Proteins from Salmonella R-mutants mediating protection against Salmonella typhimurium infection in mice I. Preparation of proteins free from lipopolysaccharide using various chromatographic methods.

Different chromatographic methods are described to remove traces of LPS from proteins extracted from the surface of several R-mutants of Salmonella. The protein preparations obtained by these methods were found to contain less than 0.001% of beta-hydroxymyristic acid as determined by gas liquid chromatography. This corresponds to less than 0.003 to 0.006% of R-form-LPS (depending on the chemotype of the mutant) and less than 0.014% of S-form-LPS. From some protein mixtures LPS could be removed by repeated gel filtration on a column of Sepharose CL-6B. Recycling gel filtration proved to be more effective considering the high recovery of protein in much shorter time. Ion exchange chromatography on DEAE Sepharose CL-6B was also useful in some cases. Thus, using one or the other method LPS free protein preparations could be obtained with extracts obtained from 6 out of 7 bacterial strains.