One-dimensional copper phosphonates containing μ-halide, μ-pyridyl N-oxide and phosphonate bridging ligands

This paper reports the syntheses and characterization of four copper phosphonates with chain structures based on (2-pyridyl-N-oxide)phosphonate, namely, [Cu₂X₂(C₅H₄NOPO₃)₂][Cu(H₂O)₆] · 2H₂O [X = Cl (1), Br (2)] and CuX(C₅H₄NOPO₃H) · H₂O [X = Cl (3), Br (4)]. Compounds 1 and 2 are isostructural and show a chain structure where Cu(1) and Cu(2) are triply bridged by halide, oxygen donor of the pyridyl N-oxide and O–P–O group. The [Cu(H₂O)₆]²⁺ serves as a charge-balancing cation and locate between the chains together with the water molecules. Compounds 3 and 4 are also isostructural. In these cases, one of the three phosphonate oxygen atoms is protonated, thus leading to a neutral chain structure which is very similar to the anionic chains in compounds 1 and 2. Magnetic studies of compounds 1–4 reveal that antiferromagnetic interactions are mediated between the copper ions.     

Selective C-H bond activation of arenes catalyzed by methylrhenium trioxide

Arenes, in glacial acetic acid, are oxidized to para-benzoquinones by hydrogen peroxide when methylrhenium trioxide (CH₃ReO₃ or MTO) is used as a catalyst. In some cases an intermediate hydroquinone was also obtained in lower yield. Oxidation of the methyl side chains of various methylbenzenes did not occur. The active catalyst species are the previously-characterized η²-peroxorhenium complexes, CH₃Re(O)₂(η²-O₂) and CH₃Re(O)(η²-O₂)₂H₂O). Separate tests showed that hydroquinones and phenols are oxidized by H₂O₂-MTO more rapidly than the simple arenes; in the proposed mechanism they are intermediate products. Higher conversions were found for the more highly-substituted arches, consistent with their being the most reactive species toward the electrophillically-active peroxide bound to rhenium. High conversions of the less substituted members of the series were not achieved, reflecting concurrent deactivation of MTO-peroxide, a process of greater import for the more slowly-reacting substrates.     

草原土壤N2O释放及全球变暖影响下土壤养分变化的反馈效应

对草原土壤N₂O释放及其受全球变暖土壤养分变化的影响研究表明,以沼泽泥炭土N₂O释放量最大,生长季节为1.3～12.2kgN·hm^-2·a^-1,其次灰壤土,为1.5～2.4kgN·hm^-2·a^-1,酸性棕壤最小,为0～3.2kgN·hm^-2·a^-1;N₂O的释放层灰壤土在0～5cm,其它2种土壤为0～10cm;施肥试验表明,N、P肥在生长季节对土壤N₂O释放量影响不显着,但在生长季末期,N肥对酸性棕壤及灰壤土N₂O影响显着,施肥后第3天酸性棕壤由对照的1.3提高到44.2kgN·hm^-2·a^-1,灰壤土则由对照的1.9提高到31.1kgN·hm^-2·a^-1,说明全球变暖对土壤有机质分解的影响不会诱发N₂O释放量的大幅度增加.     

One-dimensional polymeric chlorocadmate(II) systems of N-methylpiperazinium and N,N′-dimethylpiperazinium compounds: synthesis, structural and thermal properties

The chlorocadmate(II) systems of (H₂me₂pipz)[Cd₂Cl₆(H₂O)₂] (1) and (H₂mepipz)₂[Cd₃Cl₁₀(H₂O)] (2) (L = me₂pipz = N,N′-dimethylpiperazine; L′ = mepipz = N-methylpiperazine) were prepared and their structural and thermal properties investigated. Compound 1 is monoclinic, space group P2₁/c, A = 7.664(1), B = 7.472(4), C = 15.347(1) Å, β = 99.468(7)°, Z = 2, R = 0.024. The crystal structure consists of organic cations and infinite one-dimensional chains of [CdCl₃(H₂O)]_n³⁻ anions. Each Cd atom is octahedrally surrounded by bridged and terminal chlorine atoms and by a water molecule, which is in trans position with respect to the terminal chlorine atom. Inter- and intrachain hydrogen bond interactions between the terminal chlorine atoms and the water molecules contribute to the crystal packing. Compound 2 is orthorhombic, space group Cmc2₁, A = 15.286(3), B = 13.354(3), C = 13.154(3) Å, R = 0.023. The crystal structure consists of organic dications and infinite chains of [Cd₂Cl₆(CdCl₄H₂O]_n⁴⁻ units running along the [001] axis. Each unit is formed of regularly alternate six-coordinated Cd atoms, one of them linking one pentacoordinated Cd atom which completes its coordination througha water molecule. A strong hydrogen bond interaction involving the organic dication and the inorganic chain contributes to the crystal packing. Differential hydrogen bond interaction involving the organic dication and the inorganic chain contributes to the crystal packing. Differential scanning calorimetry measurements did not show the presence of any structural phase transitions. The structures are compared with those of (H₂pipz)[Cd₂Cl₆(H₂O)₂] (3), (H₂mepipz)[Cd₂Cl₆(H₂O)₂]·H₂O (4) and (H₂mepipz)[Cd₂Cl₆] (5) (L = pipz = piperazine, L′ = mepipz = N-ethylpiperazine).     

模拟酸雨对南亚热带典型森林土壤N2O排放的影响

基于长期模拟酸雨森林样地,利用箱式法同步测定了不同酸雨强度处理下森林土壤N2O排放通量,研究了模拟酸雨对我国南亚热带针阔叶混交林和季风常绿阔叶林两种代表性森林土壤N2O排放的影响.结果 表明:连续5年(2014-2018年)观测周期内,两种林型土壤N2O排放通量在各模拟酸雨处理下均表现出明显的季节变化特征,湿季排放通量...     

Hippuric acid and benzoic acid inhibition of urine derived N2O emissions from soil

Atmospheric concentrations of the greenhouse gas nitrous oxide (N₂O) have continued to rise since the advent of the industrial era, largely because of the increase in agricultural land use. The urine deposited by grazing ruminant animals is a major global source of agricultural N₂O. With the first commitment period for reducing greenhouse gas emissions under the Kyoto Protocol now underway, mitigation options for ruminant urine N₂O emissions are urgently needed. Recent studies showed that increasing the urinary concentration of the minor urine constituent hippuric acid resulted in reduced emissions of N₂O from a sandy soil treated with synthetic bovine urine, due to a reduction in denitrification. A similar effect was seen when benzoic acid, a product of hippuric acid hydrolysis, was used. This current laboratory experiment aimed to investigate these effects using real cow urine for the first time. Increased concentrations of hippuric acid or benzoic acid in the urine led to reduction of N₂O emissions by 65% (from 17% to <6% N applied), with no difference between the two acid treatments. Ammonia volatilization did not increase significantly with increased hippuric acid or benzoic acid concentrations in the urine applied. Therefore, there was a net reduction in gaseous N loss from the soil with higher urinary concentrations of both hippuric acid and benzoic acid. The results show that elevating hippuric acid in the urine had a marked negative effect on both nitrification and denitrification rates and on subsequent N₂O fluxes. This study indicates the potential for developing a novel mitigation strategy based on manipulation of urine composition through ruminant diet.     

几种旱地农作物在农田N2O释放中的作用及环境因素的影响

用封闭箱法原位观测几种旱田N₂O的排放通量,并与裸地N₂O通量比较,评价植物在农田N₂O释放中的作用。田间观测与室内模拟实验结合,考察环境因子对N₂O通量的影响。结果表明1d内大豆田N₂O通量有两个释放高峰,而菠菜田和春小麦田只有1个释放高峰。种植大豆较大地提高了农田N₂O的排放通量。农田裸地为一较弱的N₂O释放源,且在1年的一定时期内表现为大气N₂O的汇。光照变化对植物N₂O通量影响很大,在较弱的光照条件下,植物释放N₂O的通量较高。     

Two new multi-cobalt-containing heteropolyoxotungstates

Two new multi-cobalt-containing polyoxotungstates K₄Na₆Co₂(H₂O)₁₂{Co(H₂O)₄[Co₂(H₂O)₁₀Co₄(H₂O)₂(B--SiW₉O₃₄)₂]₂} · 40H₂O (1) and K₁₀Na₂[Co₄(H₂O)₂(GeW₉O₃₄)₂] · 20H₂O (2) have been obtained by the routine synthetic reactions in aqueous solution. The polyoxoanion framework of 1 consists of two sandwich-type polyoxoanions [Co₄(H₂O)₂(B--SiW₉O₃₄)₂]¹²⁻ connected together by a [CoO₂(H₂O)₄] cluster to constitute the sandwich dimer, and then, four isolated Co(H₂O)₅ cations coordinate to the dimer through four μ₂-O atoms. The polyoxoanion 2 is isomorphic to the sandwich-type polyoxoanion [Co₄(H₂O)₂(B--SiW₉O₃₄)₂]¹²⁻ in 1. The magnetic property of compound 1 has been studied by measuring its magnetic susceptibility in the temperature range 2.0–300.0 K, indicating the existence of intramolecular ferromagnetic Co–Co interactions, and, the electrochemical properties of 1 and 2 are detected in the pH 4 buffer solution.     

广州地区晚稻田 CH4和N2O 的排放通量及其影响因素

用密闭箱法同时研究了广州地区晚稻田CH₄和N₂O的排放通量。结果表明,连续淹水、常规连作和水旱轮作等3种处理的CH₄平均排放通量分别为1.763、2.84和0.36mg·m^-2·h^-1,而N₂O的平均排放通量分别为6.74、11.69和55.07μgN₂O-N·m^-2·h^-1,表明稻田连续淹水显著增加CH₄的排放而降低N₂O的排放。水旱轮作降低CH₄排放而提高N₂O的排放,说明稻田CH₄和N₂O排放之间存在着消长关系。讨论了这2种温室气体排放的影响因素,并初步分析了它们对温室效应的相对贡献。     

田间大豆植株N2O通量的测定及光照的影响

采用封闭式箱法,在田间自然状况下对大豆植株N₂O通量进行了测定.结果表明,在主要生育期内,大豆植株N₂O通量有2个释放高峰,分别位于苗期和开花结荚期.大豆植株N₂O通量的昼间变化模式基本上为上午有1个释放高峰,而下午有一个释放低谷.施肥和对照小区N₂O平均通量分别为2.27和1.28μgN₂Om^-2·h^-1.在较强的光照条件下(10⁴lx数量级),大豆植株N₂O通量较低,甚至可吸收大气中的N₂O,而在较弱光照条件下(10³～10²lx数量级),大豆植株N₂O通量较高.     

青藏高原高寒草原近地表圈层N2O梯度及交换特征

深入了解N2O在不同生态系统土壤及大气中产生和交换特征对于全球气候变化研究具有重要意义.本研究重点探讨N2O在高寒草原近地表圈层中的产生及迁移过程机制.于2000年7月至2001年7月在青藏高原高寒草原地区从土壤1.5 m深到大气中32 m高度10个层次梯度进行N2O浓度变化的观测.结果显示,土壤和大气中N2O浓度均有明显的变化特征.大气中各个层次N2O的浓度都低于土壤中N2O浓度,此浓度差异直接导致了该地区高寒草原土壤向大气中排放N2O气体,其平均排放通量为0.05×10-4μmo1.m-2.s-1,但是在实验点上全年的观测中,N2O气体排放并没有表现出明显的季节性变化特征.土壤中N2O浓度随深度增加而不断升高,浓度最高值出现在1.5 m深处.进一步的分析表明,N2O浓度随深度递增主要是由环境因子中同样递增的土壤湿度所引起的.大气中不同梯度上N2O气体没有明显的浓度差异.近地表各个圈层中N2O浓度在季节上有非常相似的变化特征,即N2O高浓度均出现在入秋和深冬时节.除了N2O浓度变化在各个圈层之间显著相关以外,表层土壤中N2O浓度也与N2O排放变化有明显的相关关系,这表明浓度的差异是导致N2O气体排放变化的最直接因素.近地表土壤中N2O气体是土壤表层N2O气体排放的直接源泉,并且深层土壤中的N2O气体浓度高于浅层土壤,由此我们可以认定土壤中N2O气体通过微生物作用产生以后,由于浓度差异导致从深层土壤到浅层土壤的逐步扩散,最后经地表排放到大气当中去.     

Carbohydrate Analysis of the B2 Bradykinin Receptor from Rat Uterus

Abstract: The B₂ bradykinin receptor purified from rat uterus has an apparent molecular mass of 81 kDa. This is higher than the value of 42 kDa estimated from the sequence data of rat and human B₂ receptors. Carbohydrate analysis of the rat B₂ bradykinin receptor indicated that it was a sialoglycoprotein with three N-linked complex oligosaccharide side chains. This was consistent with the sequence, which has three potential glycosylation sites. The receptor did not appear to possess O-linked carbohydrate side chains. Removal of the N-linked carbohydrates with endo-β- N -acetylglucosaminidase yielded a core protein of 42–44 kDa. The presence of these N-linked carbohydrates explains the discrepancy between the molecular size of the purified receptor protein and that estimated from the sequence. The sequence of the rat receptor suggests an isoelectric point of about pH 7.0, but the purified receptor had an isoelectric point of pH 4.5–4.7. Sialic acid residues on the N-linked side chains are likely to be responsible for the acidic nature of the rat receptor. Carbohydrate does not appear to play a role in ligand-receptor interactions, as deglycosylation did not alter the affinity of the B₂ bradykinin receptor for bradykinin or the B₂-selective antagonist HOE-140.     

The effect of renal vasodilation and hypotonic volume expansion on water excretion in dogs after anesthesia and surgery

The possible effects of renal vasoconstriction from anesthesia and surgery on water excretion after hypotonic volume expansion (HVE) were studied in 18 well conditioned anesthetized dogs, with and without the infusion of phenoxybenzamine and acetylcholine into the renal artery of the cannulated kidney. In 6 dogs (Group 1 - Control) whose renal artery was infused with isosmotic saline, HVE resulted in a bilateral increase in GFR and UV (p < .05). ERPF, Cosm, C_H2O, U_NaV, U_KV, RBF, RVR and MAP did not change significantly. In 6 other dogs (Group 2), whose cannulated kidney was infused with phenoxybenzamine 50 μg/min before and during HVE, GFR increased on the infused side while CH₂O and UV increased bilaterally (p < .05). ERPF, Cosm, U_NaV, U_KV, RBF, RVR and MAP were not affected significantly. The addition of ADH, 2 mu/min into the phenoxybenzamine infusate, decreased ERPF, RBF and RVR bilaterally and CH₂O on the infused side (p < .05). It had no effect upon GFR, Cosm, U_NaV, U_KV and MAP. In another 6 dogs, (Group 3), whose cannulated renal artery was infused with acetylcholine (20 μg/min) before and during HVE, C_H2O, UV and RVR increased bilaterally (p < .05). ERPF and RBF decreased bilaterally (p < .05), whereas GFR, Cosm, U_NaV and MAP were unaffected. U_KV decreased on the infused side (p < .05). The addition of ADH (2 mu/min)_into the acetylcholine infusate, decreased C_H2O bilaterally and increased Cosm and U_KV on the control side (p < .05). It had no effect on ERPF, GFR, UV, U_NaV, RBF, RVR and MAP. These observations suggest that anesthesia and surgery produce renal vasoconstriction and this together with increased ADH release, interfere with water excretion by the kidney. Previous renal vasodilation prevents these influences of anesthesia and surgery.     

Convergence in the relationship of CO2 and N2O exchanges between soil and atmosphere within terrestrial ecosystems

Ecosystem CO₂ and N₂O exchanges between soils and the atmosphere play an important role in climate warming and global carbon and nitrogen cycling; however, it is still not clear whether the fluxes of these two greenhouse gases are correlated at the ecosystem scale. We collected 143 pairs of ecosystem CO₂ and N₂O exchanges between soils and the atmosphere measured simultaneously in eight ecosystems around the world and developed relationships between soil CO₂ and N₂O fluxes. Significant linear regressions of soil CO₂ and N₂O fluxes were found for all eight ecosystems; the highest slope occurred in rice paddies and the lowest in temperate grasslands. We also found the dominant role of growing season on the relationship of annual CO₂ and N₂O fluxes. No significant relationship between soil CO₂ and N₂O fluxes was found across all eight ecosystem types. The estimated annual global N₂O emission based on our findings is 13.31 Tg N yr⁻¹ with a range of 8.19–18.43 Tg N yr⁻¹ for 1980–2000, of which cropland contributes nearly 30%. Our findings demonstrated that stoichiometric relationships may work on ecological functions at the ecosystem level. The relationship of soil N₂O and CO₂ fluxes developed here could be helpful in biogeochemical modeling and large-scale estimations of soil CO₂ and N₂O fluxes.     

Unusual glycoconjugates in the oesophagus of a tilapine polyhybrid

The aim of this work is to elucidate the glycoconjugate composition of the secretory products of the oesophageal mucous cells in a tilapine polyhybrid. Lectin histochemistry gave evidence of the presence of β-galactose, α-N-acetylgalactosamine and sialic acid residues in the terminal position. The majority of sialic acid belongs to short side chains; a few sialic acid residues are acetylated at the C₇ and/or C₈ and/or C₉ level. The heterogeneity of the carbohydrate chains may mask potential receptor sites for micro-organisms and hamper the formation of multiple bonds.     

若尔盖高原沼泽湿地N2O排放通量研究

应用静态箱/气相色谱法,测定了若尔盖高原沼泽N₂O排放能量,测定期为该地植物生长期,即2004年4月末至10月初。结果表明,若尔盖高原沼泽湿地N₂O排放通量平均值为0.010mg·m^-2h^-1,最大值为0.079mg·m^-2h^-1,最小值为-0.051mg·m^-2h^-1。高峰排放期为5月,最低排放期为地表水深最大的6月。沼泽湿地N₂O排放通量季节变化与沼泽湿地水深呈负相关关系。沼泽湿地N₂O排放通量日变化与大气温度呈正相关关系,排放高值出现在午后。若尔盖高原沼泽湿地在植物生长期的年排放总量约为0.159Gg·a^-1。     

Staining Tissue of the Central Nervous System with Luxol Fast Blue and Neutral Red

The tissue is fixed in 10% neutral saline formalin for 1 day to 3 wk depending on the size of the block, dehydrated and embedded in paraffin. The sections are stained at 57° C for 2 hr, then at 22° C for 30 min, in a 0.0125% solution of Luxol fast blue in 95% alcohol acidified by 0.1% acetic acid. They are differentiated in a solution consisting of: Li₂CO₃, 5.0 gm; LiOH-H₂O, 0.01 gm; and distilled water, 1 liter at 0-1° C, followed by 70% alcohol, and then treated with 0.2% NaHSO₃. They are soaked 1 min in an acetic acid-sodium acetate buffer 0.1 N, pH 5.6, then stained with 0.03% buffered aqueous neutral red. Sections are washed in distilled water, 1 sec, then treated with the following solution: CuSO₄·5H₂O, 0.5 gm; CrK(SO₄)₂·12H₂O, 0.5 gm; 10% acetic acid, 3 ml; and distilled water, 250 ml. Dehydration, clearing and covering complete the process. Myelin sheaths are stained bright blue; meninges and the adventitia of blood vessels are blue; red blood cells are green. Nissl material is stained brilliant red; axon hillocks, axis cylinders, ependyma, nuclei and some cytoplasm of neuroglia, media and endothelium of blood vessels are pink.     

喀斯特石漠化地区土壤温室气体的地气交换特征

利用密闭箱-气相色谱法于2006～2007年对黔中喀斯特地区土壤二氧化碳、氧化亚氮和甲烷的释放通量进行原位观测,研究我国南方喀斯特石漠化地区土壤温室气体地气交换特征.结果表明:喀斯特石漠化地区土壤是大气CO₂、N₂O的释放源,CH₄的吸收汇.土壤CO₂的释放通量介于450.8±50.8～1281.3±214.7 mg·m^-2·h^-1在之间,夏秋季节高于冬春季节;N₂O的释放通量介于-25.4±4.1～105.8±31.2μg·m^-2·h^-1之间,在夏季最高,在9月、11月和12月出现土壤对大气N₂O的吸收;全年CH₄交换通量介于-0.27±0.18～0.81±0.26 mg·m^-2·h^-1之间,随季节的变化不明显.气候条件对土壤CO₂和CH₄交换通量的影响较小,土壤水分对N₂O释放通量的影响效应在不同的季节不同.相关分析结果显示,土壤N₂O和CH₄地气交换通量受到土壤硝态氮含量的调控.     

2D NMR of the Metabolic Antioxidant Dihydrolipoic Acid and its Derivatives

Dihydroplipoate and lipoate are physiological thiols which in addition to their coenzyme functions exhibit antioxidant activity. For NMR investigations of their protective mechanism in biological and model systems it is very important to know the full assignment of proton and carbon spectra of these molecules in water (D₂O). An unambiguous assignment of proton and carbon NMR spectra has been made for dihydrolipoate and its short chain derivatives bisnor-and tetranor-lipoic acid in D₂O and CDCl₃ solutions using 2D NMR methods.

Oxidation of dihydrolipoic acid produces substantial electron density deshielding of the carbons nearest to the SH groups with the largest shift found at the inner SH group (17.79 ppm in D₂O, 16.93 in CDCl₃) and almost no changes in the tail portion of the molecule. However, bisnor-dihydrolipoic acid and especially tetranor-dihydrolipoic acid have more carbon deshielding near the outer SH group of the molecule which correlates with their known diminished ion chelating activity.

Moreover, the proton triplet at position 2 of lipoic acid has strong pH dependence (pK = 4.58) due to the close proximity to the carboxylic group and this feature may be used for monitoring pH.     

Copper(II) coordination polymers derived from triethanolamine and pyromellitic acid for bioinspired mild peroxidative oxidation of cyclohexane

The new inorganic 1D coordination polymer [Cu₂(H₃tea)₂(μ₄-pma)]_n has been prepared, via self-assembly in aqueous medium, from copper(II) nitrate, triethanolamine (H₃tea), pyromellitic acid (H₄pma) and lithium hydroxide, and characterized by IR spectroscopy, elemental and single-crystal X-ray diffraction analyses. This compound and the related 2D polymer [Cu₂(μ-H₂tea)₂{μ₃-Na₂(H₂O)₄}(μ₆-pma)]_n · 10nH₂O are shown to mimic the alkane partial oxidation activity of the multicopper particulate methane monooxygenase, acting as catalysts precursors for the peroxidative oxidation of cyclohexane into cyclohexanol and cyclohexanone, by hydrogen peroxide (as green oxidant) and at room temperature in acidic MeCN/H₂O medium. An overall yield (based on cyclohexane) of 29% has been achieved.