Neutrophil Elastase Activity Imaging: Recent Approaches in the Design and Applications of Activity-Based Probes and Substrate-Based Probes

Figure 3

Protease-sensitive probes for optical imaging. (a) Fluorogenic (F)/chromogenic (C) enzyme-sensitive probe. One fluorescent or chromogenic molecule is bound to a peptide. Spectroscopic properties will be altered upon proteolysis. (b) Fluorophore-quencher type probe. Förster resonance energy transfer- (FRET-) based probes require a donor and an acceptor fluorophore pair each saturated on one side of the enzyme cleavage site. (c) Polymeric-peptide conjugate probe. Overabundance of fluorophores coupled to a polymer backbone via a peptide substrate. Black arrowheads depict cleavage site within the amino acid sequence.

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