Journal
COMPTES RENDUS CHIMIE
Volume 12, Issue 1-2, Pages 209-217Publisher
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
DOI: 10.1016/j.crci.2008.06.020
Keywords
Lipopolysaccharide; Antibacterial peptide; Monolayer; Grazing-incidence X-ray scattering; Monte Carlo simulation
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Funding
- Deutsche Forschungsgerneinschaft
- Fonds der Chemischen Industrie
- Natural Sciences and Engineering Research Council (NSERC) of Canada.
- Canadian Advanced Foods and Materials Network
- U.S. National Science Foundation [DMR-0206681]
- Alexander von Humboldt Foundation
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The combination of grazing-incidence X-ray scattering experiments and Monte Carlo simulation unravels the physics of bacterial survival against cationic antimicrobial peptides (protamine). As a realistic model of bacterial outer membranes, an insoluble monolayer of lipopolysaccharide from Salmonella enterica sv. Minnesota Ra (LPS Ra) is spread on buffered subphase. In the presence of Ca2+, vertical electron density profiles reconstructed from X-ray scattering imply the collapse of saccharide chains, suggesting that Ca2+ bridges the negatively charged saccharide units. Under this condition, the LPS monolayer remains intact even after injection of protamine near the minimum inhibitory concentration. This can theoretically be accounted in terms of the formation of an electrostatic energy barrier that prevents the approach of protamine to the hydrophobic region. In contrast, as predicted from in vivo experiments, the intrusion of protamine in the absence of Ca2+ results in the complete destruction of the layered structure of LPS Ra monolayers. To cite this article: Rafael G. Oliveira et al., C. R. Chimie 12 (2009). (C) 2008 Academic des sciences. Published by Elsevier Masson SAS. All rights reserved.
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