High state of order of isolated bacterial lipopolysaccharide and its possible contribution to the permeation barrier property of the outer membrane.

摘要: The conformational properties of the isolated S form Salmonella sp. lipopolysaccharide (LPS), Re mutant LPS, and free lipid A were investigated by using X-ray diffraction energy calculations. data obtained showed that LPS in a dried, hydrated, probably also an aqueous dispersion state is capable forming bilayered lamellar arrangements similar to phospholipids. From bilayer packing periodicities, geometrical model extensions regions A, 2-keto-3-deoxyoctulosonic acid, O-specific chain along membrane normal could be calculated. Furthermore, component was found assume remarkably high ordered conformation: its fatty acid chains tightly packed dense hexagonal lattice with center-to-center distance 0.49 nm. hydrophilic backbone strong tendency domains membrane, resulting more or less parallel arrangement units. According calculations, appears oriented approximately 45 degrees surface, which would lead shed roof-like appearance surface structure indentations moiety fit. In contrast, low ordered, heavily coiled conformation. Comparison these structural those known for natural phospholipids biological membranes indicates order portion might important factor role permeation barrier functions outer gram-negative bacteria.