IMPROVEMENT OF X-RAY POWDER-DIFFRACTION PATTERNS OF SALMONELLA-MINNESOTA DEEP ROUGH MUTANT BACTERIAL LIPOPOLYSACCHARIDE-INDUCED BY HEATING PLUS HYDRATION

The effects of different sample treatments on the X-ray powder-diffrac tion patterns of Salmonella minnesota R595 deep rough mutant bacterial lipopolysaccharides (LPS) were investigated. Samples were obtained by slow evaporation of aqueous solutions or suspensions of sodium, lithi um and natural salt form lipids. Samples were treated by hydration in moist air, heating to 60 degrees C and heating plus hydration. While a fter heating of samples no changes in diffraction patterns were observ ed, other treatments resulted in the improvement of peak intensities a nd sharpness of reflections. Heating plus hydration gave the most sign ificant effects. For one natural salt form LPS sample the treatments r esulted in almost doubling of the number of observable: reflections wi th the highest order found at 2 theta = 36 degrees. It is discussed th at the effects of treatments are most probably related to perfection o f the lateral and the stacking order in the samples, rather than an im proved mosaic spread. The simplicity of our sample treatment:, make th em suitable fur application to other than lipopolpsaccharide samples, especially for samples prepared by the Langmuir-Blodgett method. (C) 1 998 Elsevier Science S.A.