Tritium labeling of alpha-neurotoxins with N-succinimidyl[3H]propionate.

The 3H-labeling of alpha-bungarotoxin and erabutoxin b and N-succinimidyl[2,3-3H]-propionate was examined by varying the concentrations of the reagents. The reaction yielded mono- and di[3H]propionyl-alpha-bungarotoxins and mono[3H]propionyl-erabutoxin b, which were readily isolated by CM-Sephadex C-25 chromatography and isoelectric focusing. All of these derivatives have essentially the same biological properties as the native toxins. Peptide mapping analysis revealed that monopropionyl derivatives of both toxins, which were sharply focused as single components in isoelectric focusing, were each composed of 2-4 isomers.