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Structural Characterization of a Model Gram-Negative Bacterial Surface Using Lipopolysaccharides from Rough Strains of Escherichia coli

DOI: 10.1021/bm400356m DOI Help

Authors: Anton Le Brun (ANSTO) , Luke Clifton (ISIS) , Candice E. Halbert (Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee) , Binhua Lin (Consortium of Advanced Radiation Sources (CARS), University of Chicago, Chicago) , Mati Meron (Consortium of Advanced Radiation Sources (CARS), University of Chicago, Chicago) , Peter J. Holden (ANSTO) , Jeremy Lakey (Newcastle University) , Stephen A. Holt (ANSTO)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biomacromolecules , VOL 14 (6) , PAGES 2014 - 2022

State: Published (Approved)
Published: April 2013

Open Access Open Access

Abstract: Lipopolysaccharides (LPS) make up approximately 75% of the Gram-negative bacterial outer membrane (OM) surface, but because of the complexity of the molecule, there are very few model OMs that include LPS. The LPS molecule consists of lipid A, which anchors the LPS within the OM, a core polysaccharide region, and a variable O-antigen polysaccharide chain. In this work we used RcLPS (consisting of lipid A plus the first seven sugars of the core polysaccharide) from a rough strain of Escherichia coli to form stable monolayers of LPS at the air–liquid interface. The vertical structure RcLPS monolayers were characterized using neutron and X-ray reflectometry, while the lateral structure was investigated using grazing incidence X-ray diffraction and Brewster angle microscopy. It was found that RcLPS monolayers at surface pressures of 20 mN m–1 and above are resolved as hydrocarbon tails, an inner headgroup, and an outer headgroup of polysaccharide with increasing solvation from tails to outer headgroups. The lateral organization of the hydrocarbon lipid chains displays an oblique hexagonal unit cell at all surface pressures, with only the chain tilt angle changing with surface pressure. This is in contrast to lipid A, which displays hexagonal or, above 20 mN m–1, distorted hexagonal packing. This work provides the first complete structural analysis of a realistic E. coli OM surface model

Subject Areas: Biology and Bio-materials

Facility: (15ID-C) at the Advanced Photon Laboratory