1-MCP对‘绿宝石’梨采后成熟衰老期间H2O2含量及其相关酶活性的影响

为探讨1-甲基环丙烯(1-MCP)对梨果实采后成熟衰老过程中过氧化氢(H2O2)代谢的作用,试验以‘绿宝石’梨为材料,用1.0 μL/L 1-MCP密封处理24 h,空气密封为对照,研究1-MCP对‘绿宝石’梨室温(25±2)℃贮藏过程中果实硬度、可溶性同形物含量(SSC)、呼吸速率、H2O2含量、抗氧化酶活性[超氧化...     

水杨酸处理对桃贮藏期间活性氧代谢的影响

桃果实采后用浓度为 0 g·L- 1、0 3g·L- 1的水杨酸 (SA)溶液浸果 15min ,然后分别放置在 2 3～ 2 5℃和 ( 10± 1)℃条件下贮藏 与水浸的对照相比 ,SA处理的果实在贮藏期间超氧阴离子 (O 2 )生成的速率都加快了 ;室温中桃的SOD活性受到抑制 ,低温中桃的SOD活性增加 ;果肉组织的H2 O2 含量和CAT活性都很快增加 ,第 2d有一个高峰 ,然后下降 ,4d后与对照差异不大 ;过氧化酶 (POD)活性在前 4d大大受到抑制 ,没有出现对照那样的高峰 ,以后有略高于对照的趋势     

Reductive cyclotrimerization of carbon monoxide to the deltate dianion by an organometallic uranium complex

Despite the long history of the Fischer-Tropsch reaction, carbon monoxide has proven remarkably resistant to selective homologation under mild conditions. Here, we find that an organouranium(III) complex induces efficient reductive trimerization of carbon monoxide at room temperature and pressure. The result is a triangular, cyclic C3O(2-)3, or deltate, dianion held between two uranium(IV) units. The bonding within the C3O(2-)3 unit and its coordination to the two U centers have been analyzed by x-ray diffraction and density functional theory computational studies, which show a stabilizing C-C agostic interaction between the C3 core and one U center. Solution nuclear magnetic resonance studies reveal a rapid equilibration of the deltate unit between the U centers.     

A synthetic nickel electrocatalyst with a turnover frequency above 100,000 s⁻¹ for H₂ production

Reduction of acids to molecular hydrogen as a means of storing energy is catalyzed by platinum, but its low abundance and high cost are problematic. Precisely controlled delivery of protons is critical in hydrogenase enzymes in nature that catalyze hydrogen (H(2)) production using earth-abundant metals (iron and nickel). Here, we report that a synthetic nickel complex, [Ni(P(Ph)(2)N(Ph))(2)](BF(4))(2), (P(Ph)(2)N(Ph) = 1,3,6-triphenyl-1-aza-3,6-diphosphacycloheptane), catalyzes the production of H(2) using protonated dimethylformamide as the proton source, with turnover frequencies of 33,000 per second (s(-1)) in dry acetonitrile and 106,000 s(-1) in the presence of 1.2 M of water, at a potential of -1.13 volt (versus the ferrocenium/ferrocene couple). The mechanistic implications of these remarkably fast catalysts point to a key role of pendant amines that function as proton relays.     

Binuclear ion containing nitrogen as a bridging group

A binuclear ion ([NH(3))5RuN(2)Ru(NH(3))(5)](5)+ is formed by the direct reaction of N(2) with an aqueous solution of (NH(3))(5)RuOH(2)(2+) at room temperature. The binuclear ion is also formed by the reversible reaction of (NH(3))5RuOH(2)(2+) with (NH(3))(5)RuN(2)(2+). Solid [(NH(3))(5)RuN(2)Ru(NH(3))(5)] (BF(4))(4) has been prepared, and its ultraviolet and infrared spectra are reported.     

On the Quantum Nature of the Shared Proton in Hydrogen Bonds

The relative influence of thermal and quantum fluctuations on the proton transfer properties of the charged water complexes H5O2+ and H3O2- was investigated with the use of ab initio techniques. These small systems can be considered as prototypical representatives of strong and intermediate-strength hydrogen bonds. The shared proton in the strongly hydrogen bonded H5O2+ behaved in an essentially classical manner, whereas in the H3O2- low-barrier hydrogen bond, quantum zero-point motion played a crucial role even at room temperature. This behavior can be traced back to a small difference in the oxygen-oxygen separation and hence to the strength of the hydrogen bond.     

A thiosulfate shunt in the sulfur cycle of marine sediments

The oxidation of sulfide, generated by bacterial sulfate reduction, is a key process in the biogeochemistry of marine sediments, yet the pathways and oxidants are poorly known. By the use of (35)S-tracer studies of the S cycle in marine and freshwater sediments, a novel shunt function of thiosulfate (S(2)O(3)(2-)) was identified. The S(2)O(3)(2-) constituted 68 to 78 percent of the immediate HS(-)-oxidation products and was concurrently (i) reduced back to HS(-), (ii) oxidized to SO(4)(2-), and (iii) disproportionated to HS(-) + SO(4)(2-). The small thiosulfate pool is thus involved in a dynamic HS(-) - S(2)O(3)(2-) cycle in anoxic sediments. The disproportionation of thiosulfate may help account for the large difference in isotopic composition ((34)S/(32)S) of sulfate and sulfides in sediments and sedimentary rocks.     

基于Nafion/天青A/纳米金层层自组装固定酶的过氧化氢生物传感器

[目的]明确基于Nafion、天青A、纳米金层层自组装固定酶制备过氧化氢生物传感器的可行性。[方法]先利用静电吸附和自组装技术将Nafion、天青A、纳米金修饰到金电极表面,然后利用纳米金吸附辣根过氧化物酶(HRP),制备过氧化氢生物传感器。采用循环伏安法和计时电流法考察该传感器的性能。[结果]在测试溶液pH值5.5、工作电位-0.3~-0.2 V、扫速100 mV/s、检测温度25℃条件下,该传感器具有良好的生物催化活性,还原峰电流与H2O2浓度在2.0×10-6~1.6×10-3mol/L范围内呈良好的线性关系,检出限为7.62×10-7mol/L。该传感器稳定性好,抗干扰力强,制备方法简单,成本低廉,对H2O2有快速灵敏的响应。[结论]该研究制备的过氧化氢生物传感器灵敏度较高,检测范围宽,检出限较低。     

Chemical and spectroscopic evidence for an FeV-oxo complex

Iron(V)-oxo species have been proposed as key reactive intermediates in the catalysis of oxygen-activating enzymes and synthetic catalysts. Here, we report the synthesis of [Fe(TAML)(O)]- in nearly quantitative yield, where TAML is a macrocyclic tetraamide ligand. Mass spectrometry, M?ssbauer, electron paramagnetic resonance, and x-ray absorption spectroscopies, as well as reactivity studies and density functional theory calculations show that this long-lived (hours at -60 degrees C) intermediate is a spin S = 1/2 iron(V)-oxo complex. Iron-TAML systems have proven to be efficient catalysts in the decomposition of numerous pollutants by hydrogen peroxide, and the species we characterized is a likely reactive intermediate in these reactions.     

Effects of 1-Methylcyclopropene on NO Content, NOS Activity, and H2O2 Content in Postharvest Suli Pears

Studies were conducted over the effects of 1-methylcycolpropene (1-MCP) treatment on postharvest life of Suli pears (Pyrus bretschneideri Rehd.) stored at room and cold temperatures on nitric oxide (NO), nitric oxide synthase (NOS)activity, and hydrogen dioxide (H2O2). Results showed that the 1-MCP treatment had little effect on total soluble solids (TSS) at both room and cold temperatures. 1-MCP delayed softening of Suli pear fruits, decreased respiratory rate and H2O2 accumulation, and increased NO and NOS activity at room temperature storage, while the effect of cold temperature storage was relatively inferior. There was a significant positive correlation between NOS activity and NO content. It is concluded that 1-MCP had effects on endogenous NO content and accumulation of H2O2. Similarly, H2O2 acting as a signaling molecule via regulating NO level affects the ripening and senescence of Suli pears.     

双氧水对水稻秸秆中氮和硫的脱除效果

利用双氧水(H_2O_2)对水稻秸秆中的氮、硫进行脱除,重点考察了H_2O_2用量以及温度对脱除效果的影响。结果表明,H2O2用于脱除水稻秸秆中的氮、硫效果良好,同时对秸秆的主体结构影响较小,其脱除氮、硫的最佳条件为H_2O_2体积分数3.0%、温度50℃。     

Boron-Oxygen Polyanion in the Crystal Structure of Tunellite

The crystal structure of tunellite, SrO.3B(2)O(3).4H(2)O, with infinite sheets of composition n[B(6)O(9)(OH)(2)](2-), has cations and water molecules in the spaces within the sheets. Adjacent sheets are held together by hydrogen bonding through the water molecules. The boron-oxygen polyanions provide the first example in hydrated borate crystals of one oxygen linked to three borons.     

Efficient oxidative dechlorination and aromatic ring cleavage of chlorinated phenols catalyzed by iron sulfophthalocyanine

An efficient method has been developed for the catalytic oxidation of pollutants that are not easily degraded. The products of the hydrogen peroxide (H(2)O(2)) oxidation of 2,4,6,-trichlorophenol (TCP) catalyzed by the iron complex 2,9,16,23-tetrasulfophthalocyanine (FePcS) were observed to be chloromaleic, chlorofumaric, maleic, and fumaric acids from dechlorination and aromatic cycle cleavage, as well as additional products that resulted from oxidative coupling. Quantitative analysis of the TCP oxidation reaction revealed that up to two chloride ions were released per TCP molecule. This chemical system, consisting of an environmentally safe oxidant (H(2)O(2)) and an easily accessible catalyst (FePcS), can perform several key steps in the oxidative mineralization of TCP, a paradigm of recalcitrant pollutants.     

Addition radicals formed by hydroxyl radical bombardment of uracil

Direct addition of O-H radicals at room temperature to the carbon No.5 of the uracil ring has been proved by measurement of the proton hyperfine structure in the electron spin resonance of the resulting uracil + O-H radicals. Upon addition of the OH, the H originally bound to carbon No. 5 shifts to No. 6, thus forming a methylene group at carbon No. 6, with the two protons having equivalent coupling of 28 gauss. The spin density on carbon No. 5 is O.64. The radicals were produced when powdered samples of uracil were subjected to a low-velocity beam of O-H radicals coming from either hydrogen peroxide or water vapor under reduced pressure and subjected to an electric discharge.     

A solid sulfur cathode for aqueous batteries

Because of its high resistivity and subsequent low electroactivity, sulfur is not normally considered a room-temperature battery cathode. An elemental sulfur cathode has been made with a measured capacity of over 900 ampere.hours per kilogram, more than 90 percent of the theoretical storage capacity of solid sulfur at room temperature, accessed by means of a lightweight, highly conductive, aqueous polysulfide interface through the electrocatalyzed reaction S + H(2)O + 2e(-) --> HS(-) + OH(-). This solid sulfur cathode was first used in a battery with an aluminum anode for an overall discharge reaction 2Al + 3S + 3OH(-) + 3H(2)O --> 2Al(OH)(3) + 3HS(-), giving a cell potential of 1.3 volts. The theoretical specific energy of the aluminum-sulfur battery (based on potassium salts) is 910 watt.hours per kilogram with an experimental specific energy of up to 220 watt.hours per kilogram.     

不同提取方法下茶园土壤可溶性有机氮含量差异

以相似地形条件、相同成土母质和土壤类型的两个品种(黄旦和福云6号)茶园生态系统为研究对象,采用H2O(室温)、H2O(70℃)和KCl(2 mol.L-1)3种提取方法研究两个品种茶园土壤可溶性有机氮(SON)含量差异.结果表明,茶园不同土层3种提取方法的土壤SON含量间呈显著或极显著差异,SON含量大小均表现为:KCl(2 mol.L-1)>H2O(70℃)>H2O(室温);H2O(室温)、H2O(70℃)、KCl(2 mol.L-1)提取测定的黄旦和福云6号茶园上层(0-15 cm)土壤SON含量分别比下层(15-30 cm)高9.62%、17.93%、11.64%和36.57%、46.23%、25.54%,垂直差异达显著或极显著水平;H2O(70℃)和KCl(2 mol.L-1)提取测定的黄旦茶园上层土壤SON含量分别比福云6号上层高17.44%和7.88%,差异达显著水平.可见,茶园土壤SON含量因提取剂及茶树品种的不同而差异明显.     

Hydrogen storage in microporous metal-organic frameworks

Metal-organic framework-5 (MOF-5) of composition Zn4O(BDC)3 (BDC = 1,4-benzenedicarboxylate) with a cubic three-dimensional extended porous structure adsorbed hydrogen up to 4.5 weight percent (17.2 hydrogen molecules per formula unit) at 78 kelvin and 1.0 weight percent at room temperature and pressure of 20 bar. Inelastic neutron scattering spectroscopy of the rotational transitions of the adsorbed hydrogen molecules indicates the presence of two well-defined binding sites (termed I and II), which we associate with hydrogen binding to zinc and the BDC linker, respectively. Preliminary studies on topologically similar isoreticular metal-organic framework-6 and -8 (IRMOF-6 and -8) having cyclobutylbenzene and naphthalene linkers, respectively, gave approximately double and quadruple (2.0 weight percent) the uptake found for MOF-5 at room temperature and 10 bar.     

Ammonium micas: possible sources of atmospheric ammonia and nitrogen

Ammonium muscovite, NH(4)Al(2)AlSi(3)O(10)(OH)(2), and ammonium phlogopite, NH(4)Mg(3)AlSi(3)O(10)(OH)(2), have been synthesized hydrothermally at gas pressures of 2 kilobars and temperatures between 550 degrees and 730 degrees C. Both micas are stable only in environments of high ammonia fugacity. Ammonia or nitrogen, or both, are released by thermal decomposition, cation exchange, or oxidation. The ammonia : nitrogen ratio in the gas depends primarily on the hydrogen fugacity and the temperature of the environment. Calculations show that, even in a predifferentiated Earth, nitrogen may have predominated. The total amount of nitrogen present on the surface of Earth could be accounted for by the decomposition of a layer of ammonium muscovite 170 meters thick.     

Efficient epoxidation of olefins with >/=99% selectivity and use of hydrogen peroxide

Epoxides are an important class of industrial chemicals that have been used as chemical intermediates. Catalytic epoxidation of olefins affords an interesting production technology. We found a widely usable green route to the production of epoxides: A silicotungstate compound, [gamma-SiW10O34(H2O)2]4-, is synthesized by protonation of a divacant, lacunary, Keggin-type polyoxometalate of [gamma-SiW10O36]8- and exhibits high catalytic performance for the epoxidation of various olefins, including propylene, with a hydrogen peroxide (H2O2) oxidant at 305 kelvin. The effectiveness of this catalyst is evidenced by >/=99% selectivity to epoxide, >/=99% efficiency of H2O2 utilization, high stereospecificity, and easy recovery of the catalyst from the homogeneous reaction mixture.     

木质素磺酸盐碱性过氧化氢降解及结构表征

通过表征受碱性过氧化氢降解的木质素磺酸盐,探索高效低耗的木质素降解条件。木质素磺酸盐与含有H2O2的0.5、1.0、2.0 mol/L的NaOH溶液分别在90、170℃下反应2 h。结果表明:碱性过氧化氢处理后木质素磺酸盐的Mw(重均相对分子质量)和Mn(数均相对分子质量)降低,而在170℃,1 mol/L NaOH溶液条件下获得最大程度的降解。木质素磺酸盐的相对分子质量在降解后分布相对集中,这表明木质素磺酸盐可直接用于开发木质素基材料而无需进一步分离。用碱性过氧化氢降解后,甲氧基摩尔分数降低。在170℃、2 mol/L NaOH溶液条件下4步加入过氧化氢,降解得到的木质素甲氧基摩尔分数下降57.4%。碱性硝基苯氧化的结果也表明在170℃下用2 mol/L NaOH溶液和4步添加H2O2处理后会得到最低的香草醛和香草酸产率,表明该条件下非浓缩的木质素结构被有效破坏。FTIR结果显示木质素的芳香结构消失。木质素磺酸盐利用碱性过氧化物降解,最佳条件是在2 mol/L NaOH溶液和170℃条件下,分4步添加H2O2。