title: Bacterial lipopolysaccharides form physically cross-linked, two-dimensional gels in the presence of divalent cations.
abstract: We established a bacterial membrane model with monolayers of bacterial lipopolysaccharides (LPS Re and LPS Ra) and quantified their viscoelastic properties by using an interfacial stress rheometer coupled to a Langmuir film balance. LPS Re monolayers exhibited purely viscous behaviour in the absence of calcium ions, while the same monolayers underwent a viscous-to-elastic transition upon compression in the presence of Ca(2+). Our results demonstrated for the first time that LPSs in bacterial outer membranes can form two-dimensional elastic networks in the presence of Ca(2+). Different from LPS Re monolayers, the LPS Ra monolayers showed a very similar rheological transition both in the presence and absence of Ca(2+), suggesting that longer saccharide chains can form 2D physical gels even in the absence of Ca(2+). By exposure of the monolayers to the antimicrobial peptide protamine, we could directly monitor the differences in resistance of bacterial membranes according to the presence of calcium.
authors.affiliation: Physical Chemistry of Biosystems, Institute of Physical Chemistry, University of Heidelberg, D69120 Heidelberg, Germany. tanaka@uni-heidelberg.de.
authors.forename: Moritz
authors.initials: M
authors.lastname: Herrmann
authors.forename: Emanuel
authors.initials: E
authors.lastname: Schneck
authors.forename: Thomas
authors.initials: T
authors.lastname: Gutsmann
authors.forename: Klaus
authors.initials: K
authors.lastname: Brandenburg
authors.forename: Motomu
authors.initials: M
authors.lastname: Tanaka
mesh_terms: D001419:Bacteria / Q000737:chemistry; D055592:Biophysical Phenomena; D002118:Calcium / Q000737:chemistry; D002413:Cations, Divalent / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008070:Lipopolysaccharides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*
chemical_list: D002413:Cations, Divalent; D003432:Cross-Linking Reagents; D007477:Ions; D008070:Lipopolysaccharides; D010455:Peptides; D002118:Calcium