Interaction of pyrene-labeled monosialoganglioside GM1 micelles with cholera toxin.

Monosialoganglioside GM1 labeled with 1-pyrene-dodecanoic acid was used to monitor interactions between cholera toxin and its receptor. Binding of cholera toxin to labeled ganglioside caused a decrease in pyrene fluorescence intensity at 480 nm concomitant with an increase in fluorescence intensity at 380 and 398 nm. The observed fluorescence changes are similar to those observed when fluorescent ganglioside is moved from an aqueous solvent to an organic solvent. The data are consistent with cholera toxin-bound ganglioside undergoing a process resembling solvent-dependent molecular dispersion.