Nitrosyl hydride, HNO or nitroxyl, is the one-electron reduced and protonated form of nitric oxide. HNO is isoelectronic to singlet O 2 , and we have previously reported that deoxy myoglobin traps free HNO to form a stable adduct. In this report, we demonstrate that oxygen-binding hemoglobins from human, soy and clam also trap HNO to form adducts which are stable over a period of weeks. The same species can be formed in higher yield by careful reduction of the ferrous nitrosyl adducts of the proteins. Like the analogous O 2 -Fe II adducts, the HNO adducts are diamagnetic, but with a characteristic HNO resonance in 1 H NMR ca. 15 ppm that splits into doublets for H 15 NO adducts. The 1 H and 15 N NMR resonances, obtained by HSQC experiments, are shown to differentiate subunits and isoforms of proteins within mixtures. An apparent difference in reduction rates of the NO-adducts of the two subunits of human hemoglobin allows assignment of two distinct nitrosyl hydride peaks by a combination of UVvis, NMR and EPR analysis. The two peaks of HNO-hHb have a persistent 3:1 ratio during trapping reactions, demonstrating a kinetic difference between HNO binding at the two subunits. These results show NMR characterization of ferrous HNO adducts as a unique tool sensitive to structural changes within the oxygen-binding cavity, which may be of use in defining modes of oxygen binding in other heme proteins and enzymes. KeywordsHNO; nitroxyl; nitrosyl hydride; dioxygen; globins; heme oxygenase Nitrosyl hydride (HNO), the protonated form of nitroxyl anion (NO − ), has distinct physicochemical properties from its congener nitric oxide (NO), much of which has been defined only recently. 1,2 The anionic form is isoelectronic with dioxygen and exists as a triplet, 3 NO − above pH 12; at lower pH the singlet 1 HNO dominates, but is susceptible to rapid † This research was supported by the National Science Foundation (PJF CHE-0100774) and the National Institutes of Health (PJF 1R21ES016441-01).*To whom correspondence should be addressed. E-mail: pfarmer@uci.edu. . SUPPORTING INFORMATION AVAILABLE. Experimental details available include descriptions of peak fitting for isoforms of native legHb mixtures, timecourse UVvis spectra during the formation of HNO-hHb, EPR characterization of ferrous NO adduct impurities in HNO adduct samples and data for initial rate analysis of HNO trapping by deoxy Mb and hHb. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2010 June 9. The rate of this dimerization has been reported as 8 × 10 6 M −1 s −1,5 and thus severely limits the lifetime and concentration of HNO generated in solution.(1)HNO is the simplest analogue of alkylnitroso compounds, RNO, long known to bind to ferrous heme proteins. 6 Mansuy and coworkers were the first to describe the binding of RNO compounds to ferrous globins myoglobin (Mb) and human hemoglobin (hHb), 7 as well as to make the analogy of RNO bindi...

The encapsulation of bismuth as BiOCl/Bi2O3 within ultra-short (ca. 50 nm) single-walled carbon nanocapsules (US-tubes) has been achieved. The Bi@US-tubes have been characterized by high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Bi@US-tubes have been used for intracellular labeling of pig bone marrow-derived mesenchymal stem cells (MSCs) to show high X-ray contrast in computed tomography (CT) cellular imaging for the first time. The relatively high contrast is achieved with low bismuth loading (2.66% by weight) within the US-tubes and without compromising cell viability. X-ray CT imaging of Bi@US-tubes-labeled MSCs showed a nearly two-fold increase in contrast enhancement when compared to unlabeled MSCs in a 100 kV CT clinical scanner. The CT signal enhancement from the Bi@US-tubes is 500 times greater than polymer-coated Bi2S3 nanoparticles and several-fold that of any clinical iodinated contrast agent (CA) at the same concentration. Our findings suggest that the Bi@US-tubes can be used as a potential new class of X-ray CT agent for stem cell labeling and possibly in vivo tracking.

The direct ion exchange of chloro(2,6-bis(N-methylbenzimidazol-2-yl)pyridine)platinum(II) ([Pt(Me(2)bzimpy)Cl]+) and chloro(2,2':6',2' '-terpyridine)platinum(II) ([Pt(tpy)Cl]+) complexes within a zirconium phosphate (ZrP) framework has been accomplished. The physical and spectroscopic properties of [Pt(Me(2)bzimpy)Cl]+ and [Pt(tpy)Cl]+ intercalated in ZrP were investigated by X-ray powder diffraction and X-ray photoelectron, infrared, absorption, and luminescence spectroscopies. In contrast to unintercalated complexes in fluid solution, which do not emit at room temperature, both intercalated materials in the solid state and in colloidal suspensions exhibit intense emissions at room temperature. A [Pt(Me(2)bzimpy)Cl]+-exchanged ZrP colloidal methanol suspension gives rise to an emission at 612 nm that originates from a lowest (3)MMLCT[dsigma*(Pt) --> pi*(tpy)] state (MMLCT = metal-metal-to-ligand charge transfer) characteristic of strong Pt...Pt interactions. A [Pt(tpy)Cl]+-exchanged ZrP colloidal aqueous suspension exhibits a strong emission band at 600 nm. The accumulated data demonstrate that at high concentrations, [Pt(Me(2)bzimpy)Cl]+ and [Pt(tpy)Cl]+ ions can serve as luminescent pillars inside the ZrP framework.

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