one of the most effective methods to monitor the dynamic behaviors of a layer on a solid surface. Moreover, it has been reported recently that it is able to provide a fingerprint for the peptide-membrane interactions. In this work, QCM-D technique combined with computer simulations was employed to investigate the deposition and transformation of vesicles, as well as the subsequent membrane-melittin interactions on different substrates. A range of substrate surfaces, i.e. naked SiO2 without or with Au/polyelectrolyte coating, were produced. The nature of the substrate determined whether the adsorbed vesicles were present as a high-quality supported bilayer or an assembled vesicle matrix, which consequently influenced the membrane-melittin interactions. It was indicated by the related computer simulations that the lipid packing state of the membrane was a key factor to determine the mechanism of membrane-peptide interactions. Furthermore, this work might be a good example of the application of QCM-D for the exploration of membrane-active peptides.
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    ABSTRACT: The molecular-level interactions of an antimicrobial peptide melittin with supported membrane were studied by the combination of dissipative quartz crystal microbalance (QCM-D) experiments and computer simulations. We found the response behavior of lipids upon peptide adsorption greatly influence their interactions. The perturbance and reorientation of the lipid in liquid phase facilitate the insertion of melittin in a trans-membrane way, but in solid phase, asymmetrical membrane disruption happens. Apart from the lipid state, the local peptide-to-lipid ratio also affects the insertion capacity of melittin. When the local peptide number density is high, adjacent peptides can cooperatively penetrate into the membrane. This observation explains the occurrence of the conventional "carpet" mechanism.
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