FIG. 5.
Tryptophan fluorescence of toxin B at acidic and neutral pH. Toxin B (20 pmol) was dialyzed to pH 4.0 or 7.0, and the tryptophan fluorescence was determined. The fluorescent spectrum of each sample is shown and labeled; each spectrum represents the experimental sample minus background. Similar relative fluorescence was obtained in two consecutive repetitions of this experiment.