Patent ID: 7632655

Claim:
A method of determining the presence or activity of a botulinum toxin type A, comprising the steps of: (a) measuring fluorescence polarization of a botulinum toxin type A substrate by exciting said botulinum toxin type A substrate with plane polarized light, 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; (b) treating said botulinum toxin type A substrate with a sample, under conditions suitable for botulinum toxin type A protease activity; and (c) measuring fluorescence polarization of said treated botulinum toxin type A substrate by exciting said treated botulinum toxin type A substrate with plane polarized light; wherein an increase in said fluorescence polarization measured in step (c) relative to said fluorescence polarization measured in step (a) 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; wherein a decrease in said fluorescence polarization measured in step (c) relative to said fluorescence polarization measured in step (a) is indicative of the presence of said botulinum toxin type A in said sample due to complex formation of said clostridial toxin with said treated botulinum toxin type A substrate; and wherein no substantial change in said fluorescence polarization measured in step (c) relative to said fluorescence polarization measured in step (a) is indicative of the lack of presence or activity of said botulinum toxin type A in said sample.