title: Zn(2+) binding-enabled excited state intramolecular proton transfer: a step toward new near-infrared fluorescent probes for imaging applications.
abstract: In order to facilitate the in vivo study of zinc-related biology, it is essential to develop a zinc-selective sensor that exhibits both near-infrared (NIR) emission and larger Stokes shift. A fluorescent sensor, Zinhbo-5, has been constructed by using bis(benzoxazole) ligand with 2, 2'-dipicolylamine (DPA) as metal ion receptor. In aqueous solution, Zinhbo-5 exhibits high sensitivity (K(d)  = 2.58 nM(2) ) and selectivity for Zn(2+)  cation, revealing about 14-fold fluorescence enhancement upon zinc binding to give green emission. Remarkably, Zn(2+)  binding to Zinhbo-5 switches on the excited state intramolecular proton transfer (ESIPT), producing the desirable near-infrared region (over 710 nm) with large Stokes shift (ca. 240 nm). The new probe is demonstrated to be useful for in vivo imaging of the intracellular Zn(2+)  ion. The Zinhbo-5 is also useful for detecting zinc ion distribution during the development of living zebrafish embryos.
authors.affiliation: Department of Chemistry & Maurice, Morton Institute of Polymer Science, The University of Akron, Akron, OH 44325, USA.
authors.forename: Yongqian
authors.initials: Y
authors.lastname: Xu
authors.forename: Qin
authors.initials: Q
authors.lastname: Liu
authors.forename: Bairui
authors.initials: B
authors.lastname: Dou
authors.forename: Brian
authors.initials: B
authors.lastname: Wright
authors.forename: Jingyun
authors.initials: J
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Pang
mesh_terms: D001665:Binding Sites; D003287:Contrast Media / Q000138:chemical synthesis; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D007259:Infrared Rays; D008856:Microscopy, Fluorescence / Q000379:methods*; D053758:Nanoparticles / Q000648:ultrastructure; D011522:Protons
chemical_list: D003287:Contrast Media; D005456:Fluorescent Dyes; D011522:Protons