Patent ID: 7674601

Claim:
A method of determining the presence or activity of a botulinum toxin type A, comprising the steps of: (a) treating with a sample, including a botulinum toxin type A, under conditions suitable for botulinum toxin type A protease activity, a botulinum toxin type A substrate, said botulinum toxin type A substrate comprising (i) a donor fluorophore; (ii) an acceptor having an absorbance spectrum overlapping the emission spectrum of said donor fluorophore; and (iii) a botulinum toxin type A recognition sequence comprising a cleavage site, wherein said cleavage site intervenes between said donor fluorophore and said acceptor; and (b) measuring fluorescence polarization of said treated botulinum toxin type A substrate by exciting said fluorophore with plane polarized light; wherein an increase in said fluorescence polarization is indicative of the activity of said botulinum toxin type A in said sample due to cleavage of said treated botulinum toxin type A substrate by said botulinum toxin type A; and wherein a decrease in said fluorescence polarization is indicative of the presence of said botulinum toxin type A in said sample due to complex formation of said botulinum toxin type A with said treated botulinum toxin type A substrate.