Abstract
Synthetic Escherichia coli-type lipid A formed hexagonal plate crystals when it was precipitated by the addition of 2 volumes of 95% ethanol containing 375mM MgCl2 and incubated in 70% ethanol containing 250mM MgCl2 at 4C for 10 days. Analyses of crystals by electron diffraction and synchrotron Xray diffraction showed that crystals consist of hexagonal lattices with the lattice constant (a side of the lozenge as a unit cell on the basal plane) of 4.62Å and the longitudinal axis (perpendicular to the basal plane) of 49.3±1.3Å. Results suggest that the previous finding that various kinds of R-form lipopolysaccharides crystallized but free lipid A isolated by acid hydrolysis from Re lipopolysaccharide did not crystallize under the same experimental conditions (Kato et al, J. Bacteriol., 172: 1516-1528, 1990) is due to structural changes of lipid A occurring during the procedure of isolation of free lipid A.
