title: Design and synthesis of a new class of membrane-permeable triazaborolopyridinium fluorescent probes.
abstract: A new class of fluorescent triazaborolopyridinium compounds was synthesized from hydrazones of 2-hydrazinylpyridine (HPY) and evaluated as potential dyes for live-cell imaging applications. The HPY dyes are small, their absorption/emission properties are tunable through variation of pyridyl or hydrazone substituents, and they offer favorable photophysical characteristics featuring large Stokes shifts and general insensitivity to solvent or pH. The stability, neutral charge, cell membrane permeability, and favorable relative influences on the water solubility of HPY conjugates are complementary to existing fluorescent dyes and offer advantages for the development of receptor-targeted small-molecule probes. This potential was assessed through the development of a new class of cysteine-derived HPY-conjugate imaging agents for the kinesin spindle protein (KSP) that is expressed in the cytoplasm during mitosis and is a promising chemotherapeutic target. Conjugates possessing the neutral HPY or charged Alexa Fluor dyes that function as potent, selective allosteric inhibitors of the KSP motor were compared using biochemical and cell-based phenotypic assays and live-cell imaging. These results demonstrate the effectiveness of the HPY dye moiety as a component of probes for an intracellular protein target and highlight the importance of dye structure in determining the pathway of cell entry and the overall performance of small-molecule conjugates as imaging agents.
authors.affiliation: Department of Chemistry and Biochemistry, New Mexico State University, MSC 3C, Las Cruces, New Mexico 88003, USA.
authors.forename: Sudath
authors.initials: S
authors.lastname: Hapuarachchige
authors.forename: Gilbert
authors.initials: G
authors.lastname: Montaño
authors.forename: Chinnasamy
authors.initials: C
authors.lastname: Ramesh
authors.forename: Delany
authors.initials: D
authors.lastname: Rodriguez
authors.forename: Lauren H
authors.initials: LH
authors.lastname: Henson
authors.forename: Casey C
authors.initials: CC
authors.lastname: Williams
authors.forename: Samuel
authors.initials: S
authors.lastname: Kadavakkollu
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Johnson
authors.forename: Charles B
authors.initials: CB
authors.lastname: Shuster
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Arterburn
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D002463:Cell Membrane Permeability; D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D011726:Pyridinium Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism*; D011728:Pyridones / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D011728:Pyridones; C062607:2-hydrazinopyridine