Differential fluorescence labelling with 5-dimethyl-aminonaphthalene-1-sulfonyl chloride of intact cells and isolated membranes in Salmonella typhimurium and Acholeplasma laidlawii

For fluorescence labelling intact cells and isolated cell envelopes (membranes) from Salmonella typhimurium and Acholeplasma laidlawii were treated with mixed dansylchloride-lecithin-cholesterol vesicles. This kind of dansylation, which has been supposed to be specific for cell surface proteins, produced fluorescent protein pattern after SDS-polyacrylamide gel electrophoresis only when isolated envelopes were dansylated. Acid hydrolysis of fluorescent cell envelopes of Salmonella typhimurium yielded O-dansyltryosine and epsilon-N-dansyl-lysine besides the free sulfonic acid and unidentified compounds. However, no fluorescent proteins were detectable in cell envelopes isolated from dansylated intact bacteria from Salmonella typhimurium. In accord Acholeplasma laidlawii showed only fluorescence from proteins with a molecular weight higher than 100000.