Reaction Of Nitrite Research Articles

Red blood cell membrane-facilitated release of nitrite-derived nitric oxide bioactivity.

The reduction of nitrite by deoxyhemoglobin to nitric oxide (NO) has been proposed as a mechanism for the transfer of NO bioactivity from the red blood cell (RBC) to the vasculature. This transfer can increase vascular dilatation. The major challenge to this hypothesis is the very efficient scavenging of NO by hemoglobin, which prevents the release of NO from RBCs. Previous studies indicate that the reaction of nitrite with deoxyhemoglobin produces two metastable intermediates involving nitrite bound to deoxyhemoglobin and a hybrid intermediate [Hb(II)NO(+) ↔ Hb(III)NO] where the nitrite is reduced, but unavailable to react with hemoglobin. We have now shown how unique properties of these intermediates provide a pathway for the release of NO bioactivity from RBCs. The high membrane affinity of these intermediates (>100-fold greater than that of deoxyhemoglobin) places these intermediates on the membrane. Furthermore, membrane-induced conformational changes of the nitrite-reacted intermediates facilitate the release of NO from the hybrid intermediate and nitrite from the nitrite-bound intermediate. Increased membrane affinity, coupled with facilitated dissociation of NO and nitrite from the membrane-bound intermediates, provides the first realistic mechanism for the potential release of NO and nitrite from the RBC and their potential transfer to the vasculature.

Nitrosopersulfide (SSNO-) targets soluble guanylyl cyclase and induces vasodilation in vivo

Background Recent experimental evidence suggests that nitric oxide (NO) and hydrogen sulfide signaling pathways are intimately intertwined particularly in the vasculature, with mutual attenuation or potentiation of biological responses under control of the soluble guanylyl cyclase (sGC) / phopshodiesterase (PDE) pathway. There is now compelling evidence that part of the NO/sulfide cross talk has a chemical foundation via the formation of S/N-hybrid molecules including thionitrous acid (HSNO) and nitrosopersulfde (SSNO-). The aim of this study was to characterize the bioactive products of the interaction between sulfide and NO metabolites targeting sGC that may potentially regulate vasodilation. Results We found that the chemical interaction of sulfide with NO or nitrosothiols leads to formation of S/N-hybrid metabolites including SSNO- via intermediate formation of HSNO. Contrary to a recent report in the literature but consistent with the transient nature of HSNO, its formation was not detectable by high-resolution mass spectrometry under physiologically relevant conditions. SSNO- is also formed in non-aqueous media by the reaction of nitrite with oxidized sulfur species including colloidal sulfur and polysulfides. SSNO- is stable in the presence of high concentrations of thiols, release NO, and activates sGC in RFL-6 cells in an NO-dependent fashion. Moreover, SSNO- is a potent vasodilator in aortic rings in vitro and lowers blood pressure in rats in vivo. The presence of high concentrations of SOD or thiols does not affect SSNO- mediated sGC activation, while it potentiates and inhibits the effects of the nitroxyl (HNO) donor Angeli's salt, suggesting that HNO release from SSNO- is not involved in sGC activation. Conclusion The reaction between NO and sulfide leads to fomation of S/N-hybrid molecules including SSNO-, releasing NO, activating sGC and inducing vasodilation. SSNO- is considerably more stable than HSNO at pH 7.4 and thus a more likely biological mediator that can account for the chemical cross-talk between NO and sulfide.

Introduction of a spectrophotometric method for simultaneous determination of nitrite and nitrate in water samples using partial least squares

A simple and sensitive spectrophotometric method for simultaneous determination of nitrite and nitrate was introduced. The method is based on the reaction of nitrite and nitrate with 2,4-xylenol as reagent in the concentrated sulfuric acid. Calibration curves were linear in the range of 0.2–20.0 and 0.5–7.0 mg L−1 for nitrite and nitrate, respectively. Due to the severe spectral overlapping of the reaction products of two anions with 2,4-xylenol, partial least squares (PLS) was used for simultaneous determination of nitrite and nitrate in the mixtures. For calibration and validation, 25 binary mixtures of nitrite and nitrate (17 calibration and eight external test samples) were designed by simplex lattice design with lattice degree of one. PLS models with Q 2 values of 0.988 and 0.976 were constructed for nitrite and nitrate, respectively. The validated models were used to analyze real water samples. With the recommended method, simultaneous determination of nitrite and nitrate in water samples is possible with satisfactory results.

Wheat fiber colored with a safflower (Carthamus tinctorius L.) red pigment as a natural colorant and antioxidant in cooked sausages

This study was conducted to evaluate the effects of nitrite and wheat fiber (WFC) colored with a safflower (Carthamus tinctorius L.) red pigment on the color characteristics and lipid oxidation of cooked sausages. The safflower red pigment (carthamin) was extracted at alkali condition, and wheat fiber was colored with the extracted safflower red pigment. Total six cooked sausage treatments were prepared with two nitrite levels (0 and 120 ppm) and three WFC levels (0, 1, and 2%). As the WFC level was increased, redness of cooked sausages increased, regardless of presence/absence of nitrite. Carthamin contained in WFC could promote a reaction and/or decomposition of nitrite, resulting in increased nitrosoheme pigment and decreased residual nitrite. In addition, WFC inhibited lipid oxidation of cooked sausages. Consequently, the addition of WFC resulted in positive effects on color formation, residual nitrite, and lipid oxidation, as well as the improvement cooking yield of cooked sausages. Therefore our result suggested that WFC could be possible to partially replace nitrite and coloring of dietary fiber with natural pigments is a useful technique to expand the purposeful use of dietary fiber.

Spectrophotometric determination of nitrite in soil and water using cefixime and central composite design

The present paper seeks to develop a simple method for the spectrophotometric determination of nitrite in soil and water samples and also measure optimum reaction conditions along with other analytical parameters. The method is based on the diazotization-coupling reaction of nitrite with cefixime and 1-naphthylamine in an acidic solution (Griess reaction). The final product that is an azo dye has an orange color with maximum absorption at 360nm which Beer’s Law is obeyed over the concentration range 0.02–15.00mgL−1 of nitrite. Optimal conditions of the variables affecting the reaction were obtained by central composite design (CCD). A detection limit of 4.3×10−3mgL−1 was obtained for determination of nitrite by the proposed method. The proposed method was successfully applied to determine nitrite in soil and water samples. The molar absorptivity of the product of the reaction and RSD in determination of nitrite in real samples are 4.1×103 (Lmol−1cm−1) and lower than 10%, respectively.

Gold nanocluster-enhanced peroxynitrous acid chemiluminescence for high selectivity sensing of nitrite

The weak CL emission of peroxynitrous acid (ONOOH) produced from the reaction of nitrite with hydrogen peroxide in acidic medium was greatly enhanced by Au NCs.

Facile nitrite reduction in a non-heme iron system: formation of an iron(III)-oxo.

Reaction of tetrabutylammonium nitrite with [N(afa(Cy))3Fe(OTf)](OTf) cleanly resulted in the formation of an iron(III)-oxo species, [N(afa(Cy))3Fe(O)](OTf), and NO(g). Formation of NO(g) as a byproduct was confirmed by reaction of the iron(II) starting material with half an equivalent of nitrite, resulting in a mixture of two products, the iron-oxo and an iron-NO species, [N(afa(Cy))3Fe(NO)](OTf)2. Formation of the latter was confirmed through independent synthesis. The results of this study provide insight into the role of hydrogen bonding in the mechanism of nitrite reduction and the binding mode of nitrite in biological heme systems.

Sulfation of Hydroxyethyl Cellulose by N(SO3Na)3 and the Anticoagulant Activity of Sulfated Hydroxyethyl Cellulose

Hydroxyethyl cellulose sulfate (HECS) was synthesized by sulfation of hydroxyethyl cellulose with N(SO3Na)3, which was manufactured by reaction of sodium bisulfite and sodium nitrite. Barium sulfate nephelometry and light scattering method were used to determine degrees of substitution (DSs) and molecular weights (Mws), respectively. Sulfate products with DS values from 0.26 to 1.88 and Mw in the range of 12.1–54.8 kDa were obtained at temperatures from 30°C to 80°C. Furthermore, the anticoagulant activity of HECS with different DSs, concentrations, and Mws was studied. Clotting assays revealed that the introduction of sulfate groups into hydroxyethyl cellulose could improve its anticoagulant activity.

Computational Study of Energy Disposition in Domino Reaction

Abstract The domino reaction of (10-oxotricyclo[4.2.1.12,5]deca-3,7-dien-9-yl)methyl nitrite (1) with the hydroxide ion was analyzed by DFT calculations and molecular dynamics simulations to study the effect of kinetic energy produced as the reaction proceeds on the reaction mechanism. Energy disposition in the reactive intermediates was observed. The kinetic energy was found to act as a driving force for the second step of the domino reaction.

Development and Optimization of a SERS Method for On-site Determination of Nitrite in Foods and Water

A rapid, sensitive, and selective detection method of nitrite in foods and water was established by surface-enhanced Raman spectroscopy (SERS) based on the diazo reaction of nitrite with p-nitroaniline and 1-naphthylamine in acidic solution. The azo dye (4-(4-nitrophenyldiazenyl)naphthalene-1-aminium, NNA), which was derived from the diazo reaction, was determined by SERS using citrate-coated silver nanoparticles (AgNPs) as SERS substrates. The concentrations of nitrite in samples were finally calculated from the intensities of SERS signals generated by NNA in the testing solutions. By using the present method combined with a portable miniature Raman spectrometer, on-site determination of nitrite could be performed easily and efficiently. The effects of several experimental parameters on the intensity of SERS signals, such as the volume of AgNP solution and the mixing time of AgNPs and NNA, were investigated. The linear range of the method was 0.1–10.0 mg L−1. The limits of detection (LODs) were 0.01, 0.03, and 0.05 mg L−1 at 720, 1,459, and 1,609 cm−1, respectively. The method was applied to the determination of nitrite in real food and water samples, with recoveries in the range of 86.9–103.4 % and relative standard deviations (RSDs) less than 9.64 %.

Aqueous two-phase extraction and spectrofluorimetric determination of nitrite with o-phenylenediamine enhanced by hydroxypropyl-β-cyclodextrin in urine samples

An aqueous two-phase extraction process composed of tetrahydrofuran/ammonium sulfate to extract nitrite from urine samples is investigated. The method is based on the reaction of nitrite with o-phenylenediamine in acid media to form benzotriazole and the aqueous two-phase extraction of benzotriazole in the presence of salt as an inducing agent in phase separation, followed by spectrofluorimetric detection. The system of fluorescence intensity was enhanced by complexation of hydroxypropyl-β-cyclodextrin. The optimal reaction and extraction conditions were studied. The linear calibration range for nitrite was 5–1000 ng mL−1 with a detection limit of 1.5 ng mL−1 (S/N = 3). The relative standard deviations for six replicate measurements varied between 0.3% and 1.7%. The interference effects of some anions and cations were also tested. The proposed method was successfully applied for the determination of nitrite in the urine samples with recoveries of 93.3% to 105.0%.

Simple design flow injection PMMA acrylic sample cell for nitrite determination

A polymethyl-methacrylate (PMMA) acrylic sample cell using flow injection is developed in this research for the determination of nitrite in an aqueous media. The research focuses on exhibiting direct absorbance spectrophotometry of nitrite using concentration of samples ranging from 0.1078 to 1.725 ppm. Nitrite determination is done colorimetrically using the Greiss reagent method. This method is based on the reaction of nitrite with sulphanilamide acid and N-1-napthylamine (NED) utilizing diazo coupling, and a syringe is used to administer the nitrite solution. The sample cell being used possesses a diameter of 1 mm with an overall size of 7.35×22 mm2. To gauge the direct absorbance, a wavelength range from 400 to 650 nm has been selected for the testing, and the maximum absorbance is found to be at 545 nm. The validity of the proposed cell is explained in this letter.

Upconversion nanoparticles for ratiometric fluorescence detection of nitrite.

We have developed a selective upconversion switching method for the ratiometric fluorescence detection of nitrite using upconversion nanoparticles (UCNPs) and an efficient nitrite reaction. The green emission (λ(em) = 539 nm) of NaYF4:Yb(3+),Er(3+) nanoparticles can be selectively quenched by the neutral red (NR) dye due to the spectral overlap between the emission at 539 nm and the absorption of NR, while its red emission (λ(em) = 654 nm) remains unchanged. Nitrite reacts specifically and strongly with NR to form diazonium salt and lose the diazonium group, which sharply decreases the absorption of NR. Thus, the green emission of NaYF4:Yb(3+),Er(3+) can be recovered by increasing the amount of nitrite, leading to visible color changes from red to orange-yellow and finally green under excitation at 980 nm. The increase in the ratio of emission intensities (I539/I654) is quantitatively correlated to the concentration of nitrite ions. Moreover, the developed method has been successfully applied to nitrite detection in real samples such as drinking water, natural water and meat foods. In particular, the upconversion sensors can efficiently avoid background optical interference and thus show potential for the detection of nitrite salts in complex samples.

ChemInform Abstract: Methylsulfonic Acid Adsorbed on Silica Gel as a Solid Acid for Dimerization of Indoles: A Convenient Synthesis of 2,3′‐Bi(3H‐indol)‐3‐one Oximes.

Abstract A simple, convenient, and efficient approach for the synthesis of (E)-2,3′-bi(3H-indol)-3-one oxime derivatives has been developed. The methodology is based on a three-component coupling reaction of indoles and sodium nitrite using a silica-supported methylsulfonic acid as solid acid. The practical utility of this three-component coupling reaction has been demonstrated in the gram-scale dimerization of indole. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]

Study the biocatalyzing effect and mechanism of cellulose acetate immobilized redox mediators technology (CE-RM) on nitrite denitrification

The biocatalyzing effect of a novel cellulose acetate immobilized redox mediators technology (CE-RM) on nitrite denitrification process was studied with anthraquinone, 1,8-dichloroanthraquinone, 1,5-dichloroanthraquinone and 1,4,5,8-tetrachloroanthraquinone. The results showed that the immobilized 1,4,5,8-tetrachloroanthraquinone presented the best biocatalyzed effect which increased nitrite denitrification rate to 2.3-fold with 12 mmol/L 1,4,5,8-tetrachloroanthraquinone. The unequal biocatalyzing effect was due to the quantity and position of -Cl substituent in anthraquinone-structure. Moreover, the nitrite denitrification rate was increased with the oxidation reduction potential (ORP) values becoming more negative during the biocatalyzing process. The stabilized ORP value with 12 mmol/L immobilized 1,4,5,8-tetrachloroanthraquinone were 81 mV lower than the control. At the same time, the more OH(-) was produced with the higher nitrite removal rate achieved in the nitrite denitrification process. In addition, a positive linear correlation was found between the nitrite removal reaction constants k [gNO2(-)-N/(gVSS d)] and immobilized 1,4,5,8-tetrachloroanthraquinone concentration (C1,4,5,8-tetrachloroanthraquinone), which was k = 1.8443 C1,4,5,8-tetrachloroanthraquinone + 33.75(R(2) = 0.9411). The initial nitrite concentration of 179 mgNO2(-)-N/L resulted in the maximum nitrite removal rate, which was 6.526[gNO2(-)-N/(gVSS d)]. These results show that the application of cellulose acetate immobilized redox mediators (CE-RM) can be valuable for increasing nitrite denitrification rate.

Simplified Nitrate-Reductase-Based Nitrate Detection by a Hybrid Thin-Layer Controlled Potential Coulometry/Spectroscopy Technique

A novel method for the detection of nitrate was developed using simplified nitrate reductase (SNaR) that was produced by genetic recombination techniques. The SNaR consists of the fragments of the Mo-molybdopterin (MO-MPT) binding site and nitrate reduction active site and has high activity for nitrate reduction. The method is based on a unique combination of the enzyme-catalyzed reduction of nitrate to nitrite by thin-layer coulometry followed by spectroscopic measurement of the colored product generated from the reaction of nitrite with Griess reagents. Coulometric reduction of nitrate to nitrite used methyl viologen (MV(2+)) as the electron transfer mediator for SNaR and controlled potential coulometry in an indium tin oxide (ITO) thin-layer electrochemical cell. Absorbance at 540 nm was proportional to the concentration of nitrate in the sample with a linear range of 1-160 μM and a sensitivity of 8000 AU M(-1). The method required less than 60 μL of sample. Detection of nitrate could also be performed by measuring the charge associated with coulometry. However, the spectroscopic procedure gave superior performance because of interference from the large background charge associated with coulometry. Results for the determination of nitrate concentration in several natural water samples using this device with spectroscopic detection are in good agreement with analysis done with a standard method.

Reduction of nitrite and nitrate on nano-dimensioned FeS.

The reaction of nitrite (NO2(-)) and nitrate (NO3(-)) on nanometer-sized FeS particles was investigated in alkaline (initial pH = 10.3) solutions at reaction temperatures of 22, 70, and 120 °C using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and fluorescence spectroscopy that allowed an analysis of adsorbate complexation on the FeS and reaction product in the aqueous phase, respectively. ATR-FTIR showed that NO was a surface-bound intermediate on FeS during its exposure to NO2(-) at all three reaction temperatures. Ammonia/ammonium (NH3/NH4(+)) product was also produced when FeS was exposed to NO2(-) at the 70 °C and 120 °C reaction temperatures. Activation of NO3(-) to form surface-bound NO was experimentally observed to occur at 120 °C on FeS, but not at the lower reaction temperatures. Furthermore, NH3/NH4(+) product in the aqueous phase was only present during the reaction of FeS with NO3(-) at the highest temperature used in this study.

Methylsulfonic Acid Adsorbed on Silica Gel as a Solid Acid for Dimerization of Indoles: A Convenient Synthesis of 2,3′-Bi(3H-indol)-3-one Oximes

A simple, convenient, and efficient approach for the synthesis of (E)-2,3′-bi(3H-indol)-3-one oxime derivatives has been developed. The methodology is based on a three-component coupling reaction of indoles and sodium nitrite using a silica-supported methylsulfonic acid as solid acid. The practical utility of this three-component coupling reaction has been demonstrated in the gram-scale dimerization of indole. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource: Full experimental and spectral details.]

A model for the nitric oxide producing nitrite reductase activity of hemoglobin as a function of oxygen saturation

The production of nitric oxide by the nitrite reductase activity of hemoglobin has been proposed to play a major role in hypoxic vasodilation. The bimolecular reaction rate constant for nitric oxide formation is a complex function of hemoglobin oxygenation stemming from the intrinsic allosteric character of hemoglobin, resulting in an unsymmetrical inverted U shape profile of activity versus oxygen saturation. We present an analysis of the hemoglobin nitrite reductase activity based on the Monod Wyman Changeux (MWC) allosteric model and derive a set of equations that enabled us to express the rate constant of bimolecular reaction of nitrite with hemoglobin as a function of hemoglobin saturation and use this expression to explore the factors controlling the shape of the nitrite reductase activity versus hemoglobin saturation curve. From the value of the maximum reductase activity, we derive equations to calculate microscopic nitrite reductase reaction rate constants for the R and T quaternary states. We have also developed two methods to parameterize the MWC model based on the Hill equation, with its parameters, h and P50, and the knowledge that these two descriptions of the binding curve coincide in the region of the curve where h is defined. This has allowed the calculation of the hemoglobin nitrite reductase activity rate profiles for the human hemoglobin and for bovine hemoglobin. The properties of these rate profiles are discussed.

History and Physical Examination Plus Laboratory Testing for the Diagnosis of Adult Female Urinary Tract Infection

Emergency physicians often encounter females presenting with symptoms suggestive of urinary tract infections (UTIs). The diagnostic accuracy of history, physical examination, and bedside laboratory tests for female UTIs in emergency departments (EDs) have not been quantitatively described. This was a systematic review to determine the utility of history and physical examination (H&P) and urinalysis in diagnosing uncomplicated female UTI in the ED. The medical literature was searched from January 1965 through October 2012 in PUBMED and EMBASE using the following criteria: Patients were females greater than 18 years of age in the ED suspected of having UTIs. Interventions were H&P and urinalysis used to diagnose a UTI. The comparator was UTI confirmed by a positive urine culture. The outcome was operating characteristics of the interventions in diagnosing a UTI. Study quality was assessed using Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2). Sensitivity, specificity, and likelihood ratios (LRs) were calculated using Meta-DiSc. Four studies (pooled n = 948) were included with UTI prevalence ranging from 40% to 60%. H&P variables all had positive LRs (+LR, range = 0.8 to 2.2) and negative LRs (-LR, range = 0.7 to 1.0) that are insufficient to significantly alter pretest probability of UTI. Only a positive nitrite reaction (+LR = 7.5 to 24.5) was useful to rule in a UTI. To rule out UTI, only a negative leukocyte esterase (LE; -LR = 0.2) or blood reaction on urine dipstick (-LR = 0.2) were significantly accurate. Increasing pyuria directly correlated with +LR, and moderate pyuria (urine white blood cells [uWBC] > 50 colony-forming units [CFUs]/ml) and moderate bacteruria were good predictors of UTI (+LR = 6.4 and 15.0, respectively). No single H&P finding can accurately rule in or rule out UTI in symptomatic women. Urinalysis with a positive nitrite or moderate pyuria and/or bacteruria are accurate predictors of a UTI. If the pretest probability of UTI is sufficiently low, a negative urinalysis can accurately rule out the diagnosis.