Physical and structural properties of [Cu(BOT1)Cl]Cl, a fluorescent imaging probe for HNO

Massachusetts Institute of Technology, Department of Chemistry, Cambridge, MA 02139, USA.
Journal of inorganic biochemistry (Impact Factor: 3.27). 10/2012; 118. DOI: 10.1016/j.jinorgbio.2012.08.025
Source: PubMed

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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Nitroxyl (HNO) donors exhibit promising pharmacological characteristics for treatment of cardiovascular disorders, cancer and alcoholism. However, whether HNO also serves as an endogenous signaling agent is currently unknown, largely due to the inability to selectively and sensitively detect HNO in a cellular environment. Although a number of methods to detect HNO have been developed recently, sensitivity and selectivity against other nitrogen oxides or biological reductants remain problematic. To improve selectivity, the electrophilic nature of HNO has been harnessed to generate modifications of thiols and phosphines that are unique to HNO, especially compared to nitric oxide (NO). Given high bioavailability, glutathione (GSH) is expected to be a major target of HNO. As a result, the putative selective product glutathione sulfinamide (GS(O)NH2) may serve as a high yield biomarker of HNO production. In this work, the formation of GS(O)NH2 following exposure to HNO donors was investigated. Fluorescent labeling followed by separation and detection using capillary zone electrophoresis with laser-induced fluorescence allowed quantitation of GS(O)NH2 with nanomolar sensitivity, even in the presence of GSH and derivatives. Formation of GS(O)NH2 was found to occur exclusively upon exposure of GSH to HNO donors, thus confirming selectively. GS(O)NH2 was detected in the lysate of cells treated with low micromolar concentrations of HNO donors, verifying that this marker has sufficient stability to server as a biomarker of HNO. Additionally, the concentration-dependent formation of GS(O)NH2 in cells treated with an HNO donor suggests that the concentration of GS(O)NH2 can be correlated to intracellular levels of HNO.
    Free Radical Biology and Medicine 07/2014; DOI:10.1016/j.freeradbiomed.2014.07.022 · 5.71 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Terminal fluoride complexes of the monovalent group 11 metals, supported by N-heterocyclic carbene (NHC) ligands, react with one-half equivalent of triphenylmethyl cation to form fluoride-bridged dinuclear cations. An improved preparation of the starting terminal fluorides is introduced. The crystal structures of the cations display bent M-F-M arrangements with large intermetallic separations. The bridging fluorides are highly labile, undergoing facile hydrolysis. The fluoride-bridged digold complex adds across an allene C=C bond to form a diaurated allylic fluoride.
    Polyhedron 12/2014; 84:87-95. DOI:10.1016/j.poly.2014.06.039 · 2.05 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Selected meso BODIPYs (chemically reactive, difficult to obtain by established procedures, or photophysically or electrochemically attractive) have been obtained by unprecedented selective lateral lithiation of 8-methylBODIPYs. The physical study of the obtained new meso BODIPYs reveals interesting tunable properties related to the activation of intramolecular charge-transfer processes, endorsing the new synthetic methodology as useful for the development of smarter BODIPY dyes for technological applications.
    Organic Letters 08/2014; 16(17). DOI:10.1021/ol501945v · 6.32 Impact Factor