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The performance of various density functional theories (B3LYP, B3PW91, B3P86, B1LYP, BMK, MPWB1K, PBE0, and MPWB95) was examined for calculating N-NO2 bond dissociation energies (BDEs) of 10 N-nitroacylamide compounds. The CBS-4M method was also used. By comparing the calculated results with the experimental values, it was observed that B1LYP/6-31[G.sup.**] and B3LYP/6-31+[G.sup.**] provided accurate BDEs. Especially, B3LYP/6-31+[G.sup.**] was recommended because of its smaller maximum absolute deviation. Further, substituent effects based on the B3LYP/6-31+[G.sup.**] method were analyzed. The result shows that an electron-donating group increases the BDE of the parent [C.sub.6][H.sub.5]-CON(C[H.sub.3]) N[O.sub.2], while an electron-withdrawing group decreases the BDE of the parent [C.sub.6][H.sub.5]-CON (C[H.sub.3])N[O.sub.2]. Subsequently, the BDEs of the other N-nitroacylamindes were estimated. Key words: density functional theory, polarized continuum model, N-nitroacylamides compounds, bond dissociation energy, substituent effects. On a examine les performances relatives de diverses variantes de la theorie de la fonctionnelle de la densite (B3LYP, B3PW91, B3P86, B1LYP, BMK, MPWB1K, PBE0 et MPWB95) pour calculer les energies de dissociation de la liaison (EDL) N-N[O.sub.2] de composes de la famille de 10 N-nitroacylamides. On a aussi fait appel a la methode CBS-4M. Une comparaison des resultats des calculs avec les resultats experimentaux a permis d'observer que les methodes B1LYP/631[G.sup.**] et B3LYP/6-31+[G.sup.**] conduisent aux energies de dissociation de liaison les plus exactes. On recommande particulierement la methode B3LYP/6-31+[G.sup.**] en raison du fait que sa deviation absolue est la plus faible. On a de plus analyse l'effet de substituant par la methode B3LYP/6-31+[G.sup.**]. Les resultats montrent qu'un groupe electrodonneur augmente l'energie de dissociation de la liaison du compose fondamental, [C.sub.6][H.sub.5]-CON(C[H.sub.3])N[O.sub.2], alors qu'un groupe electroattracteur la diminue. Finalement, on a aussi evalue les energies de dissociation de liaison d'autres N-nitroacylamides. Mots-cles : theorie de la fonctionnelle de la densite, modele du continuum polarise, composes de la famille des N-nitroacylamides, energie de dissociation de la liaison, effets de substituant., Introduction Nitric oxide (NO) is a free-radical gas and one of the smallest known biologically active messenger molecules, which plays key roles in regulating a diverse range of physiological processes, [...]

α, β-Unsaturated arylhydrazones (1) reacted with nitric oxide (NO) in the presence of a trace of oxygen to give a(2a-2c, 2e, and 2f)or β-nitro (2d and 2g) unsaturated hydrazones in good yield and with high stereoselectivity. The reaction occurs most likely by an electrophilic addition of N[O.sub.2] to the carbon-carbon double bond of 1 at its α-or β-position. Key words: α,β-unsaturated hydrazone, nitric oxide, nitration reaction, electrophilic addition. Les arylhydrazones α,β-insaturees (1) reagissent avec l'oxyde nitrique (NO), en presence d'une trace d'oxygene pour conduire a la formation d'a-(2a-2c, 2e et 2f)oude β-nitrohydrazones (2d et 2g) insaturees, avec des bons rendements et une grande stereoselectivite. La reaction se produit tres probablement par une addition electrophile de N[O.sub.2] sur les positions α ou β de la double liaison carbone-carbone du compose 1. Mots-cles : hydrazone α,β-insaturee, oxyde nitrique, reaction de nitration, addition electrophile., Introduction Studies on nitric oxide (NO) associated with life processes have attracted more attention from scientists. The proper regulation of NO levels has been proposed as a desirable target for [...]

A novel method is proposed to measure NO in breath. Breath NO is a useful diagnostic measure for asthma patients. Due to the low water solubility of NO, existing wet chemical NO measurements are conducted on N[O.sub.2] after removal of pre-existing N[O.sub.2] and conversion of NO to N[O.sub.2]. In contrast, this study utilizes direct measurement of NO by wet chemistry. Gaseous NO was collected into an aqueous phase by a honeycombpatterned microchannel scrubber and reacted with diaminofluorescein-2 (DAF-2). Fluorescence of the product was measured using a miniature detector, comprising a blue light-emitting diode (LED) and a photodiode. The response intensity was found to dramatically increase following addition of N[O.sub.2] into the absorbing solution or air sample. By optimizing the conditions, the sensitivity obtained was sufficient to measure parts per billion by volume levels of NO continuously. The system was applied to real analysis of NO in breath, and the effect of coexisting compounds was investigated. The proposed system could successfully measure breath NO.

Computer simulation methods are used for studying the nitric oxide (NO) release mechanism of nitrophorin 4 (NP4) at a molecular level. The results have shown that NP4 has evolved a cage mechanism that has trapped the NO at low pH and has released it upon cage opening when the pH has increased.

Contrary to many reports, sodium methoxide is shown to react with nitric oxide (NO). Sodium trimethylsilanoate is considered as a substitute for sodium methoxide as the base used to achieve the replacement of active hydrogens by the diazeniumdiolate functional group via the Traube reaction.

Nitric oxide (NO) is increasingly being used in the medical treatments of high blood pressure, acute respiratory distress syndrome, and some illnesses related to the lung. A convenient and safe production and operation system of NO is of interest to the medical circle. In this paper, NO was produced using pulsed discharge between needle-plate electrodes made of different materials in dry air under latin. The effects of varying the distance between electrodes, the pulsed discharge repetition frequency, the flow rate of clean air and the reactor operation time on the concentrations of NO and N[O.sub.2], and the ratio of N[O.sub.2]/NO are presented. The method of removing N[O.sub.2] is also introduced in detail. The results of the experiment show that on the cure of N[O.sub.2]/NO versus the distance between electrodes, a minimum ratio of about 7.8% has appeared at the distance of 3.5 mm. The concentrations of NO and N[O.sub.2] are increased with increasing the pulsed discharge repetition frequency and decreased with an increase in the air flow rate. The small quantity of toxic N[O.sub.2] could be deoxidized through catalytic process to NO which can be used in treatment. The ratio of N[O.sub.2]/NO decreased to a value below 3% when the gas temperature for deoxidization reached 790 K. Concurrently, the stable concentration of NO could be acquired through a pulsed arc discharge in dry air. Index Terms--Acute respiratory distress syndrome (ARDS), inhaled nitric oxide (iNO), molybdenum (Mo), pulsed discharge.

Interest in elucidating the mechanisms of action of various classes of anticancer agents and exploring the pathways of the induced-nitric oxide (NO) release provides an impetus to conceive a better designed approach to locally detect NO in tumors, in vivo. We report here on the first use of an electrochemical sensor that allows the in vivo detection of NO in tumor-bearing mice. In a first step, we performed the electrochemical characterization of a stable electroactive probe, [K.sup.4]Fe[(CN).sup.6], directly injected into the liquid microenvironment especially created around the electrode in the tumor. Second, the ability of the inserted electrode system to detect the presence of NO itself in the tumoral tissue was achieved by using the chemically modified Pt/Ir electrode as NO sensor and two NO donor molecules: diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium 1,2-diolate (DEA-NONOate) and (Z)-1-[N-(2-aminopropyl)-N-(2-ammonio propyl)amino]diazen-1-ium 1,2-diolate (PAPA-NONOate). These two NO donor molecules allowed proving the electrochemical detection of (i) directly injected exogenous NO phosphate buffer solution into the tumor (decomposed DEA-NONOate) and (ii) biomimetically induced endogeneous release of NO in the tumoral tissue, upon injection of PAPA-NONOate into the tumor. This approach could be applied to the in vivo study of candidate anticancer drugs acting on the NO pathways.

Nitric oxide (NO) triggers various physiological responses in numerous tissues by binding and activating soluble guanylate cyclase (sGC) to produce the second messenger cGMP. In vivo, basal NO/cGMP signaling maintains a resting state in target cells (for example, resting tone in smooth muscle), but an acute burst of NO/cGMP signaling triggers rapid responses (such as smooth muscle relaxation). Recent studies have shown that the sGC heterodimer comprises at least four modular domains per subunit. The N-terminal heme domain is a member of the H-NOX family of domains that bind [O.sub.2] and/or NO and are conserved in prokaryotes and higher eukaryotes. Studies of these domains have uncovered the molecular basis for ligand discrimination by sGC. Other work has identified two temporally distinct states of sGC activation by NO: formation of a stable NO-heme complex results in a low-activity species, and additional NO produces a transient fully active enzyme. Nucleotides also allosterically modulate the duration and intensity of enzyme activity. Together, these studies suggest a biochemical basis for the two distinct types of NO/cGMP signal observed in vivo.

The potential physiological relevance of myeloperoxidase (MPO)-nitric oxide (NO) interactions was examined as it relates to cosubstrate, pseudo halide thiocyanate (SCN(super -)), and substrate switching. It reveals that (patho)pysiologically relevant levels of NO have significant effects on MPO compound II accumulation.

Dysregulation of nitric oxide (NO) and increased oxidative and nitrosative stress are implicated in the pathogenesis of heart failure. Peroxynitrite is a reactive oxidant that is produced from the reaction of nitric oxide with superoxide anion and impairs cardiovascular function through multiple mechanisms, including activation of matrix metalloproteinases (MMPs) and nuclear enzyme poly(ADP-ribose) polymerase (PARP). Recent studies suggest that the neutralization of peroxynitrite or pharmacological inhibition of MMPs and PARP are promising new approaches in the experimental therapy of various forms of myocardial injury. In this article, the role of nitrosative stress and downstream mechanisms, including activation of MMPs and PARP, in various forms of heart failure are discussed and novel emerging therapeutic strategies offered by neutralization of peroxynitrite and inhibition of MNIPs and PARP in these pathophysiological conditions are reviewed.

The molecular basis of the NO interaction with Alcaligenes xylosoxidans (AXCP) is explored by using hybrid classical simulation techniques. The results suggest that Fe-His bond breaking depends not only on the iron-histidine bond strength but also on the existence of a local minimum conformation of the protein with the histidine away from the iron.

A combined, optospectroscopic and electrochemical assay system for the simultaneous monitoring of intra- and extracellular production of biologically important species has been developed and assessed. The present model system evaluates intra- and extracellular nitric oxide produced by stimulated glioblastoma multiform cell line (A172). The production of endogenous NO was induced by phorbol-12-myristate-13-acetate and inhibited by [N.sup.[omega]]-nitro-L-arginine methyl ester. Intracellular production of NO was monitored via fluorescence image analysis using a 4,5-diaminofluorescein probe, while extracellular NO release was monitored via a chemically modified electrode, which was incorporated into an optically transparent cell chip. The results indicated that there was no mutual interference between the optical and electrochemical measurement systems. The response time of the combined optical/electrochemical system was found to be in the range of a few tens of seconds.

Ammonia radicals are produced by a dielectric barrier discharge (DBD) in a chamber separate from the chamber that NO gas flows, and are injected in the NO gas flowing field to decompose NO gas. The power source for generating the DBD is a one-cycle sinusoidal (OCS) waveform so as to easily control the power consumed in the DBD plasma. The fundamental frequency of the OCS power source is 150 kHz. The correlation of the DeNOx characteristics was discussed, where the residence time of the ammonia gas in the radical injector and the power density consumed in the DBD plasma were considered. Their product was called residence energy density (RED). It was confirmed that the parametric data of the DeNOx energy efficiency were clearly correlated by the RED. Currently, the energy efficiency of 250 g/kWh was attained at a NO gas temperature of 600 [degrees]C. In order to obtain a high-energy efficiency in this system, the suppression of the energy consumed in the DBD plasma is effective, and instead, the ammonia flow rate decreases, compensating the accepted energy of the ammonia particles by the residence in the radical injector. Index Terms--Dielectric barrier discharge, intermittent discharge, NOx removal, nonthermal plasma.

The induced isoform of nitric oxide synthase (iNOS) and three zinc tetrathiolate mutants were expressed in Escherichia coli and purified. The data show that S-nitrosation of the zinc tetrathiolate cysteine results in zinc release from the dimer interface and formation of inactive monomers, suggesting that this mode of inhibition might occur in vivo.

The interaction of nitric oxide with cytochrome P450 BM3 from Bacillus megaterium is analyzed by spectroscopic techniques and enzyme assays in order to identify nitrated tyrosine residue(s) in the enzyme. Nitric oxide ligates tightly to the ferric heme iron, inducing large changes in each of the main visible bands of the heme and inhibiting the fatty acid hydroxylase function of the protein.

Two ruthenium(II) porphyrin complexes bearing axial ligand fluorophores were synthesized and investigated for their ability to detect nitric oxide with turn-on emission.

Two main hypotheses describe the role of hemoglobin in the regulation of nitric oxide (NO) bioavailability. It has been suggested that hemoglobin interacts with circulating NO, forming Fe-nitrosvI hemoglobin and then S-nitrosothiols, which deliver NO extracellularly by an allosterically regulated mechanism. Alternatively, the existence of diffusional barriers that protect NO from hemoglobin-mediated degradation has been proposed. The reliability of each model in vivo is supported by the detection of physiological hematic levels of S-nitrosohemoglobin. However, the measured concentrations of S-nitrosohemoglobin are largely divergent between the two models. Moreover, recent reports suggest that circulating levels of S-nitrosohemoglobin in human blood could be significantly lower than assessed previously. We suggest that solving the methodological controversies that make the field of NO research a 'minefield', even for skilled analysts, is fundamental to understanding the role of S-nitrosothiols in the vasculature.

Nitric oxide generation from porcine kidney slices is assessed using a new planar NO-selective amperometric sensor. The planar shape of the sensor allows for direct NO measurements near the surface (10 [micro]m) of renal tissue slices in real time. Renal NO production may be modulated by the addition of L-arginine, arginine homopolymers (R2, R6, R10), and protamine, all of which can potentially transport across cellular membranes and provide a substrate for nitric oxide synthase within kidney parenchyma. Real-time amperometric measurements demonstrate that most L-arginine species can translocate across the cell membrane and rapidly increase NO production. However, no increase in NO generation is observed when the dimer of L-arginine (R2) is added to the solution bathing the tissue, suggesting that this species cannot permeate cell membranes. The degree of enhancement in NO generation observed for L-arginine and the larger peptides depends on the structure and follows the following sequence: R10 (decamer) > protamine > R6 (hexamer) > L-arginine. Protamine and the R10 decamer, especially, induce the largest increases in NO generation owing to their apparent rapid translocation into cells and subsequent cleavage by proteases to create high intracellular levels of L-arginine. The effect of sensor size (for sensor dimensions of 0.15- and 1-mm outer diameters) on the measured surface NO levels is also examined. The larger sensor traps more NO but hinders access of the L-arginine species to the tissue area between the flat distal plane of the sensor and the surface of the kidney slice. The use of such NO-generating peptides may be important in numerous biological systems that depend on NO production, such as ischemia-reperfusion injury and thrombogenesis.

An improved miniature amperometric nitric oxide sensor design with a planar sensing tip (ranging from 150 [micro]m to 2 mm in diameter) is reported. The sensor is fabricated using a platinized platinum anode and a Ag/AgCl cathode housed behind a microporous poly(tetrafluoroethylene) (PTFE; Gore-tex) gas-permeable membrane. Platinization of the working platinum electrode surface dramatically improves the analytical performance of the sensor by providing ~10-fold higher sensitivity (0.8-1.3 pA/nM), ~10-fold lower detection limit ([less than or equal to] 1 nM), and extended (at least 3-fold) stability (>3 d) compared to sensors prepared with bare Pt electrodes. These improvements in performance arise from increasing the kinetics and lowering the required potential for the 3-electron oxidation of NO to nitrate, relative to that observed using a nonplatinized working electrode. The outer porous PTFE membrane provides complete selectivity for NO over nitrite ions (up to 10 mM nitrite). The new sensor is applied for surface measurements of NO released from diazeniumdiolate-loaded silicone rubber films (SR-DACA-6/[N.sub.2][O.sub.2]). The effects of sensor size (for sensor dimensions of 0.15-, 1-, and 2-mm o.d.) and the distance of the sensor from the surface of the NO-emitting polymer film are investigated via experiments as well as theoretical calculations. A significant analyte trapping effect is demonstrated, the degree of which depends on the sensor size and its distance from the surface. It is further demonstrated that surface NO concentrations for fresh SR-DACA-6/[N.sub.2][O.sub.2] loaded films are also influenced by the polymer film thickness, with thicker films generating higher surface concentrations of NO.

An investigation into the system of isolating several Lewis-base adducts of the acidic Fe(NO)(sub 3)(super +) species disclosed that they exhibit distinctly bent Fe-N-O linkages. Experiments carried out show that the bending of the NO ligands results in an increase in the energy of the HOMO relative to the linear case, but at the same time causes a decrease in energy of the HOMO-1 and the HOMO-2 molecular orbitals.

Studies undertaken in the past six years have shown that nitric oxide and many members of the sphingolipid family interact in two-way systems, whereby each 'player' regulates and is regulated by another 'player'. These interactions take place at the level of the expression and activity of several enzymes that regulate both the sphingolipid metabolic pathways and the generation of nitric oxide. So far, the outcomes of these interactions have been elucidated only in part. It is already clear, however, that they play prominent roles in key biological processes, including apoptosis, inflammation and cell growth.

Nitric oxide production is stimulated by an increase of the concentration of cytosolic [Ca.sup.2+] in vascular endothelial cells. Recent evidence suggests that nitric oxide and cGMP might attenuate [Ca.sup.2+] influx and, at the same time, initiate a [Ca.sup.2+] removal mechanism, thereby decreasing the intracellular concentration of endothelial [Ca.sup.2+] in a negative feedback fashion. Such a negative feedback mechanism could serve to protect the endothelial cells from the detrimental effects of excessive nitric oxide and [Ca.sup.2+].

The synthesis and NO-release characteristics of a number of different N-diazeniumdiolate-functionalized fumed silica particles are presented. The use of NO-releasing particles is explored in biomedical/pharmaceutical/cosmetic applications.

The IR spectroscopy is use to investigate the interactions of nitric oxide gas with thin layers of Fe(super ll)(TPP) and Ru(super ll)(TPP), obtained by sublimation onto low-temperature substrate (77 K). It was found that purified nitrogen oxide does not react with Fe(TPP)(NO) to give Fe(TPP)(NO)(NO2), however, this interaction led only to the formation of unstable trans-dinitrosyl complex Fe(TPP)-(NO)2.

Computational methods, including density functionals and single and multi reference ab initio methods, were used in investigations into the tautomerism of furoxan.

Research has been conducted on nitric oxide (NO) which acts as a ligand for molecular oxygen at the cytochrome c oxidase active site. The results of the flash photolysis studies of NO from heme (sub)3 via femtosecond transient absorption spectroscopy are presented.

Diazeniumdiolate chemistry is examined in terms of kinetics and mechanism of nitric oxide dissociation in aqueous solution.

Research has been conducted on the ferric heme-nitric oxide (NO) complex. The kinetics of its formation, dependence on NO concentration solution, and effects on enzyme oxygen response and catalytic activity have been investigated.

The structure of nitric oxide synthase complexed with two inhibitors is described. The inhibitors are N(super 5)-(1-iminoethyl)-L-ornithine and N-(3-(aminomethyl)benzyl)acetamide.

Calcium regulates the activity of tissue transglutaminase, which is an enzyme that cross-links proteins involved in wound healing and tissue remodeling. Calcium stimulates the nitrosylation and denitrosylation of the enzyme and protects the enzyme from inhibition by Mg-GTP.

Evidence of an N-N-coupled intermediate gerenarted from reactimg NO-Fe(TPP) with NO and capable of O atom transfer reactions is presented.

The development of a new polymer material that reversibly binds nitric oxide is reported.

Independent studies from three laboratories of the hydrostatic and temperature pressure effects on the reaction of metmyoglobin with nitric oxide are described.

P-nitrosophosphates represent new asymmetric N-O heterodienophiles that react with 1,3-dienes to produce complex oxygen-, nitrogen-, and phosphorous- containing cycloadducts and permit the direct introduction of the phosphoramidate functional group. P-nitrosophosphates also reacts with water to yield nitoxyl, the biologically important one-electron-reduced form of nitric oxide.

There are two mechanisms that regulate the two successive monooxygenase reactions from L-arginine and L-citrulline in rat neuronal nitric oxide synthase. One control the rate of the monooxygenation and the other controls the amount of the active enzyme.

Nitric Oxide plays an important role in many striking discoveries of wide human physiological processes. Experiments conducted on four substituted derivatives of Hantzsch 1,4 dihydropyridines were treated by nitric oxide (NO) or its donor N-methyl-N-nitrosotoluene-p-sulfonamide (MNTS) to give the corresponding pyridine derivatives and its results are discussed.

The binding kinetics of three different heme ligands to endothelial nitric oxide synthase is described. A P450 reductase domain is attached to an oxygenase domain, where the catalytic site is located.

Research has been conducted on the alpha-amino acids that bear a C=NOH function. Results indicate that these acids have been tested as substrates of recombinant nitric oxide synthases I and II.

Research has been conducted on the nitric oxide. The use of unilamellar liposomes in investigating the nitric oxide inhibition of propagative lipid peroxidation is discussed.

Studies have indicated that nitric oxide (NO) prohibits the cytochrome P450 enzyme. Density functional theory and the SAMI semiempirical methods were used to study the interaction between Nitric Oxide (NO) and the active site of the enzyme.

The compound, [RuCl(NO)(cyclam)](super 2+), releases chloride quickly and then NO more slowly on reduction. Due to slow disassociation, the complex is promising as a controlled-release NO prodrug for vasodilation over relatively long periods but not sufficiently fast to affect neuronal firing in hippocampal slices.

Research has been conducted on the nitric oxide synthases. The catalysis of the heme-based oxidations to N (super)omega-hydroxy-L-arginine and then to L-citrulline and nitric oxide is described.

A nitric oxide detection strategy was successfully implemented using metalloporphyrin-mediated effects on the PL of CdSe substrates.

Research has been conducted on the FixL heme domain. The structures of Bradyrhizobium japonicum FixL heme domain bound to dioxygen, imidazole and nitric oxide have been identified.

The development and in vivo analytical performance of a nitric oxide (NO)-releasing amperometric oxygen sensor with greatly enhanced thromboresistivity are reported. Gas permeable coatings formulated with cross-linked silicone rubber (SR) containing NO-generating compounds (diazeniumdiolates) are shown to release NO for extended periods of time (> 20 h) while reducing platelet adhesion and activation. Oxygen-sensing catheters prepared by dip-coating the NO-releasing films over the outer SR tubes of the implantable devices display similar analytical response properties in vitro (sensitivity, selectivity, response times) when compared to analogous sensors prepared without the NO release coatings. Superior analytical accuracy (relative to blood PO(sub 2) values measured in vitro) and greatly reduced thrombus formation on the outer surface of the sensors are observed in vivo (in canine model) with the NO release PO(sub 2) sensors compared to control sensors (without NO release) implanted simultaneously within the same animals. Based on these preliminary studies, the use of NO release polymers to fabricate catheter-style chemical sensors may be a potential solution to lingering biocompatibility and concomitant performance problems encountered when attempting to employ such devices for continuous intravascular measurements of blood gases and electrolytes.

Researchers describe the steps in the reaction of nitric oxide synthase with N-hydroxy-L-arginine (NOHA) or L-arginine using the oxygenase domain of the enzyme. The reaction involves a ferrous-dioxy enzyme, which reacts with NOHA to form a ferric heme-NO complex.

Research has been conducted on the oxidative stress in biological membranes. Results indicate that nitric oxide donor PAPANONOate protects all phospholipids from oxidation in HL-60 cells.

Research has been conducted on the radical nitric oxide reaction with W(phen)(CO) (sub)2 (SPh) (sub)2. Reduction of W(II) bisthiolates to W(0) nitrosyl thiolate is examined.

Research has been conducted on the reaction of H-Cr(CO) (sub)3 C (sub)5 Me (sub)5 with radicalNO. Decomposition of the initial product HNO has been described.

A study of the thermodynamic properties of the flavin cofactors in neuronal nitric oxide synthase in the calmodulin-free and -bound forms is presented. Results demonstrate that flavins can exist with a stable blue semiquinone.