title: Membrane-permeable and -impermeable sensors of the Zinpyr family and their application to imaging of hippocampal zinc in vivo.
abstract: Esterification of fluorescent biosensors is a common strategy used to trap probes within the cell. Zinpyr-1 (ZP1) is a fluorescein-based bright fluorescent sensor for divalent zinc that is cell permeable without prior modification. We describe here the synthesis and characterization of ZP1 sensors containing a carboxylic acid or ethyl ester functionality at the 5 or 6 position of the fluorescein. The presence of an electronegative carboxylate decreases the proton-induced background fluorescence of the probe by lowering the pKa of the benzylic amines responsible for fluorescence quenching. The charged species ZP1(6-CO2-) is membrane-impermeant, whereas the permeability of the neutral ZP1(5/6-CO2Et) is similar to that of the parent sensor. Intracranial microinfusion of ZP1(6-CO2Et) into rat hippocampus produces reduced staining of vesicular zinc in neuropil and very clear delineation of zinc-positive injured neuronal somata and dendrites as compared with ZP1.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Carolyn C
authors.initials: CC
authors.lastname: Woodroofe
authors.forename: Rafik
authors.initials: R
authors.lastname: Masalha
authors.forename: Katie R
authors.initials: KR
authors.lastname: Barnes
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Frederickson
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D002462:Cell Membrane / Q000737:chemistry* / Q000502:physiology; D005452:Fluoresceins / Q000138:chemical synthesis / Q000737:chemistry*; D006367:HeLa Cells; D006624:Hippocampus / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015394:Molecular Structure; D009474:Neurons / Q000737:chemistry; D051381:Rats; D013050:Spectrometry, Fluorescence / Q000379:methods; D015032:Zinc / Q000032:analysis*
chemical_list: D005452:Fluoresceins; C501988:Zinpyr-4; D015032:Zinc; C501987:zinpyr-1