Reduction of nitrates,the no donors,by hemoglobin in the presence of cysteine

Hemoglobin (Hb) reduces 3,3-bis(nitroxymethyl)oxetane (NMO) only in the presence of cysteine (Cys) via intermediate cysteine thionitrate. The kinetics of the reaction of NMO with Cys and the kinetics and mechanism of formation of NO in the ternary system Hb-NMO-Cys were studied. The formation rate of Hb-NO in the ternary system is higher than that of Hb-NO in the reaction of Hb only with NO ₂ ⁻ generated in the binary system NMO-Cys. The second-order rate constants of the main reaction steps in the system Hb-NMO-Cys were estimated by simulating the kinetics of the reactions with a system of equations taking into account equilibria between all components of the reaction mixture. Hemoglobin reduces cysteine thionitrate, the intermediate in the reaction of NMO with Cys, to NO. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–731, April, 2007.     

Synthesis and structures of 3-hydroxy-6-(R-phenylazo)-7,8-benzo-1,2,3,4-tetrahydroquinolines as products of analytical test reactions for nitrite and nitrate anions

An improved procedure was proposed for the synthesis of 3-hydroxy-7,8-benzo-1,2,3,4-tetrahydroquinoline, which is used as a reagent for the analytical test reaction for nitrate and nitrite anions based on azo coupling with diazo compounds. 3-Hydroxy-6-(R-phenylazo)-7,8-benzo-1,2,3,4-tetrahydroquinolines (R = 2-COOH, 4-COOH, or 4-SO₃H) were synthesized by azo coupling reactions in 65–70% yields. The structures of these compounds were confirmed by elemental analysis, ¹H NMR and IR spectroscopy, and X-ray diffraction. Based on the X-ray data, the bathochromic shift in the UV spectrum of the o-carboxy isomer compared to the p-carboxy isomer (Δλ_max = 50 nm) is attributed to a strong intramolecular hydrogen bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1027–1031, June, 2006     

2-R-6-ethyl-7-hydroxy-3-(5-phenyl-1,3,4-thiadiazolyl-2)chromones

-(5-Phenyl-1,3,4-thiadiazolyl-2)-6-ethyl-2,4-dihydroxyacetophenone was synthesized by the condensation of 4-ethylresorcinol with 2-cyanomethyl-5-phenyl-1,3,4-thiadiazole. Interaction of the former with carboxylic acid anhydrides and halides and subsequent hydrolysis gave 2-R-6-ethyl-7-hydroxy-3-(5-phenyl-1,3,4-thiadiazoyl)chromones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, 1840–1847, December, 2004.     

2-二乙氨基-4-羟基-6-甲基嘧啶的合成

二乙基胍硝酸盐;硝酸盐;BTEA;2-二乙氨基-4-羟基-6-甲基嘧啶的合成     

TEA法测定NO2的反应机理研究

应用FABMS、NMR、IR、HPLC和紫外吸收光谱研究了室温下三乙醇胺与较高浓度NO₂(2.48%)的反应情况,证明反应产物为三乙醇胺硝酸盐和三乙醇胺亚硝酸盐,提出了可能的反应机理,为TEA法监测空气中NO₂的浓度提供了依据.     

Determination of No2 -/NO3 - Mixtures by Titration with Ascorbic Acid

Abstract

The analysis of nitrite-nitrate mixtures by indirect titration with ascorbic acid performed before and after passage through a reducing Cd column is proposed and discussed with particular reference to experimental conditions, calculation scheme and concentration ranges.     

膜渗透与离子色谱联用技术测定蔬菜中亚硝酸盐和硝酸盐

建立了膜渗析与离子色谱联用技术分析蔬菜等复杂基体中亚硝酸盐和硝酸盐的方法。蔬菜样品经沸水浴后,试样液通过膜渗析除去水溶性大分子杂质和颗粒,直接进入离子色谱分析。渗析池采用0.20μm的醋酸纤维为渗析膜,以水为接收液,分析柱为Metrosep A Supp4-250阴离子交换柱,以1.8mmol/L Na2CO3 1.7mmol/L NaHCO3为流动相,采用化学抑制电导检测。以20g称样计量,方法中NO2-、NO3-的检出限分别为0.075mg/kg和0.105mg/kg;实际样品的加标回收率分别为80.6%~98.7%和90.5%~114%;相对标准偏差(RSD)≤10%。本方法前处理简单,重现性好,准确度高。     

6-烷氧基-7-乙基-4-羟基-3-喹啉羧酸乙酯的合成及抗球虫活性研究

本文设计并合成了2个新的6-烷氧基-7-乙基-4-羟基-3-喹啉羧酸乙酯化合物.所有化合物的结构均经HRMS,1H NMR,IR和元素分析所证实.对2个化合物进行了抗球虫活性实验,结果表明,化合物6-正十四烷氧基-7-乙基-4-羟基-3-喹啉羧酸乙酯具有抗球虫效果,并有可能作为抗球虫药物使用.目标物制备方法具有合成路线短、产率高、原料易得和总生产成本低的优点.     

比光谱-导数-紫外分光光度法同时测定水中硝酸根和亚硝酸根

利用二元混合物的混合光谱与其中某一组分光谱的比值对波长求导，可达到分辨重叠光谱的目的。本文研究了用比光谱-导数-紫外分光光度法同时测定水样中NO3-和NO2-，以“减法技术”求导，兼具导数光度法能消除低频背景和高频噪声干扰及线性回归法分辨能力强的优点。方法避免了一般光度法需加入试剂而可能引起的误差。在pH7～9条件下测量203um～219um的光吸收值，用比光谱-导数技术处理，同时测定合成试样中0～4mg／L的NO3-和NO2-，6次测定相对标准偏差＜7％，加入回收率在95％～101％之间。讨论了干扰离子的影响及消除，并与P-矩阵法作了比较。方法已用于井水、雨水及湖水中NO3-和NO2-的同时测定。     

N－芳基－2－乙基－3－羟基－4－吡啶酮的微波合成

用微波辐射从2－乙基－3－羟基－4－吡喃酮和芳胺合成了系列N－芳基－2－ 乙基－3－羟基－4－吡啶酮，并对产物进行了紫外、红外、氢核磁和质谱表征。     

Transport of hydrated nitrate and nitrite ions through graphene nanopores in aqueous medium

Nitrate () and nitrite () ions are naturally occurring inorganic ions that are part of the nitrogen cycle. High doses of these ions in drinking water impose a potential risk to public health. In this work, molecular dynamics simulations are carried out to study the passage of nitrate and nitrite ions from water through graphene nanosheets (GNS) with hydrogen-functionalized narrow pores in presence of an external electric field. The passage of ions through the pores is investigated through calculations of ion flux, and the results are analyzed through calculations of various structural and thermodynamic properties such as the density of ions and water, ion–water radial distribution functions, two-dimensional density distribution functions, and the potentials of mean force of the ions. Current simulations show that the nitrite ions can pass more in numbers than the nitrate ions in a given time through GNS hydrogen-functionalized pore of different geometry. It is found that the nitrite ions can permeate faster than the nitrate ions despite the former having higher hydration energy in the bulk. This can be explained in terms of the competition between the number density of the ions along the pore axis and the free energy barrier calculated from the potential of mean force. Also, an externally applied electric field is found to be important for faster permeation of the nitrite over the nitrate ions. The current study suggests that graphene nanosheets with carefully created pores can be effective in achieving selective passage of ions from aqueous solutions.     

强碱阴离子交换树脂及碱性洗脱剂的离子排阻/阴离子交换色谱法同时测定NH4+ ，NO2-和NO3-（英文）

Ion-exclusion/anion-exchange chromatography(IEC/AEC) on a combination of a strongly basic anion-exchange resin in the OH——form with basic eluent has been developed.The separation mechanism is based on the ion-exclusion/penetration effect for cations and the anion-exchange effect for anions to anion-exchange resin phase.This system is useful for simultaneous separation and determination of ammonium ion(NH+4),nitrite ion(NO-2),and nitrate ion(NO-3) in water samples.The resolution of analyte ions can be manipulated by changing the concentration of base in eluent on a polystyrene-divinylbenzene based strongly basic anion-exchange resin column.In this study,several separation columns,which consisted of different particle sizes,different functional groups and different anion-exchange capacities,were compared.As the results,the separation column with the smaller anion-exchange capacity(TSKgel Super IC-Anion) showed well-resolved separation of cations and anions.In the optimization of the basic eluent,lithium hydroxide(LiOH) was used as the eluent and the optimal concentration was concluded to be 2 mmol/L,considering the resolution of analyte ions and the whole retention times.In the optimal conditions,the relative standard deviations of the peak areas and the retention times of NH+4,NO-2,and NO-3 ranged 1.28%-3.57% and 0.54%-1.55%,respectively.The limits of detection at signal-to-noise of 3 were 4.10 μmol/L for NH+4,1.87 μmol/L for NO-2 and 2.83 μmol/L for NO-3.     

On the stability of NF4NO3 and a new synthesis of fluorine nitrate

The reaction of NF₄⁺SbF₆⁻ with alkali metal nitrates in either CH₃CN or SO₂ solution at low temperatures produces FONO₂ in quantitative yield. Attempts were unsuccessful to prepare FONO from NF₄SbF₆ and KNO₂ in an analogous manner.     

3-羟基-2-吡啶亚胺异构反应的机理

在RHF-6-31G,MP2/6-31G和MP2/6-31G水平上,对3-羟基-2-吡啶亚胺的气相、水分子作为催化剂的异构化反应进行了研究,结果表明,气象异构难于进行,水分子作为催化剂参与反应过程是目标反应所循的反应路径。     

Determination of Nitrate and Nitrite by Ion-Selective Electrodes in Relation to Gypsum Formation on Some Travertine Buildings in Polluted Atmosphere of Ankara

Abstract

Gypsum formation on calcareous building stones in the polluted atmosphere of cities is thought to be accelerated by the presence of nitrogen-containing compounds. A reliable method for nitrate and nitrite determinations is proposed and the presence of nitrogen compounds is discussed in relation to their possible influence on gypsum formation. Investigations on nitrate and nitrite determinations with ionselective electrodes have been carried out along with gypsum determinations on the samples taken from altered surfaces of some travertine buildings in Ankara. Interfering effects of the ions which may be present in the matrix studied have been examined and the proper masking solutions for their removal have been introduced. Investigations show that nitrate and nitrite determinations with ion-selective electrodes are reliable, rapid and inexpensive in stone extracts. The sulphate to nitrate ratios in this study vary between 32 and 393. These data are compared with earlier results and the possible effects of nitrogen-containing compounds in gypsum formation are discussed.     

脱脂乳粉中硝酸盐、亚硝酸盐标准物质制备技术研究与评估

对脱脂乳粉中硝酸盐、亚硝酸盐标准物质样品制备技术进行了研究与评估。采用基体添加-真空冷冻干燥法制备标准物质候选物。选择乙酸沉淀蛋白-固相萃取/离子色谱紫外检测法对所制备样品进行评估。与国家标准中推荐的离子色谱电导检测器相比,采用紫外检测器可有效避免乳粉基质中存在的共洗脱组分对亚硝酸盐测定的干扰,且测量精密度得到改善,更有利于满足样品制备回收率、均匀性与稳定性评估的技术要求。经考察,样品中亚硝酸盐、硝酸盐目标制备值与测得值吻合,制备回收率分别为91%,101%;经方差分析,最小取样量1.0 g时,由样品中亚硝酸盐与硝酸盐均匀性引入的相对不确定度分别为2.9%和0.3%;-70,-20,4,20,35,45℃下同步、加速稳定性实验与线性回归趋势分析结果表明,样品短期稳定性及-20℃干燥、真空、避光保存条件下的长期稳定性预期良好。本研究确立了乳粉中亚硝酸盐与硝酸盐标准物质研究的可行性,所建立的制备技术可以确保标准物质定值结果的准确性。     

Ab initio investigation on the ion‐associated species and process in Mg(NO3)2 solution

In the present article, two focal subjects, i.e., hydration of the NO and associated ion species in the Mg(NO₃)₂ solution are researched by using the ab initio method. Nitrate ions with the hydration number of 1–6 are optimized at the HF/6‐31+G* level. Their relative energies, binding energies, and v₁‐NO frequencies are also presented. The investigation of the binding energies shows the hydration number is 3–6 in the solvent abundant environment. The associated species, including ion pairings, triple‐ and multiple‐ion clusters, are also optimized at the same level and their v₁‐NO frequencies are calculated for comparing with the results in experiments. From the comparison, the new associated process via aqueous free ions → solvent‐shared ion pairings → solvent‐shared triple and multiple ion clusters → contact multiple ion clusters → amorphous crystal is proposed. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Solubilities of iron(III) complexes of 3-hydroxy-2-ethyl-4-pyranone and of 3-hydroxy-1,2-dimethyl-4-pyridinone in aqueous salt solutions

Solubilities are reported for the tris-ligand–iron(III) complexes of 3-hydroxy-2-ethyl-4-pyranone and of 3-hydroxy-1,2-dimethyl-4-pyridinone in aqueous solutions of alkali halides and of ammonium and tetraalkylammonium bromides. The Setchenow coefficients estimated from salt effects on solubilities for these complexes are compared with those for other inorganic complexes.     

New systems for classical nitrosohalogenation of alkenes 2. Generation of nitrosyl chloride in AgNO<Subscript>2</Subscript>-SOCl<Subscript>2</Subscript> and AgNO<Subscript>3</Subscript>-SOCl<Subscript>2</Subscript> systems

Study of the reactions of compounds of the norbornene series demonstrated that the AgNO₂-SOCl₂ and AgNO₃-SOCl₂ systems serve as nitrosochlorinating agents under the conditions of electrophilic addition. X-ray diffraction study showed that dimerization of cis-exo-2-chloro-3-nitrosobicyclo[2.2.1]heptane occurs heterostereospecifically. The origin of the active principle of the reagents is discussed. For Part 1, see Ref. 1. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2081–2085, September, 2005.     

Fluorometric determination of fluoride ion by reagent tablets containing 3-hydroxy-2'-sulfoflavone and zirconium(IV) ethylenediamine tetraacetate

A reagent tablet for determination of fluoride ion has been prepared using ethylenediamine-N,N,N′,N′-tetraacetate complex of zirconium (Zr-EDTA), 3-hydroxy-2′-flavone (FS) and an appropriate pH buffer. Dissolving of the tablet into water exhibits an intense blue fluorescence (λ_max = 460 nm) upon excitation at 377 nm and the fluorescence intensity decreases with the presence of fluoride ion. Hence, a simple fluorescent detection procedure for fluoride ion in aqueous media was successfully constructed with this tablet. The principle of this detection system is the ligand exchange reaction of FS bound to Zr-EDTA with fluoride ion. The present system provides an easy, rapid and selective determination method of fluoride ion ranging from 5 × 10⁻⁶ to 1 × 10⁻³ mol dm⁻³. The measurement of real samples with this tablet showed the similar results as those by the common method with the Alfusone reagent.