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Nitrite uptake into red blood cells (RBCs) precedes its intracellular reactions with hemoglobin (Hb) that forms nitric oxide (NO) during hypoxia. We investigated the uptake of nitrite and its reactions with Hb at different oxygen saturations (S[O.sub.2]), using RBCs with (carp and rabbit) and without (hagfish and lamprey) anion exchanger-1 (AE1) in the membrane, with the aim to unravel the mechanisms and oxygenation dependencies of nitrite transport. Added nitrite rapidly diffused into the RBCs until equilibrium. The distribution ratio of nitrite across the membrane agreed with that expected from HN[O.sub.2] diffusion and AEI-mediated facilitated NO2 diffusion. Participation of HN[O.sub.2] diffusion was emphasized by rapid transmembrane nitrite equilibration also in the natural AE1 knockouts. Following the equilibration, nitrite was consumed by reacting with Hb, which created a continued inward diffusion controlled by intracellular reaction rates. Changes in nitrite uptake with S[O.sub.2], pH, or species were accordingly explained by corresponding changes in reaction rates. In carp, nitrite uptake rates increased linearly with decreasing S[O.sub.2] over the entire S[O.sub.2] range. In rabbit, nitrite uptake rates were highest at intermediate S[O.sub.2], producing a bell-shaped relationship with S[O.sub.2]. Nitrite consumption increased ~10-fold with a 1 unit decrease in pH, as expected from the involvement of protons in the reactions with Hb. The reaction of nitrite with deoxyhemoglobin was favored over that with oxyhemoglobin at intermediate S[O.sub.2]. We propose a model for RBC nitrite uptake that involves both HN[O.sub.2] diffusion and AE1-mediated transport and that explains both the present and previous (sometimes puzzling) results. anion exchanger-l; facilitated diffusion; HN[O.sub.2] diffusion; nitric oxide doi: 10.1152/ajpregu.00813.2009.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.forsciint.2009.10.011 Byline: Asya Vinokurov (a), Avraham Zelkowicz (a), Ehud (Udi) Wolf (a), Arie Zeichner (b) Keywords: Forensic science; Shooting distance; Gunpowder residue; Total nitrite; FDR; Contamination Abstract: A study was conducted to assess the influence of a possible contamination of the victim's clothing by gunpowder residue on the estimation of shooting distance. The study was focused on the scenario in which the contamination might be caused by the surface on which the shot victim could fall. Contamination of two types of textile was examined after contact with two types of surfaces. One round was fired above those surfaces (the line of firing parallel to the surface) prior to the contact. It was found that few gunpowder residue particles could be transferred to the clothing. These findings should be taken into account when interpreting results for shooting distance estimation in cases when a minute quantity of gunpowder residue particles is found around the bullet entrance hole. Author Affiliation: (a) Division of Identification and Forensic Science (DIFS), Israel Police National Headquarters, Jerusalem 91906, Israel (b) Forensic Science Consultant, Nof Harim 19 B, Jerusalem 96190, Israel Article History: Received 2 June 2009; Revised 30 September 2009; Accepted 9 October 2009

Aamand R, Dalsgaard T, Jensen FB, Simonsen U, Roepstorff A, Fago A. Generation of nitric oxide from nitrite by carbonic anhydrase: a possible link between metabolic activity and vasodilation. Am J Physiol Heart Circ Physiol 297: H2068-H2074, 2009. First published October 9, 2009; doi: 10.1152/ajpheart.00525.2009.--In catalyzing the reversible hydration of C[O.sub.2] to bicarbonate and protons, the ubiquitous enzyme carbonic anhydrase (CA) plays a crucial role in C[O.sub.2] transport, in acid-base balance, and in linking local acidosis to [O.sub.2] unloading from hemoglobin. Considering the structural similarity between bicarbonate and nitrite, we hypothesized that CA uses nitrite as a substrate to produce the potent vasodilator nitric oxide (NO) to increase local blood flow to metabolically active tissues. Here we show that CA readily reacts with nitrite to generate NO, particularly at low pH, and that the NO produced in the reaction induces vasodilation in aortic rings. This reaction occurs under normoxic and hypoxic conditions and in various tissues at physiological levels of CA and nitrite. Furthermore, two specific inhibitors of the C[O.sub.2] hydration, dorzolamide and acetazolamide, increase the CA-catalyzed production of vasoactive NO from nitrite. This enhancing effect may explain the known vasodilating effects of these drugs and indicates that C[O.sub.2] and nitrite bind differently to the enzyme active site. Kinetic analyses show a higher reaction rate at high pH, suggesting that anionic nitrite participates more effectively in catalysis. Taken together, our results reveal a novel nitrous anhydrase enzymatic activity of CA that would function to link the in vivo main end products of energy metabolism (C[O.sub.2]/[H.sup.+]) to the generation of vasoactive NO. The CA-mediated NO production may be important to the correlation between blood flow and metabolic activity in tissues, as occurring for instance in active areas of the brain. acetazolamide; dorzolamide; acidosis; neurovascular coupling doi: 10.1152/ajpheart.00525.2009

The nitrite anion is an endogenous product of mammalian nitric oxide (NO) metabolism, a key intermediate in the nitrogen cycle in plants, and a constituent of many foods. Research over the past 6 years has revealed surprising biological and cytoprotective activity of this anion. Hypercholesterolemia causes a proinflammatory phenotype in the microcirculation. This phenotype appears to result from a decline in NO bioavailability that results from a reduction in NO biosynthesis, inactivation of NO by superoxide, or both. Since nitrite has been shown to be potently cytoprotective and restore NO biochemical homeostasis, we investigated if supplemental nitrite could attenuate microvascular inflammation caused by a high cholesterol diet. C57Bl/6J mice were fed either a normal diet or a high cholesterol diet for 3 wk to induce microvascular inflammation. Mice on the high cholesterol diet received either nitrite-free drinking water or supplemental nitrite at 33 or 99 mg/l ad libitum in their drinking water. The results from this investigation reveal that mice fed a cholesterol-enriched diet exhibited significantly elevated leukocyte adhesion to and emigration through the venular endothelium as well as impaired endothelium-dependent relaxation in arterioles. Administration of nitrite in the drinking water inhibited the leukocyte adhesion and emigration and prevented the arteriolar dysfunction. This was associated with sparing of reduced tetrahydrobiopterin and decreased levels of C-reactive protein. These data reveal novel anti-inflammatory properties of nitrite and implicate the use of nitrite as a new natural therapy for microvascular inflammation and endothelial dysfunction associated with hypercholesterolemia. nitrosothiols; tetrahydrobiopterin; C-reactive protein; leukocyte adhesion

Allosteric regulation of nitrite reduction by deoxyhemoglobin has been proposed to mediate nitric oxide (NO) formation during hypoxia. Nitrite is predominantly an anion at physiological pH, raising questions about the mechanism by which it enters the red blood cell (RBC) and whether this is regulated and coupled to deoxyhemoglobin-mediated reduction. We tested the hypothesis that nitrite transport by RBCs is regulated by fractional saturation. Using human RBCs, nitrite consumption was faster at lower fractional saturations, consistent with faster reactions with deoxyheme. A membrane-based regulation was suggested by slower nitrite consumption with intact versus lysed RBCs. Interestingly, upon nitrite addition, intracellular nitrite concentrations attained a steady state that, despite increased rates of consumption, did not change with decreasing oxygen tensions, suggesting a deoxygenation-sensitive step that either increases nitrite import or decreases the rate of nitrite export. A role for anion exchanger (AE)-I in the control of nitrite export was suggested by increased intracellular nitrite concentrations in RBCs treated with DIDS. Moreover, deoxygenation decreased steady-state levels of intracellular nitrite in AE-l-inhibited RBCs. Based on these data, we propose a model in which deoxyhemoglobin binding to AE-I inhibits nitrite export under low oxygen tensions allowing for the coupling between deoxygenation and nitrite reduction to NO along the arterial-to-venous gradient. oxygen; anion exchanger-I; hypoxic vasodilation

Nitrate-dependent Fe(II) oxidation is an important process in the inhibition of soil Fe(III) reduction, yet the mechanisms are poorly understood. One proposed pathway includes chemical reoxidation of mineral forms of Fe(II) such as siderite [FeC[O.sub.3[s)]] by N[O.sub.2.sup.-]. Accordingly, the objective of this study was to investigate the reactivity of FeC[O.sub.3(s)] with N[O.sub.2.sup.-]. Stirred-batch reactions were performed in an anoxic chamber across a range of pH values (5.5, 6, 6.5, and 7.9), initial FeC[O.sub.3(s)] concentrations (5, 10, and 15 g [L.sup.-1]) and initial N[O.sub.2.sup.-] concentrations (0.83-9.3 mmol [L.sup.-1]) for kinetic and stoichiometric determinations. Solid-phase products were characterized using x-ray diffraction (XRD). Siderite abiotically reduced N[O.sub.2.sup.-] to [N.sub.2]O. During the process, FeC[O.sub.3(s)] was oxidized to lepidocrocite [[gamma]-FeOO[H.sub.(s)]] based on the appearance of XRD peaks located at 0.624, 0.329, and 0.247 nm. The rate of N[O.sub.2]-reduction was first order in total N[O.sub.2.sup.-] concentration and FeC[O.sub.3(s)], with a second-order rate coefficient (k) of 0.55 [+ or -] 0.05 [M.sup.-1] [h.sup.-1] at pH 5.5 and 25[degrees]C. The reaction was proton assisted and k values increased threefold as pH decreased from 7.9 to 5.5. The influence of pH on N[O.sub.2.sup.-] reduction was rationalized in terms of the availability of FeC[O.sub.3(s)] surface sites (>FeHC[O.sub.3.sup.0], >FeO[H.sub.2.sup.+], and >C[O.sub.3][Fe.sup.+]) and HN[O.sub.2] concentration. These findings indicate that if FeC[O.sub.3](s) is present in an Fe(III)-reducing soil where fertilizer N[O.sub.3.sub.-] is applied, it can participate in secondary chemical reactions with N[O.sub.2.sup.-] and lead to an inhibition in Fe(III) reduction. This process is relevant in soil environments where N[O.sub.3.sup.-] - and Fe(III)-reducing zones overlap or across aerobic-anaerobic interfaces. Abbreviations: XRD, x-ray diffraction.

Successful pathogens must be able to protect themselves against reactive nitrogen species generated either as part of host defense mechanisms or as products of their own metabolism. The regulatory protein NsrR (a member of the Rrf2 family of transcription factors) plays key roles in this stress response. Microarray analysis revealed that NsrR represses nine operons encoding 20 genes in Escherichia coli MG1655, including the hmpA, ytfE, and ygbA genes that were previously shown to be regulated by NsrR. Novel NsrR targets revealed by this study include hcp-hcr (which were predicted in a recent bioinformatic study to be NsrR regulated) and the well-studied nrfA promoter that directs the expression of the periplasmic respiratory nitrite reductase. Conversely, transcription from the ydbC promoter is strongly activated by NsrR. Regulation of the nrf operon by NsrR is consistent with the ability of the periplasmic nitrite reductase to reduce nitric oxide and hence protect against reactive nitrogen species. Gel retardation assays were used to show that both FNR and NarL bind to the hop promoter. The expression of hcp and the contiguous gene hcr is not induced by hydroxylamine. As hmpA and ytfE encode a nitric oxide reductase and a.mechanism to repair iron-sulfur centers damaged by nitric oxide, the demonstration that hcp-hcr, hmpA, and ytfE are the three transcripts most tightly regulated by NsrR highlights the possibility that the hybrid cluster protein, HCP, might also be part of a defense mechanism against reactive nitrogen stress.

Nitrite is a central intermediate in the nitrogen cycle and can persist in significant concentrations in ocean waters, sediment pore waters, and terrestrial groundwaters. To fully interpret the effect of microbial processes on nitrate (N[O.sub.3.sup.-]), nitrite (N[O.sub.2.sup.-]), and nitrous oxide ([N.sub.2]O) cycling in these systems, the nitrite pool must be accessible to isotopic analysis. Furthermore, because nitrite interferes with most methods of nitrate isotopic analysis, accurate isotopic analysis of nitrite is essential for correct measurement of nitrate isotopes in a sample that contains nitrite. In this study, nitrite salts with varying oxygen isotopic compositions were prepared and calibrated and then used to test the denitrifier method for nitrite oxygen isotopic analysis. The oxygen isotopic fracfionation during nitrite reduction to [N.sub.2]O by Pseudomonas aureofaeiens was lower than for nitrate conversion to [N.sub.2]O, while oxygen isotopic exchange between nitrite and water during the reaction was similar. These results enable the extension of the denitrifier method to oxygen isotopic analysis of nitrite (in the absence of nitrate) and correction of nitrate isotopes for the presence of nitrite in 'mixed' samples. We tested storage conditions for seawater and freshwater samples that contain nitrite and provide recommendations for accurate oxygen isotopic analysis of nitrite by any method. Finally, we report preliminary results on the equilibrium isotope effect between nitrite and water, which can play an important role in determining the oxygen isotopic value of nitrite where equilibration with water is significant.

Accumulating evidence suggests that the simple and ubiquitous anion salt, nitrite (N[O.sub.2.sup.-]), is a physiological signaling molecule with potential roles in intravascular endocrine nitric oxide (NO) transport, hypoxic vasodilation, signaling, and cytoprotection after ischemia-reperfusion. Human and animal studies of nitrite treatment and NO gas inhalation provide evidence that nitrite mediates many of the systemic therapeutic effects of NO gas inhalation, including peripheral vasodilation and prevention of ischemia-reperfusion-mediated tissue infarction. With regard to nitrite-dependent hypoxic signaling, biochemical and physiological studies suggest that hemoglobin possesses an allosterically regulated nitrite reductase activity that reduces nitrite to NO along the physiological oxygen gradient, potentially contributing to hypoxic vasodilation. An expanded consideration of nitrite as a hypoxiadependent intrinsic signaling molecule has opened up a new field of research and therapeutic opportunities for diseases associated with regional hypoxia and vasoconstriction. hemoglobin; hypoxia; S-nitrosated albumin; cysteine 93

Nitrie reduction at the heme d1 in cytochrome cd1 nitrite reductas (cd1NIR), previously accepted to involve a ferrous-nitro intermediate, is proposed to instead more efficiently involve the nitrito isomer. The nitro mechanism is proposed to be less efficient due to involvement of a less catalytically competent ferric nitric oxide adduct.

Byline: V. M. Ivanov (1), V. N. Figurovskaya (1), N. I. Ershova (2), A. F. Alyukaeva (3), A. G. Tsytsarin (4) Abstract: The Chromotrope 2B reagent was used as an analytical reagent for the direct determination of nitrite ions by sorption chromaticity measurements, diffuse reflectance spectrometry, and solid-phase spectrophotometry. The silochrom C-120 silica gel and the AV-17 anion exchanger were used as supports. Optimum conditions were found for the formation and sorption of Chromotrope 2B. The dependence of the chromaticity characteristics (chromaticity coordinates, lightness, color saturation, yellowness, and whiteness) on the concentration of nitrite ions was examined. The advantages of the use of chromaticity characteristics over the diffuse reflection coefficient were demonstrated. A procedure was developed for the test and sorption--optical determination of nitrite ions in sea water. Author Affiliation: (1) Department of Chemistry, Moscow State University, Vorob'evy gory, Moscow, 119992, Russia (2) Moscow Institute of Radioengineering, Electronics, and Automation, pr. Vernadskogo 78, Moscow, 117454, Russia (3) State Institute of Oceanography, Kropotkinskii per. 6, Moscow, 119034, Russia (4) Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovskii pr. 36, Moscow, 117997, Russia Article History: Registration Date: 06/10/2004

Recently, substantial evidence has emerged that revealed a very close association between the formation of nitrotyrosine and the presence of activated granulocytes containing peroxidases, such as myeloperoxidase. Peroxidases share heme-containing homology and can use [H.sub.2][O.sub.2] to oxidize substrates. Heme is a complex of iron with protoporphyrin IX, and the iron-containing structure of heme has been shown to be an oxidant in several model systems where the prooxidant effects of free iron, heme, and hemoproteins may be attributed to the formation of hypervalent states of the heme iron. In the current study, we have tested the hypothesis that free heme and iron play a crucial role in N[O.sub.2]-Tyr formation. The data from our study indicate that: (i) heme/iron catalyzes nitration of tyrosine residues by using hydrogen peroxide and nitrite, a reaction that revealed the mechanism underlying the protein nitration by peroxidase, [H.sub.2][O.sub.2], and N[O.sup.-.sub.2]; (ii) [H.sub.2][O.sub.2] plays a key role in the protein oxidation that forms the basis for the protein nitration, whereas nitrite is an essential element that facilitates nitration by the heme(Fe), [H.sub.2][O.sub.2], and the N[O.sup.-.sub.2] system; (iii) the formation of a Fe(IV) hypervalent compound may be essential for heme(Fe)-catalyzed nitration, whereas [O.sup.*-.sub.2] (ONO[O.sup.-] formation), [sup.*]OH (Fenton reaction), and compound III are unlikely to contribute to the reaction; and (iv) hemoprotein-rich tissues such as cardiac muscle are vulnerable to protein nitration in pathological conditions characterized by the overproduction of [H.sub.2][O.sub.2] and N[O.sup.-.sub.2], or nitric oxide. nitric oxide | hydrogen peroxide | nitrite | peroxidase

The reaction of ebselen and its derivatives with peroxynitrite anion (PN) is studied in the gas and aqueous phases. It is observed that ebselen reacts with PN to exhibit glutatione peroxidase activity.

The oxidation of nitrite by hypobromite/ hypobromous acid solutions was carried out at different ionic strengths in the presence of different supporting electrolytes and the rate coefficients for oxidation of nitrite by Br (I) was determined in three different ionic strengths in two ionic environments. Under all conditions, nitrite oxidation by HOCL/ ClO(super -) was faster than that by HOBr/BrO(super -).

The production of dihydroxylamine (HNO (sub 2)(super -).) and hydronitrite (NO2 (super 2-.)) radical ions is described. The major revision of the reductive radiation chemistry of nitrite is represented by this production.

The product distribution of peroxynitrite decay as a function of pH, temperature, and concentration are studied. It is observed that below 5 degree Celsius and pH 7, small amounts of decomposition products nitrite and dioxygen are formed, even when the peroxynitrite concentration is high, and at a higher pH, the decomposition increases at the expense of the isomerization, up to nearly 80 percent at pH10.0 at 5 degree Celsius and 90 percent at 45 degree Celsius.

The reactions of t-butyl nitrite (TBN) and t-butyl alcohol (TBA) on clean and O-covered Rh foils are investigated with the help of time-of-flight mass spectrometry temperature-programmed desorption and Auger electron spectroscopy. The t-butoxy decomposes to acetone and butene through a transiet form of the oxtametallacycle involved in TBN.

Byline: Aditi A. Kapasi (1,2), Nora Gibbons (1,2), Joseph Mattana (1,2), Pravin C. Singhal (1,2) Abstract: Background: Intravenous opiate abusers are susceptible to develop heroin and HIV-associated nephropathies however, the role of opiates in the development of these kidney lesions is not clear. Patients with opiate addiction are prone to recurrent infections. Methods: The effect of morphine was studied on the generation of TNF-[alpha] with or without LPS (lipopolysaccharide) by cultured mouse mesangial cells. In addition, the effect of morphine was evaluated on mesangial cell nitrite production. To evaluate the role of opiate receptors, we studied the effect of naloxone and naltrexone on mesangial cell TNF-[alpha] and nitrite production. To determine the role of TNF-[alpha] on mesangial cell nitrite production, we examined the effect of anti-TNF-[alpha] antibody on morphine-induced nitrite production. Assay of TNF-[alpha] and nitrite production was carried by ELISA and Griess method respectively. Results: Morphine alone did not enhance the generation of TNF-[alpha] by mesangial cells, however, an enhanced (P &lt 0.001) TNF-[alpha] production was observed when mesangial cells were first treated with morphine for 18 h and then activated further with LPS. Maximum release of TNF-[alpha] was seen at a concentration of 10.sup.-12 M of morphine. Opiate receptor antagonists (naloxone and naltrexone) inhibited the effect of morphine. Morphine also amplified (P &lt 0.0002) the effect of LPS on mesangial cell nitrite production. Anti-TNF-[alpha] antibody attenuated morphine induced nitrite generation. Conclusion: We conclude that morphine stimulates the generation of TNF-a by LPS-activated mesangial cells. This effect of morphine seems to be opiate receptor mediated and has a downstream effect in the form of mesangial cell nitrite generation. The present in vitro study provides the basis for a hypothesis that morphine may be playing a role in the development of heroin and HIV-associated nephropathies. Author Affiliation: (1) Department of Medicine, Long Island Jewish Medical Center, New Hyde Park, New York, 11040 (2) Long Island Campus for Albert Einstein College of Medicine, Bronx, New York, 10461 Article History: Registration Date: 05/10/2004

Research has been conducted on the denitrifying bacteria genetic heterogeneity. The use of the single-copy genes that code for nitrite reductases as denitrifyng bacteria molecular markers is discussed.

Research has been conducted on the Paracoccus pantotrophus cytochrome cd (sub)1 nitrite reductase. The cooperativity between the redox centers has been investigated.

The effects of calcium nitrite solution, fly ash, silica fume, and their combination on the alkali-silica reaction were studied experimentally according to ASTM C 227 (mortar bar test). To explore the mechanism of such effects, chemically combined water tests and X-ray diffraction examinations were also conducted. The microstructural information provided by these experiments was in agreement with the macroscopic observations. A neural network analysis was then conducted to study the feasibility of the prediction of a theoretical model. To solve the consequent nonlinear coupled equations, some globally convergent skills were adopted. The results showed that a cascade-correlation algorithm could produce reasonable outputs that coincide with the experimental results after proper training.

CASSCF and CASPT2 calculations were undertaken finding that a singlet methylnitrene is an energy minimum and not a transition state.

Research has been conducted on the nirS gene for Paracoccus pantotrophus cytochrome cd (sub)1 nitrite reductase. The determination of the gene transcription start site and the length of nirS promoter transcripts are discussed.

Isolation and characterization of the encoding nitrate/nitrite permease and nitrite reductase from Synechococcus sp. strain PCC 7002 is discussed. Results demonstrate the effect of nitrate/nitrite permease on marine cyanobacteria.

The preparation of the cycloalkyl nitrites from cycloalkyl alcohol and nitric oxide in acetonitrile solution is described. Results indicate that the detection of the same radical species is photolyzed.

The taxonomic investigations of nitrite oxidizers were conducted using immunoblot analyses performed with three monoclonal antibodies (MAbs) that recognized the nitrite oxidoreductase of the genus Nitrobacter. The MAbs were also employed to identify undescribed isolates and enrichment cultures. Fluorescence in situ hybridization and electron microscopic analyses confirmed results derived from the immunoblot analyses demonstrating that Nitrobacter or Nitrospira cells could be enriched from activated sludge via different substrate concentrations.

The article describes NarX ligand response in isolated membranes in Escherichia coli. Nitrate and nitrite protein phosphorylation simulated above the basal level and the membrane kinase activity are examined.

The article discusses Escherichia coli napF and narG gene expression response to different levels of nitrate. The measurements of nitrate and nitrite levels, and results of cell structure experiments are presented.

The photoelectrochemical reduction of nitrite and nitrate on the surface of electrochemically roughened silver electrode was enhanced by the excitation of surface-plasmon resonances on this surface. The photoinduced electroreduction occurred via photoemission of electrons from the metal followed by the capture of these electrons by electron acceptors. One of the products in this reaction was Ammonia.

The crystal structure of the cytochrome C nitrite reductase enzyme from the microorganism Sulfurospirillum deleyianum is reported. A reaction scheme is proposed to transform the nitrite based on structural and spectroscopic data. The haem arrangement is compared with that of other multi-haem cytochromes, and a family of proteins where the orientation of haem groups is conserved, while structure and function are not, has been identified.

The formation of ONOOH/ONOO- in water was investigated by applying pulse radiolysis of nitrite and nitrate solutions. The overall rate constant of the reaction of *OH with *NO2 was found to be (1.0 +/- 0.2) x 10(raised to power 10)/Ms. The reaction produces almost equal amounts of ONOOH and NO3- + H+. The overall constant of the reaction of *NO2 with O*- was found to be (3-4) x 10(raised to power 9)/Ms. The rate constants of ONOO- decomposition at pH 13 and 14 were found to be 1.3 x 10(raised to power -5) and 1.1 x 10(raised to power -5)/s, respectively, and the yield of NO2- was found to be ca. 50%.

This paper describes the application of reverse polarity capillary zone electrophoresis (CZE) for rapid and accurate determination of nitrate and nitrite in natural water samples. Using hexamethonium bromide (HMB) as an electroosmotic flow modifier in a borate buffer at pH 9.2, the resolution of nitrate and nitrite was accomplished in less than 3 min. CZE was compared with ion chromatographic (IC) and cadmium reduction flow injection analysis (Cd-FIA) methods which are the two most commonly used standard methods for the analysis of natural water samples for nitrate and nitrite. When compared with the IC method for the determination of nitrate and nitrite, CZE reduced analysis time, decreased detection limits by a factor of 10, cut laboratory wastes by more than 2 orders of magnitude, and eliminated interferences commonly associated with IC. When compared with the cadmium reduction method, CZE had the advantage of simultaneous determination of nitrate and nitrite, of being able to be used in the presence of various metallic ions that normally interfere in cadmium reduction, and of decreased detection limits by a factor of 10.

The nirA gene encoding the blue nitrite reductase from Alcaligenes xylosoxidans was exported to the periplasm when overexpressed in Escherichia coli. The recombinant enzyme was similar from the enzyme isolated directly from A. xylosoxidans. Electron paramagnetic resonance spectroscopy and metal analyses showed that isolated recombinant Nir possessed only type 1 copper centers and had low nitrite reductase enzyme activity.

Research was conducted to identify the nir operon encoding the dissimilatory NADH-dependent nitrite reductase NirBD; the putative oxidase and chelatase SirA, the uroporphyrinogen III methylase Sir B and NirR. The molecular characterization of the nitrite reductase-negative staphylococcus carnosus Tn917 mutant showed that the sequence characteristics of the nitrite reductase NirB is similar to the NADH-dependent nitrite reductase of Escherichia coli. Results demonstrate that NirR is required for nir promoter activity.

Pattern formation by enteric bacteria growing on semi-solid agar plates have been previously reported. A similar phenomenon was found in an environmental isolate, Pseudomonas strain KC. Five other species of pseudomonads were tested under similar conditions but none formed patterns. Oxygen microelectrode investigations showed that there is little or no oxygen within the aggregates. The growth of strain KC was progressively restricted in imposed diffusion gradients of NO2- or NO3- of which NO2- was the stronger inhibitor.

Current methods for analyzing nitrite levels in rainwater have been less than precise. Either contamination of the specimen or levels of nitrite below the detectable level of the techniques have resulted in questionable data. A new technique, however, has been studied, and has produced interesting results. The study examined rain water acquired from Wilmington, NC for 21 months. The results showed that during El Nino rains and summer tropical rains nitrite levels were less than half that of non-El Nino and tropical rains. This suggests a terrestrial nitrite source.

A study was conducted to analyze the catalysis of the Baylis-Hillman reaction associated with the coupling of an unsaturated carbonyl compound/nitrile with aldehydes. Reactions were carried out utilizing tert-butyl acrylate and benzaldehyde with various Lewis acids. Results indicated that the use of catalytic amounts of oxygen-rich donor ligands supported an increase in reaction rate.

A study was conducted to analyze the loss of ammonia monooxygenase activity in Nitrosomonas europaea after nitrite exposure. The loff oa ammonio monooxygenase activity came under aerobic and anaerobic conditions. Results indicated that the nitrite toxicity in N. europaea is influenced by a novel mechanism specific for ammonia monooxygenase. However, during the presence of substrates of ammonia monooxygenase, the loss was not observed.

A study was conducted to investigate the complexities of peroxynitrite chemistry to understand the formation of hydroxyl radicals during thermal decomposition at room temperature. Stoppe-flow kinetics and product analyses by unequivocal methods were performed. Results identified the rearrangement of nitric acid through the in-cage collapse of the singlet HO./NO2 radical pair as the main decomposition pathway of hydroxyl radicals in water.

A study was conducted to characterize spectroscopic, kinetic and electrochemical analyses of heterologously determined wild-type nitrite reductase from Rhodobacter sphaeroides. A Shimadzu dual beam spectrophotometer was utilized to record optical spectra while potentials were determined with an Ingold-Metler/Toleda combined redox electrode. Results showed that the wild-type enzyme supported a blue-green Type I optical spectrum and a 247-mV Type 1 midpoint potential.

A study was conducted to examine the Type 1 and Type 2 copper ligand environment associated with wild-type and mutant forms of copper-containing nitrite reductase. ENDOR measurements were carried out under dispersion and rapid passage conditions while ENDOR features for Type 2 copper were determined on the low field extremum. Results suggested that nitrite-induced decreased covalency would correlate with an increased Type 2 redox potential to support electron transfer to the Type 2 center.

The dinoflagellate cultures of Scrippsiella trochoidea and Alexandrium minutum were allowed to grow in filter-sterilized sea water with 5 uM nitrate and 0.2 uM phosphate for the purpose of observing their release of nitrite. Macro-nutrients were fed to the cultures to give 10 uM phosphate with either 50 uM nitrate or 25 uM of nitrate and ammonium. A. minutum released a proportion of the nitrate consumed during the dark phase as nitrite when supplied with nitrate and ammonium, indicating a rate-limiting process of nitrite reduction and weak regulation of inorganic-N uptake and assimilation.

Photoinhibition of nitrite reduction caused light-mediated nitrite accumulation of Pseudomonas sp. strain JR12. This was gleaned in an examination of the effect of light on the denitrifying capacity of this nonphotosynthetic denitrifier. Inhibition of nitrite reduction in cells illuminated with green light was the highest, as against inhibition upon exposure to blue and red light. Exposure of the cells to light caused a photooxidation of cytochrome c, affirming that light exposure prevents electron flow from cytochrome c to nitrite reductase.

Halide metathesis with silver nitrite can be used for either stepwise or complete substitution of all three chloride ligands in the iron(III) compound (NEt4)(HB(3,5-Me2pz)3FeCl) to produce the complexes (NEt4)(HB(3,5-Me2pz)3Fe(ONO)xCl3-x), x = 1 - 3, and (NEt4)(HB(3,5-Me2pz)3Fe(eta2-ONO)Cl). The above compounds were characterized by elemental analyses, electrochemistry and spectroscopy. The crystal structures of the ferric complexes had monodentate, O-bound nitrito ligands.

A study was conducted on the reaction chemistry of osmium porphyrins with thionitrites and alkyl nitrites as well as the mode of interaction of RSNO with osmium porphyrins. The findings indicate that the reactions of thionitrites and alkyl nitrites with OsII porphyrins result in nitrosyl thiolates and alkoxides. However, in the case of OsIII, the isolation is limited to the osmium nitrosyl difluorophosphate complex.

Bacillus subtilis has been indentified as an ammonifying bacterium converting nitrate via nitrite into ammonia. Oxygen-sensitive dissimilatory nitrite reductase activity was observed in cell extracts prepared from both strains with benzyl viologen as an electron donor and nitrite as an electron acceptor. The anaerobic expression of the discovered nitrite reductase activity also depends on the regulatory system encoded by resDE.

The preparation and electrochemical characterization of glassy carbon electrodes (GCEs) modified with electropolymerized films of the cation N-(3-pyrrol-1-yl-propyl)-4,4[prime]-bipyridine (PPB) are described. The behavior of a new biosensor, which exhibits a high catalytic activity for nitrite reduction and which consists of a maltose binding protein nitrite reductase fusion (MBP-Nir) immobilized on an electropolymerized film of PPB as an electrocatalyst, is also described. The insoluble perchlorate salt of the poly(benzyl viologen) dication was used to immobilize MBP-Nir onto an electrode previously modified with an electropolymerized film of PPB. The electropolymerized film of PPB on the GCE is redox active and exhibits special electron-transfer properties toward the MBP-Nir layer but not toward Nir (Nir without MBP fusion attached), suggesting an intimate interaction between the PPB film and the MBP-Nir layer. The kinetics of the catalytic reaction between the biosensor and nitrite anion were characterized using cyclic voltammetry and rotated disk electrode techniques, and a value of (4.6 [+ or -] 0.5) x [10.sup.3] [M.sup.-1] [s.sup.-1] was obtained for the rate constant.