title: Developing Activity Localization Fluorescence Peptide Probe Using Thiol-Ene Click Reaction for Spatially Resolved Imaging of Caspase-8 in Live Cells.
abstract: Small molecule probes suitable for high-resolution fluorescence imaging of enzyme activity pose a challenge in chemical biology. We developed a novel design of activity localization fluorescence (ALF) peptide probe, which enables spatially resolved, highly sensitive imaging of peptidase in live cells. The ALF probe was synthesized by a facile thiol-ene click reaction of a cysteine-appended peptide with an acryloylated fluorophore. Upon cleavage by peptidase, the probe undergoes a seven-membered intramolecular cyclization and releases the fluorophore with the excited-state intramolecular photon transfer (ESIPT) effect. A highly fluorescent, insoluble aggregate was formed around the enzyme, which facilitates high-sensitivity and high-resolution imaging. This design is demonstrated for detection of caspase-8 activation. The results show that our design allows easy, high-yield synthesis of the probe, and the probe affords high sensitivity for caspase-8 detection. Live cell imaging reveals that the probe is able to render highly localized and high-contrast fluorescence signal for caspase-8. Our design holds the potential as a generally applicable strategy for developing high-sensitivity and high-resolution imaging peptide probes in cell biology and diagnostics.
authors.affiliation: Institute of Chemical Biology & Nanomedicine, State Key Laboratory of Chemo/Biosensing & Chemometrics, College of Chemistry & Chemical Engineering, Hunan University , Changsha 410082, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.affiliation: Guangxi Collaborative Innovation Center for Biomedicine & School of Preclinical Medicine, Guangxi Medical University , Nanning 530021, China.
authors.forename: Si-Jia
authors.initials: SJ
authors.lastname: Liu
authors.affiliation: Institute of Chemical Biology & Nanomedicine, State Key Laboratory of Chemo/Biosensing & Chemometrics, College of Chemistry & Chemical Engineering, Hunan University , Changsha 410082, China.
authors.forename: Yong-Qing
authors.initials: YQ
authors.lastname: Kuang
authors.affiliation: Institute of Chemical Biology & Nanomedicine, State Key Laboratory of Chemo/Biosensing & Chemometrics, College of Chemistry & Chemical Engineering, Hunan University , Changsha 410082, China.
authors.forename: Feng-Yan
authors.initials: FY
authors.lastname: Luo
authors.affiliation: Institute of Chemical Biology & Nanomedicine, State Key Laboratory of Chemo/Biosensing & Chemometrics, College of Chemistry & Chemical Engineering, Hunan University , Changsha 410082, China.
authors.forename: Jian-Hui
authors.initials: JH
authors.lastname: Jiang
mesh_terms: D053181:Caspase 8 / Q000032:analysis*; D057930:Click Chemistry; D003500:Cyclization; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D010455:Peptides / Q000737:chemistry*; D017785:Photons; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D010455:Peptides; D013438:Sulfhydryl Compounds; D053181:Caspase 8