title: Synthesis and spectral characterization of a long-lifetime osmium (II) metal-ligand complex: a conjugatable red dye for applications in biophysics.
abstract: There is a need for luminescent probes, which display both long excitation and emission wavelengths and long decay times. We synthesized and characterized an osmium metal-ligand complex which displays a mean decay time of over 100 ns when bound to proteins. [Os(1,10-phenanthroline)2(5-amino-1,10-phenanthroline)[(PF6)2 can be excited at wavelengths up to 650 nm, and displays an emission maximum near 700 nm. The probe displays a modest but useful maximum fundamental anisotropy near 0.1 for 488-nm excitation, and thus convenient when using an argon ion laser. [Os(phen)2(aphen)](PF6)2 is readily activated to the isothiocyanate for coupling to proteins. When covalently linked to bovine serum albumin the intensity decay is moderately heterogeneous with a mean decay time of 145 ns. The anisotropy decay of the labeled protein displays a correlation time near 40 ns. This relatively long lifetime luminophores can be useful as a biophysical probe or in clinical applications such as fluorescence polarization immunoassays.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Murtaza
authors.forename: P
authors.initials: P
authors.lastname: Herman
authors.forename: J R
authors.initials: JR
authors.lastname: Lakowicz
mesh_terms: D001703:Biophysics / Q000379:methods; D004396:Coloring Agents / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D008163:Luminescent Measurements; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009992:Osmium / Q000737:chemistry*; D010618:Phenanthrolines / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013053:Spectrophotometry; D019265:Spectroscopy, Near-Infrared / Q000379:methods
chemical_list: D004396:Coloring Agents; D008024:Ligands; D009942:Organometallic Compounds; D010618:Phenanthrolines; D012710:Serum Albumin, Bovine; D009992:Osmium