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An Infrared Reflection-Absorption Spectroscopic (IRRAS) Study of the Interaction of Lipid A and Lipopolysaccharide Re with Endotoxin-Binding Proteins

[ Vol. 5 , Issue. 6 ]

Author(s):

Andreas Kerth, Patrick Garidel, Jorg Howe, Christian Alexander, Jean-Pierre Mach, Thierry Waelli, Alfred Blume, Ernst Th. Rietschel and K. Brandenburg   Pages 535 - 542 ( 8 )

Abstract:


Lipopolysaccharides (LPS, endotoxins) are main constituents of the outer membranes of Gram-negative bacteria, with the ‘endotoxic principle’ lipid A anchoring LPS into the membrane. When LPS is removed from the bacteria by the action of the immune system or simply by cell dividing, it may interact strongly with immunocompetent cells such as mononuclear cells. This interaction may lead, depending on the LPS concentration, to beneficial (at low) or pathophysiological (at high concentrations) reactions, the latter frequently causing the septic shock syndrome. There is a variety of endogenous LPS-binding proteins. To this class belong lactoferrin (LF) and hemoglobin (Hb), which have been shown to suppress and enhance the LPS-induced cytokine secretion in mononuclear cells, respectively. To elucidate the interaction mechanisms of endotoxins with these proteins, we have investigated in an infrared reflection-absorption spectroscopy (IRRAS) study the interaction of LPS or lipid A monolayers at the air/water interface with LF and Hb proteins, injected into the aqueous subphase. The data are clearly indicative of completely different interaction mechanisms of the endotoxins with the proteins, with the LF acting only at the LPS backbone, whereas Hb incorporates into the lipid monolayer. These data allow an understanding of the different reactivities in the biomedicinal systems.

Keywords:

IRRAS, Lipid, Endotoxin-Binding Proteins, Lipopolysaccharides, immune system

Affiliation:

Forschungszentrum Borstel, Leibniz-Zentrum fur Medizin und Biowissenschaften, 23845 Borstel, Germany.



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