Confirmation of N-(Nitrosomethyl) urea as a Nitrosourea Derived by Nitrosation of Fish Sauce

N-(nitrosomethyl ) urea (NMU ) was characterized in the carcinogenic nitrosated fish sauce (NFS) with high performance liquid chromatography (HPLC )- pholohydrolysis-pyrolysis-thermal en -ergy analysis recently. We used HPLC-electronic spray ionization-mass spectrometry and HPLC-diode array detection to confirm NMU in NFS furiher. It was observed that the corresponding chro-matographic fraction of NMU of NFS showed the same mass spectrum (m/z 64, 102, and 145) andultraviolet-absorbance (λ max = 230 nm) as those of authentic NMU. These results confirmed that thecomponent of NFS was NMU

Nitrosation and Nitration of Tetraacetyldibenzylhexaazaisowurtzitane

Tetraacetyldibenzylhexaazaisowurtzitane (TADBIW) was subjected to debenzylation by nitrosating with inorganic materials available commercially to synthesize tetraacetyldinitrosohexaazaisowurtzitane (TADNSIW). TADNSIW was purified, and its structure was determined by FTIR, 1H NMR, MS and element analysis. The debenzylation reaction of TADBIW gave quantitative benzaldehyde as a by-product. This indicates that the reaction produces an imine cation as an intermediate. Hexanitrohexaazaisowurtzitane (HNIW) was prepared from unpurified TADNSIW with the yield over 96.0 % and the purity more than 98.0 %. And the mechanism of the reaction from TADNSIW to HNIW is proposed to be oxidation of nitroso and nitration of acetyl on the molecule of TADNSIW. This reaction system involved is simple, and the reaction can complete within a short time and under mild conditions. The product can be easily to separate and the waste disposed readily.

Chemoselective N-nitrosation of secondary amines under heterogeneous and mild conditions via in situ generation of HNO_2

A wide variety of secondary amines are chemoselectively subjected to N-nitrosation reaction with treatment of citric acid and NaNO2 in the presence of wet SiO2 （50%, w/w） in dichloromethane at room temperatture under heterogeneous conditions. The Nnitrosation method is very simple and products can be easily isolated with good to high yields.

Comparison of Mechanisms of N-Nitrosation and N-Nitration of Ammonia and Dimethylamine by Reactive Nitrogen Oxygen Species:A Theoretical Study

Reactive nitrogen oxygen species（RNOS） implicate damage in biological systems,especially leading to inflammation,neurodegenerative and cardiovascular diseases,and cancer by altering the functions of biomolecules through the N-nitrosation and N-nitration reactions.The mechanisms of N-nitrosation and N-nitration reactions of ammonia and dimethylamine by RNOS,i.e.,N2O3,N2O4,N2O5 and ONOOH,were investigated at the CBS-QB3 level of theory.The computational results indicate that the N-nitrosation reaction prefers a concerted mechanism,in which a H-abstraction and ON-addition occur simultaneously,whereas a stepwise mechanism（also called a free radical mechanism） is more favorable for most nitrating agents in the N-nitration reaction,where NO2 first abstracts a hydrogen atom from the nitrogen of amines and then the induced intermediate reacts with NO2 once more to form the nitration products.However,the concerted pathway is still a feasible process for some nitrating agents such as N2O5.In addition,the relationship between the structures of different RNOS and their nitrosating or nitrating abilities was also investigated.

Celecoxib enhances the detoxification of diethylnitrosamine in rat liver cancer

AIM： To study the effect of celecoxib （CXB） on diethylnitrosamine activation through the regulation of cytochrome P450 in a hepatocarcinogenesis model.METHODS： Six-week-old male Sprague-Dawley rats were randomly divided into five groups, a non-treated group （NT）, a diethylnitrosamine-treated group （DEN）, a DEN＋CXB-treated group （DEN＋CXB）,and CXB 8 d-treated and CXB 32 d-treated groups. The effects of celecoxib on the enzymatic activities of CYP1A1, 2A, 2B1/2, and 2E1 were assessed in hepatic microsomes 24 h after DEN administration.Changes in CYPIA1 and CYP2B1/2 protein expression were also evaluated. The rate of DEN metabolism was measured by the production of the deethylation metabolite acetaldehyde, and the denitrosation metabolite nitrite.RESULTS： DEN＋CXB administration produced a significant increase in the enzymatic activities ofCYP2B1/2 and 1A1, whereas it did not change the activities of CYP2A and 2E1, compared to that of the DEN group. CXB treatment for eight days did not produce a significant effect on enzymatic activity when compared to the NT group; however, when it was administered for prolonged times （CXB 32 d group）,the enzymatic activities were increased in a similar pattern to those in the DEN＋CXB group. The observed increase in the enzymatic activities in the DEN＋CXB group was accompanied by an increase in the CYP2B1/2 protein levels; no changes were observed in the levels of CYPIA1. In vitro, CXB increased the denitrosation of DEN, a pathway of metabolic detoxification. The addition of SKF-525A, a preferential inhibitor of CYP2B, abrogated the denitrosation of DEN.CONCLUSION： These results suggest that the mechanism of action of CXB involves enhancement of the detoxification of DEN by an increasing denitrosation via CYP2B1/2.

Attenuation of experimentally induced diabetic neuropathy in association with reduced oxidative-nitrosative stress by chronic administration of <i>Momordica charantia</i>

Momordica Charantia (MC) is one of the most famous traditional plant worldwide, used for the treatment of diabetes and its complications. In the present study possible protective effect of MC in Streptozotocin (STZ) induced diabetic neuropathy in mice was evaluated. STZ induced diabetic mice were orally administered MC at various doses (200 - 800 mg/kg) for six weeks. Diabetes induced neuropathic pain was assessed by hot plate test, formalin test and tail flick test at the beginning and end of the study. Serum TBARS, NO and SOD levels were estimated at the end of the study as the markers of oxidative-nitrosative stress. Rotarod test was employed to assess the effect of treatment on motor coordination. The results showed that STZ induced diabetes significantly decreased the pain threshold as was indicated by increased flinching in formalin test and decreased withdrawal latency in hot plate and tail flick tests. Oxidative-nitrosative stress was significantly increased in diabetic animals. Chronic administration of MC significantly attenuated diabetes induced increase in flinches and decrease in withdrawal latency without impacting sensory and motor functions. MC administration also exhibited dose dependant reduction of hyperglycemia and serum TBARS, NO and SOD levels in diabetic mice. The results suggest that long term use of MC protects against diabetes induced neuropathy in association with attenuation of hyperglycemia and oxidative-nitrosative stress.

基于与间苯二酚的亚硝化反应光度法测定水中亚硝酸根

为拓宽光度法测定水中亚硝酸根的线性范围,文章提出了一种基于与间苯二酚的亚硝化反应测定水中亚硝酸根的新方法。在盐酸介质中,亚硝酸根与间苯二酚发生亚硝化反应生成对亚硝基间苯二酚,对亚硝基间苯二酚在pH值为9.97的碱性介质中快速异构化成橙黄色的邻羟基对苯醌单肟,采用分光光度计测定其在351 nm处的吸光度。结果表明,亚硝酸根浓度在0.08 mg/L~1.40 mg/L范围内与吸光度呈良好的线性关系,方法的检出限为0.02 mg/L,用于河水和池塘水中亚硝酸根的测定,回收率在96.3%~102.0%之间,相对标准偏差小于2.35%,测定值与标准方法的参考值吻合。该方法为环境水中亚硝酸根的测定提供了新方法和新思路。

CRI系统亚硝化-厌氧氨氧化的启动调控及性能

为增强人工快速渗滤(CRI)系统对污水中氮素污染物的去除效果,作者分别构建了单级亚硝化CRI反应器(N-CRI)和厌氧氨氧化CRI反应器(A-CRI),探讨了其有效启动调控策略及耦合脱氮性能。结果表明,饥饿14 d后提高进水中NaCl质量浓度至4 g/L,可实现N-CRI反应器亚硝化的高效启动,NO_(2)^(-)-N积累率均值达到98.1%。通过逐步提高水力负荷至1.0 m/d的方式运行45 d后,A-CRI反应器可成功启动厌氧氨氧化,耦合后的N/A-CRI系统对污水中NH_(4)^(+)-N、TN的去除率均值分别达到98.5%、93.1%。菌群结构分析发现,N-CRI反应器内的主要氨氧化菌(AOB)类型为Nitrosomonas和Nitrosospira,主要亚硝酸盐氧化菌(NOB)类型为Nitrospira,饥饿协同NaCl调控可使NOB活性受抑而阻碍其进一步氧化NO_(2)^(-)-N;A-CRI反应器内的主要厌氧氨氧化菌(AAOB)类型为Candidatus Brocadia和Candidatus Kuenenia,其相对丰度的大幅增长为NH_(4)^(+)-N和NO_(2)^(-)-N的同步高效去除创造了条件,为CRI系统脱氮性能的增强提供了一条新途径。

超声辅助提取流苏香竹竹叶黄酮及其对亚硝化反应清除阻断作用

为了提高竹叶黄酮的得率,以流苏香竹叶为研究对象,采用响应面法优化流苏香竹竹叶黄酮超声协同乙醇提取的工艺,并测定流苏香竹叶提取物抗氧化、清除亚硝化物以及阻断亚硝化反应的能力。结果表明,响应面优化超声协同乙醇提取的最佳工艺条件为:乙醇浓度为66.5%,料液比1︰30,超声功率311 W,流苏香竹叶黄酮的得率为37.146 mg/g。生物活性研究表明,流苏香竹叶提取物在一定浓度范围内对羟基自由基和超氧阴离子的清除能力强于L-抗坏血酸(Vc),DPPH自由基清除能力稍弱。对亚硝化物的清除率可达到52.59%,亚硝化反应的阻断率可达到74.75%。相关性分析表明,黄酮类化合物是流苏香竹叶中主要的抗氧化剂,亚硝化物的清除及亚硝化反应的阻断呈高度正相关。该研究发现流苏香竹竹叶黄酮作为多靶点抗癌药物或保健产品的潜力很大,可促进流苏香竹叶高附加值产品的开发。

糖尿病视网膜病变发病机制及潜在治疗靶点研究最新进展

糖尿病(DM)的患病率在全球范围内不断增加,DM的高发促使糖尿病视网膜病变(DR)患者数量激增,DR目前已成为工作年龄人群视力损害和失明的主要原因。DR的进行性发展,涉及许多分子、生物化学机制,而且各种机制之间相互作用,共同影响着视网膜血管及细胞的内环境稳态。随着对DR发病机制的深入研究,越来越多的分子靶点被发现。通过研究DR的发病机制,从中寻找潜在的治疗靶点,对于DR的早期预防、治疗以及防止疾病进一步进展,具有重大临床意义。本文对近年来DR的发病机制及潜在治疗靶点的研究进展进行简要综述。

PCB工业园废水厌氧氨氧化小试研究

本研究搭建了一套前置反硝化-亚硝化-厌氧氨氧化小试实验装置对PCB工业园废水进行了处理,实验结果表明,前置反硝化-亚硝化系统能够完成对PCB废水的除碳以及部分亚硝化处理,经过此套系统处理后的废水满足厌氧氨氧化进水要求。整套小试实验装置在面对变化较大的进水水质的情况下,依然取得了较好的处理效果,平均出水氨氮质量浓度仅为6.5 mg/L,平均出水总氮质量浓度为20.1 mg/L,平均出水COD值为74.7 mg/L。在厌氧氨氧化反应器内出现了耦合反硝化现象,经过厌氧氨氧化处理后的出水硝氮浓度低于亚硝化出水。根据实验结果,作者也提出了利用厌氧氨氧化工艺处理PCB工业园废水的工程实施建议。

温度对好氧颗粒污泥脱氮性能及颗粒稳定性的影响

以乙酸钠与葡萄糖混合基质为碳源,采用间歇式气升内循环反应器(SBAR),以颗粒解体后含有大量丝状菌的污泥为接种污泥,考察了颗粒污泥反应器的启动及温度对好氧颗粒污泥脱氮性能与颗粒稳定性的影响.结果表明,在温度为20℃时,成功实现了颗粒污泥反应器的启动,形成的颗粒结构致密,表面光滑;污泥容积指数(SVI)为70mL/g,平均粒径为3.2mm,平均湿密度为1.029g/mL.当温度直接升高到26℃时,出水NH4+-N由10.6mg/L降为0.2mg/L,同时出现了出水亚硝酸盐的积累,积累率达到93.9%.但是,在温度升高后的47d中,由于胞外多聚物(EPS)中蛋白质与多糖比值的降低,导致颗粒表面的电负性的增加,最终使得颗粒逐渐解体.

pH值对高氨氮废水亚硝化/反亚硝化速率的影响

用两段SBR法处理经稀释的味精废水的过程可分为碳氧化阶段和三个亚硝化/反亚硝化阶段。PH值与废水中的游离氨(FA)和游离亚硝酸(FNA)的浓度相关，是影响脱氮的重要因素。PH值越高，越有利于碳氧化阶段氨氮吹脱效果；亚硝化阶段I、II、III的最佳pH值分别为6.8、8.2、8.2；反亚硝化阶段I、II、III的最佳pH值分别为7.5、8.2、8.2。

琯溪蜜柚果皮提取物抑制亚硝化反应的研究

本实验以乙醇、丙酮和水作为提取剂,对柚皮中的活性物质进行提取,通过正交试验确定出最佳提取条件;在模拟人体胃液环境条件下,采用比色法和紫外光解法分别测定了柚皮提取液对亚硝酸根的清除作用和对亚硝胺合成的阻断作用。结果表明,以乙醇为提取剂的最佳提取条件为:90%乙醇、60℃水浴冷凝回流,提取时间1h;提取液对亚硝胺、亚硝酸钠的最大阻断率和清除率分别为95.5%和91.8%。同时比较了柚皮提取物阻断亚硝胺合成及消除亚硝酸钠的效果。

山竹壳总黄酮抗氧化及抑制亚硝化作用研究

对山竹壳总黄酮的抗氧化作用及对亚硝化反应的抑制作用进行研究。采用超声辅助热水浸提的方法提取山竹壳中的黄酮类化合物,以芦丁为标准物质来测定提取物的总黄酮含量,通过水杨酸法测定山竹壳总黄酮对羟自由基的清除作用、邻苯三酚自氧化法测定山竹壳总黄酮对超氧阴离子自由基的清除作用,以评价山竹壳总黄酮的抗氧化能力;并通过用分光光度法测定山竹壳总黄酮对亚硝酸盐的清除率和对亚硝胺合成的阻断率,以评价山竹壳总黄酮对亚硝化反应的抑制能力。采用超声辅助热水浸提方法提取的山竹壳提取物中总黄酮的含量为42.36%,该类化合物对羟自由基和超氧阴离子自由基具有一定的清除作用,随反应浓度增加清除率增大;在模拟人体胃液的条件下(pH 3.0、温度37℃),山竹壳总黄酮能有效地清除亚硝酸盐和阻断亚硝胺合成,随反应浓度增加清除率和阻断率增大。山竹壳总黄酮具有一定的抗氧化作用及抑制亚硝化反应的作用。

常温条件下短程硝化反硝化生物脱氮研究

对常温条件下生活废水短程硝化反硝化生物脱氮进行了研究.结果表明,在常温(25℃),pH>8.5时,通过提高进水氨氮质量浓度可以使亚硝化率达到80%以上.还对反应过程中pH的变化规律进行了研究,探讨了短程脱氮与全程脱氮相互转化的界面条件,得出游离氨对硝酸菌产生抑制的质量浓度为0.724 mg/L,大于该值时会抑制硝酸菌的生长,而对亚硝酸菌不产生抑制作用.

延时曝气对常温低氨氮SBR亚硝化影响及恢复

常温条件[(22±1)℃]下,采用SBR反应器,探讨延时曝气对常温低氨氮生活污水亚硝化的影响及寻找一种因延时曝气失稳的亚硝化高效恢复策略.结果表明,延时曝气可为NOB创造一个迅速增殖的有利环境,经23d的延时曝气(延迟时间1h)最终使亚硝化系统失稳;且失稳后仅通过限氧无法实现其恢复,而通过增设1h前置厌氧搅拌并缩短曝气时间控制氨氧化率在50%左右,经过60个周期(20d)实现了亚硝化的恢复.

常温条件下短程硝化反硝化生物脱氮影响因素的研究

试验采用SBR工艺研究了不同盐度、NH4^＋-N、pH和温度等因素对含盐废水短程硝化反硝化的影响。发现在20～25℃，pH＞8.5条件下，通过提高进水氨氮浓度可以使亚硝化率[NO2^-／（NO2^-＋NO3^-）]达到90％以上。实验证明，亚硝酸菌有较高的耐盐性，能在高盐环境中保持良好的活性。

污水短程脱氮工艺中亚硝酸盐积累的影响因素

采用主要由厌氧-好氧-缺氧构成的短程脱氮工艺,进行了常温条件下处理生活污水的实验.分析了DO、游离氨（FA）等因素对亚硝酸盐积累的影响.结果表明,DO是影响短程硝化的主要因素,控制好氧1区的DO在1.5~2.5mg/L、好氧2区的DO在0.5-1.0mg/L,可以实现稳定的亚硝酸盐的积累,氨氮去除率达到90%.对氨氧化菌（AOB）进行T-RFLP群落分析表明,该工艺运行中的AOB优势菌种为Nitrosomonas oligotropha culster.

甲基橙亚硝化极谱法测定亚硝酸根

研究了甲基橙亚硝化产物的极谱波行为 ,提出了亚硝化极谱法测定亚硝酸根的灵敏极谱波新体系。在 0 .6mol/L 盐酸中 ,甲基橙与 NO-2 的亚硝化反应产物在极谱仪上于 - 0 .31 V( vs.SCE)可获得灵敏的极谱波。导数波高与亚硝酸根浓度在 1 .0 9× 1 0 -7～ 1 .0 9× 1 0 -5mol/L范围内成正比 ,检出限为 6.52× 1 0 -8mol/L。研究了极谱波行为及反应机理。