Nitric Oxide In Solution Research Articles

Solution and solid-state light-induced transformations in heterometallic vanadium-ruthenium nitrosyl complex

The work is devoted to the preparation and photochemical investigations of the novel binuclear heterometallic complex [Ru(NO)(NO2)2(μ-NO2)(μ−CH3COO)(μ-O)VO(dbbpy)]·CH3CN (dbbpy - 4,4′-di-tert-butyl-2,2′-bipyridyl), which is obtained with quantitative yield. The structure of the complex is determined by single crystal X-ray diffraction and by DFT calculations. On the one hand, irradiation at 445 nm of an acetonitrile solution of the complex leads to a NO photo-release reaction. The light excitation induces the charge transfer from NO2 and dbbpy ligands to the antibonding orbitals of ON-Ru-O-V chain, leading to the NO release, which is confirmed by the DFT. The quantum yield of the Ru-NO photo-cleavage is 0.57 ± 0.05 %. The products of the photolysis (NO and paramagnetic RuIII complex) are confirmed by the Griess test and EPR-spectroscopy. On the other hand, the irradiation of the complex in the solid phase at 10 K results in the formation of the metastable bond isomer Ru-ON (MS1), which is detected by the infrared spectroscopy. The stretching vibration of the ν(NO) band of MS1 (1750 cm−1) is shifted by 150 cm−1 to lower energy with respect to the ν(NO) band of the ground state GS (1900 cm−1). The population of the MS1 is about 5%. MS1 thermally decays at 120−140 K back to the GS. Hence, this complex represents a bifunctional platform, which can release nitric oxide in solution and reversibly switch the NO ligand coordination in the solid state. It is shown, that the presence of vanadium strongly influences the photochemical properties of ruthenium nitrosyl both in the solid phase and in solution.

Convenient and selective “off–on” detection nitric oxide in solution and thin film with quinoline based fluorescence sensor

Quinoline based fluorescence sensor (1) was synthesized and characterized with mass spectra (MS), 1H nuclear magnetic resonance (1H NMR) spectrometer, elemental analyses, and infrared (IR) spectra. Following fluorescence experiments demonstrate 1 can coordinate with copper ions, and lead to fluorescence completely quenched. The 1-copper complex was used as a “turn-on” fluorescence biosensor to convenient and highly effective detect nitric oxide (NO) over other radicals in solution and PCL-based thin film. The finding would enable the quinoline based fluorescence probe to be an “off–on” convenient NO fluorescence probe.

Self-activated DNA cleavage and nitric oxide reactivity studies on mononuclear copper complexes derived from tetradentate ligands

Two new tetradentate ligands Timpy (1,2-bis((E)-(2-phenyl-2-(pyridine-2-yl)hydrozono)methyl)benzene) and Gimpy ((1 Z ,2 Z )-1,2-bis(2-phenyl-2-(pyridine-2-yl)hydrozono)ethane) were synthesized and characterized. Mononuclear complexes [Cu(Timpy)(ClO 4 )](ClO 4 ) ( 1 ) and [Cu(Gimpy)](ClO 4 ) 2 ( 2 ) were synthesized and characterized by IR, UV–visible and conductivity measurements. The molecular structure of [Cu(Timpy)(ClO 4 )](ClO 4 ) ( 1 ) was determined by single crystal X-ray diffraction and structural index parameter ( τ = 0.4725) supported distorted square planar geometry at the metal centre. Electrochemical studies for 1 and 2 were investigated. Two-fold applications of these complexes were examined. First, self-activated DNA cleavage activity of complexes 1 and 2 and mechanism of nuclease activity. Second, the complexes were utilized as fluorescence probe for the detection of nitric oxide in solution. Mononuclear copper(II) complexes [Cu(Timpy)(ClO 4 )](ClO 4 ) ( 1 ) and [Cu(Gimpy)](ClO 4 ) 2 ( 2 ) derived from tetradentate ligands Timpy and Gimpy. Two-fold applications of these complexes will be described. First, these complexes were efficient in cleaving DNA in self-activated pathway and enhancement of nuclease activity was observed in presence of oxidizing or reducing agent. Second, the complexes were utilized as fluorescence probe for the detection of nitric oxide. ► Copper complexes derived from tetradentate ligands were synthesized. ► Ligands and complexes were characterized by spectroscopic studies. ► Molecular structure of representative complex was determined by X-ray crystallography. ► Nuclease activity happened via self-activation. ► Nitric oxide detection in solution by fluorescence measurement.

Electrocatalytic reduction of nitric oxide on Pt nanocrystals of different shape in sulfuric acid solutions

Pt tetrahexahedral (Pt-THH) nanocrystals enclosed with 24 { h k 0} facets, Pt nanothorns (Pt-Thorn) with a high surface density of atomic steps, and congeries of Pt nanoparticles (Pt-NP) were prepared and served as catalysts to study the electrocatalytic reduction of both adsorbed and solution nitric oxide. The structure sensitivity for the reduction of a saturated NO adlayer on the Pt nanocrystals (NCs) of different shape was studied by cyclic voltammetry (CV) and in situ FTIR spectroscopy in sulphuric acid solutions. The results revealed that two types of NO adsorbates can be reduced independently at separated potentials, i.e. the reduction of linear bonded NO (NO L) on the Pt-NP electrode gives rise to a current peak at −0.01 V (vs. SCE), while the bridge adsorbed NO (NO B) yields a current peak at −0.08 V. The in situ SNIFTIRS results confirmed the assignment of NO adsorbates, i.e. the NO B species yielding a IR absorption bipolar band with its negative-going peak at 1636 cm −1 and positive-going peak around 1610 cm −1, and the NO L species giving rise to a bipolar band with its negative-going peak at 1809 cm −1 and positive-going peak around 1720 cm −1. It has determined that the NO L species can be preferentially formed on the Pt NCs with open surface structure, i.e. the more open the surface structure of the Pt NCs, the larger the relative quantity of NO L versus NO B. It has also revealed that the Pt NCs with a high surface density of atomic steps exhibit superior electrocatalytic activity for the reduction of solution NO species. The steady-state current density of NO reduction on Pt-THH NCs is 7.5–12 times as large as that on Pt-NP, and that on Pt-Thorn is 2.5–4 times of that on Pt-NP in the reduction potential region of electrochemical dynamic control.

Hybrid Materials from Carbon Nanotubes, Nickel Tetrasulfonated Phthalocyanine and Thin Polymer Layers for the Selective Electrochemical Activation of Nitric Oxide in Solution

AbstractThe elaboration of hybrid materials from single‐wall carbon nanotubes (SWCNT) and tetrasulfonated nickel phthalocyanine (NiTSPc) was electrochemically performed to obtain chemically modified electrodes with improved electrocatalytic activity towards the electrooxidation of nitric oxide (NO). The characterization of these hybrid electrodes was achieved by cyclic voltammetry and AFM. The electrochemical performances of the electrodes towards the oxidation of NO were then analyzed by chronoamperometry and the obtained results show that the presence of SWCNT greatly enhances the electrocatalytic performances in terms of current intensity. Additional coatings were then electrodeposited over the hybrid electrodes to act as selective membranes against four major interfering analytes: nitrite, ascorbate, hydrogen peroxide and L‐arginine. Several polymer coatings were tested to achieve the best balance between sensitivity to NO and selectivity against interferents.

Dual effect of nitric oxide on SARS-CoV replication: Viral RNA production and palmitoylation of the S protein are affected

Nitric oxide is an important molecule playing a key role in a broad range of biological process such as neurotransmission, vasodilatation and immune responses. While the anti-microbiological properties of nitric oxide-derived reactive nitrogen intermediates (RNI) such as peroxynitrite, are known, the mechanism of these effects are as yet poorly studied. Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) belongs to the family Coronaviridae, was first identified during 2002-2003. Mortality in SARS patients ranges from between 6 to 55%. We have previously shown that nitric oxide inhibits the replication cycle of SARS-CoV in vitro by an unknown mechanism. In this study, we have further investigated the mechanism of the inhibition process of nitric oxide against SARS-CoV. We found that peroxynitrite, an intermediate product of nitric oxide in solution formed by the reaction of NO with superoxide, has no effect on the replication cycle of SARS-CoV, suggesting that the inhibition is either directly effected by NO or a derivative other than peroxynitrite. Most interestingly, we found that NO inhibits the replication of SARS-CoV by two distinct mechanisms. Firstly, NO or its derivatives cause a reduction in the palmitoylation of nascently expressed spike (S) protein which affects the fusion between the S protein and its cognate receptor, angiotensin converting enzyme 2. Secondly, NO or its derivatives cause a reduction in viral RNA production in the early steps of viral replication, and this could possibly be due to an effect on one or both of the cysteine proteases encoded in Orf1a of SARS-CoV.

Hybrid Materials from Carbon Nanotubes, Nickel Phthalocyanine, and Polymer Thin Films for the Electrochemical Oxidation of Nitric Oxide in Solution

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Large-scale self-assembly of hydrophilic gold nanoparticles at oil/water interface and their electro-oxidation for nitric oxide in solution

Mono-/bi-layer Au nanoparticle films with large areas were prepared by the assembly of Au nanoparticles in aqueous colloid at toluene/water interfaces, which can be transferred onto the hydrophilic solid surface and adhere strongly to the substrate without any binding agent. The transferred Au nanoparticle films exhibited satisfactory catalytic performance for electro-oxidizing nitric oxide (NO) in solution, and had a low detection limit (2.7 × 10 −8 mol/L), a rapid response time (less than 0.5 s) and a wide linear range (5.0 × 10 −8–1.0 × 10 −5 mol/L) for the detection of NO in solution. UV–vis spectra, cyclic voltammetry and chronoamperometry were conducted to characterize the prepared Au nanoparticle films.

Amperometric fluidic microchip array sensing device for nitric oxide determination in solution

In this paper, we report on the first use of an amperometric fluidic microchip array for the examination of nitric oxide in solution. The array chip is composed of 36 working platinum electrodes on a glass substrate. The electrodes have a diameter of 50 μm and are separated by 500 μm. The array chip is integrated within a flowing cell to obtain a fluidic-type sensing device. Two preliminary tests were performed. The first one consisted in assessing the fluidic set-up by using potassium ferrocyanide as test analyte. The second test was aimed at achieving the modification of the surface of the working electrodes by electrodepositing nickel tetrasulfonated phthalocyanine and Nafion® layers to show that the fluidic sensing device can be adapted to the analysis of nitric oxide in solution.

Electrochemical sensing of nitric oxide for biological systems: methodological approach and new insights in examining interfering compounds

We report here on the appropriate analysis of some examples of interfering compounds that should be done to assess the specificity of the electrochemical sensing of nitric oxide in solution. To do so, we describe the design of a nickel porphyrin and Nafion®-coated carbon microfibre and discuss the methodological approach in examining interfering compounds.

Electrocatalytic Oxidation of Nitric Oxide at 6,17-Diferrocenyl-dibenzo[b,i]5,9,14,18-tetraaza[14]annulen]-nickel(II) Modifed Electrodes

The preparation and electrochemical characterization of glassy carbon, gold or carbon paste electrodes modified with 6,17-Diferrocenyl-dibenzo[b,i]5,9,14,18-tetraaza[14]annulen]-nickel(II) as well as their behavior as electrocatalysts toward the oxidation of nitric oxide is described. These modified electrodes were used for the development of amperometric sensors for the determination of nitric oxide in solution. The sensors were prepared by electrochemical deposition of the mentioned material on glassy carbon or gold electrodes or including it in a carbon paste electrode. The resulting sensors exhibited potent and persistent electrocatalytic activity towards the oxidation of nitric oxide with low detection limits (1 μM) and good linear relationship between the current and nitric oxide concentration.

Detailed methods for the quantification of nitric oxide in aqueous solutions using either an oxygen monitor or EPR

The interest in nitric oxide has grown with the discovery that it has many biological functions. This has heightened the need for methods to quantify nitric oxide. Here we report two separate methods for the quantification of aqueous stock solutions of nitric oxide. The first is a new method based on the reaction of nitric oxide with oxygen in liquid phase (4 NO + O 2 + 2H 2O → 4HNO 2); an oxygen monitor is used to measure the consumption of oxygen by nitric oxide. This method offers the advantages of being both simple and direct. The presence of nitrite or nitrate, frequent contaminants in nitric oxide stock solutions, does not interfere with the quantification of nitric oxide. Measuring the disappearance of dissolved oxygen, a reactant, in the presence of known amounts of nitric oxide has provided verification of the 4:1 stoichiometry of the reaction. The second method uses electron paramagnetic resonance spectroscopy (EPR) and the nitric oxide trap {Fe 2+-(MGD) 2}, (MGD = N-methyl-D-glucamine dithiocarbamate). The nitrosyl complex is stable and easily quantitated as a room temperature aqueous solution. These two methods are validated with Sievers 280 Nitric Oxide Analyzer and cross-checked with standards using UV-Vis spectroscopy. The practical lower limits for measuring the concentration of nitric oxide using the oxygen monitor approach and EPR are approximately 3 μM and 500 nM, respectively. Both methods provide straightforward approaches for the standardization of nitric oxide in solution.

New Composite Modified Carbon Microfibers for Sensitive and Selective Determination of Physiologically Relevant Concentrations of Nitric Oxide in Solution

New Composite Modified Carbon Microfibers for Sensitive and Selective Determination of Physiologically Relevant Concentrations of Nitric Oxide in Solution

New Composite Modified Carbon Microfibers for Sensitive and Selective Determination of Physiologically Relevant Concentrations of Nitric Oxide in Solution

New Composite Modified Carbon Microfibers for Sensitive and Selective Determination of Physiologically Relevant Concentrations of Nitric Oxide in Solution

Improvement in the performance of a nickel complex-based electrochemical sensor for the detection of nitric oxide in solution

The electroformation of the tetrasulfonated nickel phthalocyanine (NiTSPc) film in alkaline solution onto carbon fiber microelectrode is investigated in order to improve the electrochemical detection of nitric oxide (NO) in solution. We compare in this study the sensitivity of a carbon fiber microelectrode coated by nickel phthalocyanine deposited either by cyclic voltammetry or by controlled potential electrolysis at +1.2 V/SCE with a previously reported nickel porphyrin modified electrode. We show that the phthalocyanine film formed by cyclic voltammetry gives a modified microelectrode with a good sensitivity to NO, higher than the obtained one with nickel phthalocyanine and/or porphyrin deposited by controlled potential electrolysis.

A new method for antification of nitric oxide in solution using a standard oxygen monitor

A new method for antification of nitric oxide in solution using a standard oxygen monitor

Direct electrochemical characterization of superoxide anion production and its reactivity toward nitric oxide in solution

We report in this study, and for the first time the direct and simultaneous electrochemical measurements of both nitric oxide and superoxide anion evolution and reactivity in solution. For this purpose, we have combined the use of two electrodes: a previously developed NO-sensor for the amperometric determination of NO and a carbon microelectrode for the amperometric detection of superoxide anion. The latter electrode displayed a potential use for the selective detection of O2− (generated by the xanthine/xanthine oxidase reaction) with an acceptable selectivity against uric acid. Our electrochemical experiments were validated by the Cytochrome c method and by the use of a different procedure for the generation of the superoxide anions. Our results show that the use of the NO sensor provides the selective detection of NO without any interface of the superoxide enzymatic generator.

Electrochemical Detection of Nitric Oxide in Biological Systems

Nitric oxide is a key regulator of diverse physiological processes that include vasoregulation, platelet and neutrophil adherence, and immune defense. The detection and quantification of nitric oxide has been accomplishd by a variety of methodologies. In this paper we desribe methodologies to detect nitric oxide in solution using an electrochemical detector and provide examples of nitric oxide detection in biological systems including data from plasma and cell suspensions. The experiments outlined show that electrochemical detection is suitable for detecting and quantifying nitric oxide within biological samples and buffers. Potential pitfalls and necessary controls are discussed. The use of electrochemical detection was also found to be useful in determining the flux of nitric oxide produced by donor species in different biological buffers.

In SituNitric Oxide (NO) Measurement by Modified Electrodes: NO Labilized by Photolysis of Metal Nitrosyl Complexes

Described are studies directed at refining quantitative analysis of nitric oxide in solution using electrochemical techniques. The fabrication and behavior of several sensors based on modified carbon-based electrodes are reported. This technique has been used to resolve the vexing problem of determining the stoichiometry of the photochemical decomposition of the known antihypertension agent sodium nitroprusside, Na2[Fe(CN)5NO], as well as of two other metal nitrosyl complexes of biological interest, Roussin's black salt, NH4[Fe4S3(NO)7], and Roussin's red salt, Na2[Fe2S2(NO)4], in aqueous solutions. In this manner it was shown that the molar ratios of nitric oxide produced per starting complex photochemically decomposed were 0.95 ± 0.03, 5.9 ± 0.2, and 0.50 ± 0.02 for Na2[Fe(CN)5NO], NH4[Fe4S3(NO)7], and Na2[Fe2S2(NO)4], respectively.

A Search for the Intermediate Radical, ONOO', in the Reaction Between Oxygen and Nitric Oxide in Solution

The most probable initial reaction between NO and O2 is direct addition to give the peroxyl radical ONOO. In view of the potential importance of this radical in biology, we have searched extensively for its formation, using EPR spectroscopy and rapid freezing techniques. At best, only extremely low concentrations were detected, and in most systems, no signals were detectable. We conclude that this radical is unlikely to be of major importance per se in biological systems, in contrast with its one electron adduct, the peroxynitrite anion.