Physical and structural properties of [Cu(BOT1)Cl]Cl, a fluorescent imaging probe for HNO
ABSTRACT Nitroxyl, or HNO, is involved in a number of important physiological processes, such as vascular relaxation and neuroregulation. Effective imaging tools are required in order to gain a deeper understanding of the in vivo mechanisms of these processes and to identify the endogenous sources of HNO. Here, we further investigate the physical properties of our previously reported fluorescent nitroxyl sensor, [Cu(BOT1)Cl]Cl (J. Am. Chem. Soc.2010, 132, 5536; BOT1=BODIPY·triazole, a tetradentate ligand). A new high-yielding synthetic procedure for BOT1 is reported. The X-ray crystal structures of two Cu(II) complexes of BOT1 are described. These structural studies show that the BOT1 ligand can form Cu(II) coordination complexes of both square-pyramidal and trigonal-bipyramidal geometries. Cyclic voltammograms of [Cu(BOT1)Cl]Cl were acquired, revealing the presence of a quasi-reversible feature at 130mV (vs the ferrocene/ferrocenium couple) in MeCN and at -40mV (vs Ag/AgCl) in aqueous buffer, which is assigned to the Cu(II)/Cu(I) couple. The reactivity of [Cu(BOT1)Cl]Cl with Angeli's salt, a stable source of HNO, was further investigated. A 1000-fold excess of Angeli's salt elicits an immediate 10-fold emission turn-on response of the sensor, consistent with our previous report. A new observation, reported here, is that the intensity of this turn-on emission diminishes at longer incubation times. Fluorescent imaging of nitroxyl by [Cu(BOT1)Cl]Cl in HeLa cells was carried out. Upon treatment of the cells with Angeli's salt, there was a modest 2-fold intracellular turn-on in emission intensity.
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ABSTRACT: A new family of benzoresorufin-based copper complexes for fluorescence detection of NO and HNO is reported. The copper complexes, CuBRNO1-3, elicit 1.5-4.8-fold emission enhancement in response to NO and HNO. The three sensors differ in the nature of the metal-binding site. The photophysical properties of these sensors are investigated with assistance from density functional theory calculations. The fluorescence turn-on observed upon reaction with HNO is an unexpected result that is discussed in detail. The utility of the new sensors for detecting HNO and NO in HeLa cells and RAW 264.7 macrophages is demonstrated.Inorganic Chemistry 03/2013; 52(6). DOI:10.1021/ic302793w · 4.79 Impact Factor
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ABSTRACT: Nitroxyl (HNO) is a one-electron-reduced and protonated derivative of nitric oxide (NO), and has characteristic biological and pharmacological effects distinct from those of NO. However, studies of its biosynthesis and activities are restricted by the lack of versatile HNO detection methods applicable to living cells. Here, we report the first metal-free and reductant-resistant HNO imaging probe available for use in living cells, P-Rhod. It consists of a rhodol derivative moiety as the fluorophore, linked via an ester moiety to a diphenylphosphino-benzoyl group, which forms an aza-ylide upon reaction with HNO. Intramolecular attack of the aza-ylide on the ester carbonyl group releases a fluorescent rhodol derivative. P-Rhod showed high selectivity for HNO in the presence of various biologically relevant reductants, such as glutathione and ascorbate, in comparison with previous HNO probes. We showed that P-Rhod can detect not only HNO enzymatically gen-erated in the horseradish peroxidase-hydroxylamine system in vitro, but also intracellular HNO release from Angeli's salt in living cells. These results suggest that P-Rhod is suitable for detection of HNO in living cells.Journal of the American Chemical Society 07/2013; 135(34). DOI:10.1021/ja404757s · 11.44 Impact Factor
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ABSTRACT: Two new 2,2'-bipyridine (bpy) derivatives containing ancillary BODIPY chromophores attached at the 5- and 5'-positions (BB3) or 6- and 6'-positions (BB4) were prepared and characterized. In this work, the basic photophysics, electrochemistry, and electrogenerated chemiluminescence (ECL) of BB3 and BB4 are compared with those previously reported for a related bpy-BODIPY derivative (BB2) (J. Phys. Chem. C 2011, 115, 17993-18001). Cyclic voltammetry revealed that BB3 and BB4 display reversible 2e(-) oxidation and reduction waves, which consist of two closely spaced (50-70 mV) 1e(-) events. This redox behavior is consistent with the frontier molecular orbitals calculated for BB3 and BB4 and indicates that the 2,2'-bipyridine spacer of each bpy-BODIPY homologue does not facilitate efficient electronic communication between the tethered indacene units. In the presence of a coreactant such as tri-n-propylamine (TPA) or benzoyl peroxide (BPO), BB3 and BB4 exhibit strong ECL and produce spectra that are very similar to their corresponding photoluminescence profiles. The ECL signal obtained under annihilation conditions, however, is significantly different and is characterized by two distinct bands. One of these bands is centered at ∼570 nm and is attributed to emission via an S- or T-route. The second band occurs at longer wavelengths and is centered around ∼740 nm. The shape and concentration dependence of this long-wavelength ECL signal is not indicative of emission from an excimer or aggregate, but rather it suggests that a new emissive species is formed from the bpy-BODIPY luminophores during the annihilation process.Journal of the American Chemical Society 08/2013; 135(36). DOI:10.1021/ja406731f · 11.44 Impact Factor