Patent ID: 8048643

Claim:
A Clostridial toxin substrate, comprising: a) a donor fluorophore; b) an acceptor having an absorbance spectrum overlapping the emission spectrum of said donor fluorophore; and c) a Clostridial toxin recognition sequence comprising a Clostridial P 5 -P 4 -P 3 -P 2 -P 1 -P 1 ′-P 2 ′-P 3 ′-P 4 ′-P 5 ′ cleavage site sequence, said Clostridial P 5 -P 4 -P 3 -P 2 -P 1 -P 1 ′-P 2 ′-P 3 ′-P 4 ′-P 5 ′ cleavage site sequence intervening between said donor fluorophore and said acceptor; wherein, under the appropriate conditions, resonance energy transfer is exhibited between said donor fluorophore and said acceptor.