城市化对空气污染人群暴露贡献的定量方法研究

短期快速城市化引发一系列生态环境问题,尤其是近年来以细颗粒物(PM_(2.5))为代表的城市与区域空气污染问题。人群的污染暴露一方面是因为污染区范围的扩张,另外一方面则归因于城市化引发的人口迁移,目前的研究重点关注于前者的贡献,而忽略了后者的贡献。因此,建立了城市化对空气污染人群暴露贡献的定量方法,并选取我国PM_(2.5)污染最为严重的京津冀城市群开展了实证研究,通过利用2000、2005、2010、2015年PM_(2.5)浓度和人口栅格数据以及人口自然增长率数据,定量评估了城市化引发的人口迁移对空气污染人群暴露的贡献。研究结果显示:(1)京津冀地区受污染影响面积和人口变化显著,造成大量的人口暴露于PM_(2.5)污染。(2)城市化引发的人口迁移与自然增长贡献率方面:总体上,2000—2015年,京津冀城市群总的人口迁移贡献率为48%,北京市和天津市总的人口迁移贡献率分别为94%和88%,而河北省污染总的人口迁移贡献率为-32%。其中在污染保持区,北京市和天津市的人口迁移贡献率均接近100%,而河北省的迁移贡献率为-26%,尤其在2010—2015年,河北省衡水市的人口迁移贡献率达到-6613%;在污染新增区,北京市和天津市的人口迁移贡献率分别为86%和84%,而河北省污染的人口迁移贡献率为-757%。本研究建立了定量化的方法揭示了城市化在空气污染人群暴露中的定量贡献,为科学引导城市化发展提供了定量的手段,为合理规划京津冀城市群地区的人口流动与空气污染奠定了数据基础。     

冬季PM2.5的气象影响因素解析

气象因素能够显著影响PM_(2.5)浓度,可减轻或加剧城市空气污染,尤其是在雾霾严重的冬季。同时由于城市间污染物排放强度和扩散条件的差异,雾霾的发生往往具有较强的区域性。选择了石家庄、西安、北京、太原、广州5个不同污染区域的典型城市,首先分析多个气象因子与PM_(2.5)浓度的关系,进而研究气象因素对PM_(2.5)浓度变异解释度的差异,以及气象因子对PM_(2.5)浓度影响的相对重要性,进一步对比分析气象因素对PM_(2.5)浓度影响在不同污染程度的城市之间的差异,解析了不同城市的主要气象影响因素和气象因素的综合影响程度。研究结果表明:(1)气象条件与PM_(2.5)日浓度显著相关,且在不同污染程度的城市与PM_(2.5)浓度相关的气象因子不同。与石家庄冬季PM_(2.5)浓度相关的气象因素为相对湿度、平均风速;与西安PM_(2.5)浓度相关的主要气象因素为相对湿度、平均风速和最大持续风速;与北京PM_(2.5)浓度相关的主要气象因素相对湿度、日均温度、平均风速、最大持续风速和最低温;与太原PM_(2.5)浓度相关的主要气象因素为日均温、相对湿度、平均风速、最高温、最低温和最大持续风速;与广州PM_(2.5)浓度相关的主要气象因素为相对湿度、平均风速、最高温和降雨量。(2)PM_(2.5)浓度越高的地区,气象因素能够解释的PM_(2.5)浓度变异越小。严重污染区的石家庄气象因素多元回归分析的R~2为0.27,重污染区的西安气象因素多元回归分析R~2为0.29,中污染区的北京气象因素多元回归分析R~2为0.46,污染地区的太原气象因素多元回归分析R~2为0.67。研究结果揭示了不同城市的主要气象影响因素及其综合影响程度,可为城市PM_(2.5)控制和预测精度提高提供理论参考,并为区域生态环境规划和城市协调发展提供科学依据。     

城市群空气污染综合评估范式与应用——以京津冀城市群PM2.5污染为例

城市群已成为中国城市发展的主要形式，城市化发展引发的一系列环境污染问题成为目前的研究重点之一，尤其是近年来明显的空气污染问题。由于传统的针对某一城市地区进行细致研究，难以解决在城市聚集的城市群下形成的区域性空气污染来源和影响机制等问题，使区域性空气污染造成的负面效应难以评估。通过构建综合评估模型范式，并运用空间分析，对京津冀168个区县2000年，2005年，2010年，2015年PM_2.5人口暴露风险、人类活动对PM_2.5的贡献、以及5种土地利用类型的"源汇"特征进行了实证研究。结果发现：（1）2000-2015年，京津冀城市群的人口暴露风险、空气污染分布、综合评估结果总体呈现北低南高的现象。（2）2000-2015年，各县域的人口暴露风险和空气污染的程度、范围呈上升趋势。不同的土地利用类型具有不同的源汇特征，且对污染的贡献不同。本研究通过综合评估模型范式对城市群或区域城市发展与空气质量的权衡关系模式开展量化解析，为城市的可持续发展提供了科学的范式和初步的实证示范。     

城市规模对大气污染物NO2和PM2.5浓度的影响

随着我国城市的快速发展,城市的区域性大气污染问题日益突出,尤其是大城市和超大城市的污染问题更加严重。那么城市规模的扩大是否必然导致空气污染的加剧?控制城市人口规模是否是防治空气污染的有效手段?这些问题成为空气污染防治中政府、公众和学者广泛关注的焦点。采用2013年冬季全国114个重点城市两种典型大气污染物-NO_2(传统)和PM_(2.5)(新型)-浓度的实时监测数据,首先分析了这两种大气污染物的空间分布特征,进而定量分析城市人口规模和大气污染物浓度的关系。结果显示:(1)仅有21%的城市NO_2浓度达到WHO的城市年均浓度标准(40μg/m~3),全部城市的PM_(2.5)浓度高于WHO年均浓度标准(10μg/m~3);(2)大气污染物的空间分布具有显著的集聚特征和区域性特征,表现为:NO_2呈较为分散的空间分布,而PM_(2.5)的空间分布呈现"北高南低、内陆高沿海低"的特征。NO_2浓度高的区域主要分布在天津、河北东南部和山东中部地区,PM_(2.5)浓度高的区域主要分布于河北西南部和山东西部;(3)常住人口规模同冬季NO_2和PM_(2.5)浓度呈倒"U"型关系;在1000到1200万的城市冬季平均NO_2和PM_(2.5)浓度最高(NO_2:69.28μg/m~3,PM_(2.5):119.58μg/m~3)。(4)总人口低于1200万的城市,冬季NO_2浓度和PM_(2.5)浓度随着城市规模增加而显著升高(NO_2:r=0.44,P0.01;PM_(2.5):r=0.43,P0.01);总人口高于1200万的城市,NO_2浓度同城市规模呈显著负相关关系(r=0.91,P0.05),PM_(2.5)浓度随城市规模增加逐渐降低。(5)常住人口密度在1000人/km~2以下的重点城市,NO_2和PM_(2.5)浓度同城市人口密度呈显著正相关关系(NO_2:r=0.23,P0.05;PM_(2.5):r=0.36,P0.01)。常住人口密度在1000人/km~2以上的城市人口密度同NO_2和PM_(2.5)浓度呈显著负相关关系(NO_2:r=-0.61,P0.05;PM_(2.5):r=0.63,P0.01)。以上研究结果可以为划定不同大气污染物的重点防治区域和制定联合防治行动计划提供理论依据,并为重点城市大气污染治理和城市人口规模控制理论完善提供参考。     

基于城市绿地滞尘模型的上海市绿色空间滞留PM2.5功能评估

绿色空间对大气颗粒物有一定吸收滞留作用,是改善空气环境质量与维护城市生态安全的重要区域。该文基于高分2号卫星影像识别2017年上海市绿色空间,并利用城市绿地滞尘模型,结合上海市降水、风速等气象数据与空气质量监测数据,评估了绿色空间滞留PM_(2.5)功能及其差异。结果表明:2017年上海市绿色空间面积3354 km~2,可滞留PM_(2.5) 3533 t,约合单位面积滞留PM_(2.5) 10.5 kg hm~(-2) a~(-1)。从绿色空间类型来看,林地滞留PM_(2.5)能力最强,可达20.2 kg hm~(-2) a~(-1),远高于草地9.1 kg hm~(-2) a~(-1)和农田8.7 kg hm~(-2) a~(-1)的滞留能力。从季节差异来看,绿色空间夏季滞留PM_(2.5)能力最高,然后依次为秋季、春季和冬季。从植被分布格局来看,林草地和农田吸滞PM_(2.5)的能力随植被盖度的增加而提高。在区域差异上,崇明区绿色空间滞留PM_(2.5)能力最高,其余地区呈现出中心城区低、周边高的趋势。为此建议上海市重点优化中心城区的绿色空间格局,增植立体绿化与高滞尘能力树种。     

北京城市森林不同天气状况下PM2.5浓度变化

基于北京市环境保护监测中心植物园空旷地和市区非植被区的PM_(2.5)实时监测数据,结合植物园林内PM_(2.5)监测站数据,分析了2013年3月—2014年2月不同天气状况下的PM2.5质量浓度变化。结果表明:1降雨天气和大风天气下PM_(2.5)质量浓度变化无滞后性,雨前和雨中变动较大,雨后变化较小,雨后1天PM_(2.5)质量浓度降低到最低值((14.88±7.34)μg/m~3,下降了(89.36±4.78)%),雪后第2天达到最低值((13.76±6.73)μg/m~3,下降了(88.53±5.59)%);2大风天气下PM_(2.5)质量浓度波动较小,在东北风和西南风影响下PM_(2.5)质量浓度值较高(80.61μg/m~3),在东南风影响下PM_(2.5)浓度值较低(54.22μg/m~3);3高温高湿天气下PM_(2.5)质量浓度市区非植被区滞后1—2h到达峰值,植物园林内监测站和植物园空旷地高峰无滞后性,植物园林内监测站变动剧烈、消减作用强,市区非植被区和植物园空旷地较为平缓;4不同天气下PM_(2.5)质量浓度均表现为市区非植被区植物园林内植物园空旷地;5城市森林具有强大的净化大气污染物和吸滞PM_(2.5)等颗粒物的功能,森林环境的空气质量优于非植被区,森林空旷地的空气质量优于森林内部。     

不同污染程度下毛白杨叶表面PM2.5颗粒的数量及性质和叶片气孔形态的比较研究

选择了北京市环境PM_(2.5)浓度不同的两个采样点的毛白杨(Populus tomentosa Carr.)作为研究对象,利用环境扫描电镜及X-射线能谱仪对杨树叶片表面滞留的PM_(2.5)颗粒进行了观察、统计和成分分析,并研究了叶片气孔对环境颗粒物污染的适应性变化。结果表明:夏秋两季西直门叶片样品上下表面的PM_(2.5)数量均多于森林公园样品这说明环境PM_(2.5)浓度是影响叶片表面滞留颗粒物数量的主要原因;其中叶片上表面是滞留PM_(2.5)颗粒的主要区域。森林公园样品中PM_(2.5)颗粒性质比较单一,硅铝酸盐颗粒和石英颗粒占很大比例,二者的主要来源均为天然源,如土壤扬尘、矿物颗粒等;而西直门采样点叶片样品滞留的PM_(2.5)颗粒的元素组成更为复杂,其中50%以上的硅铝酸盐颗粒检测出了明显的铜、钾、氯、钠等元素的谱峰其来源主要是工业排放;西直门样品PM_(2.5)的含硫量高于森林公园样品,且夏季明显高于秋季。研究还发现有少数PM_(2.5)颗粒进入了毛白杨叶片的气孔而且不同污染程度下气孔的形态特征存在差异。与森林公园毛白杨叶片的气孔相比,西直门处的毛白杨叶片气孔的长度、宽度、面积和气孔密度均较小,说明较高的PM_(2.5)污染程度对毛白杨叶片的形态发育有一定影响。研究结果可以为揭示植物叶片阻滞、吸收大气颗粒污染物的机制、合理选择和优化城市绿化树种从而改善空气质量提供一定的科学理论依据。     

基于实地监测的城市林木调控PM2.5能力研究

随着城市的不断扩张,PM_(2.5)污染凸显,引起广泛关注。研究表明,城市林木为城市环境提供了重要的生态保障,在调控、缓解、降低城市PM_(2.5)污染危害等方面发挥极其重要的作用,通过筛选树种、优化配置结构、提高林木质量等方面进行城市林木前瞻性布局。然而,结合前期研究基础如何进一步深入研究并研究突破城市林木调控PM_(2.5)污染机制与机理,实现调控PM_(2.5)效应的最大化、最优化,依然是一个亟待解决的难题,这迫切需要在多尺度、多维度进行调控PM_(2.5)效应研究,并在不同尺度、不同维度进一步进行结合、延伸。对基于实地监测的城市林木调控PM_(2.5)能力研究现状相关文献进行归纳总结,并从林木单位叶面积与形态特征、配置结构特征、气象条件以及其他因素等方面归纳城市林木调控PM_(2.5)机制,同时从城市林木调控PM_(2.5)效应的时间变化特征、水平距离和垂直变化特征、内外变化特征等方面总结城市林木调控PM_(2.5)时空特征。最终提出研究城市林木调控PM_(2.5)效应目前存在的主要问题以及未来研究展望。     

大气颗粒物(PM2.5、PM10)对地表景观结构的响应研究进展

颗粒物PM_(2.5)、PM_(10)是近年来我国大气首要污染物,威胁环境和人类健康。地表景观结构直接或间接影响PM_(2.5)、PM_(10)浓度,了解其影响过程和机理对于改善生态环境具有重要意义。系统总结了国内外关于PM_(2.5)、PM_(10)对地表景观结构响应的研究成果,指出研究中出现不确定性的可能影响因素,并对今后的发展方向进行展望。得出基本结论:(1)地表景观类型的构成及其格局显著影响大气颗粒物浓度,对PM_(2.5)、PM_(10)起到"源"和"汇"的作用。(2)地表景观结构引起局地气候变化并影响颗粒物的迁移转化,但其影响过程和机理复杂,研究结论并不明确。(3)颗粒物浓度和地表景观数据主要通过实际监测或遥感处理方法获得,但因为获取方法、监测点微观环境及遥感影像等因素影响,导致数据具有不确定性,加上时空尺度相对应的复杂性,大大限制了地表景观结构与PM_(2.5)、PM_(10)响应关系的研究进展,是未来要突破的难点。(4)PM_(2.5)、PM_(10)对地表景观结构响应的区域时空差异及过程,局地小气候变化对颗粒物浓度的影响过程和强度,主要景观类型尤其是水体、湿地景观对大气颗粒物浓度的影响过程、机理与贡献程度等是未来需要关注的方向。     

北京西山不同海拔油松林PM2.5浓度及叶片吸附量变化规律

以北京西山不同海拔梯度油松人工林为研究对象,对油松林PM_(2.5)浓度变化和叶片PM_(2.5)吸附量进行分析,并应用电子显微镜对不同海拔油松叶表面微形态特征进行观察,阐释叶片吸附PM_(2.5)差异。结果表明:随着海拔升高PM_(2.5)质量浓度逐渐降低,不同海拔油松林PM_(2.5)质量浓度日变化均呈典型的双峰曲线,7:00和19:00是一天的两个峰值,最小值出现在13:00—15:00左右;从不同月份看,不同海拔油松林PM_(2.5)质量浓度最高值出现在冬季的2月,最低值在8月;不同海拔油松林PM_(2.5)质量浓度全年均值为84 m((102.28±18.44)μg/m~3)110 m((94.18±18.34)μg/m~3)160 m((81.53±19.23)μg/m~3)230 m((75.39±15.71)μg/m~3);随着海拔升高单位叶面积PM_(2.5)吸附量逐渐减小,每升高50 m,单位叶面积PM_(2.5)吸附量降低23.25%,每公顷PM_(2.5)吸附量下降26.43%,不同海拔油松林每公顷PM_(2.5)吸附量全年均值为84 m((8.61±1.08)kg/hm~2)110 m((7.30±0.94)kg/hm~2)160 m((6.35±0.99)kg/hm~2)230 m((4.34±1.14)kg/hm~2);处于低海拔的油松叶表面较粗糙,气孔内部和周围聚集大量颗粒物,在叶面形态上更有利于吸附PM_(2.5),高海拔则相反。高海拔空气质量优于低海拔,低海拔的植物吸附颗粒物多于高海拔。研究结果可为城市造林和森林净化大气提供数据支持。     

Unambiguous through-bond sugar-to-base correlations for purines in 13C, 15N-labeled nucleic acids: The HsCsNb,HsCs(N)bCb,and HbNbCb experiments

Summary A set of three 3D (¹H, ¹³C, ¹⁵N) triple-resonance correlation experiments has been designed to provide H1-H8 intraresidue sugar-to-base correlations in purines in an unambiguous and efficient manner. Together, the H_sC_sN_b, H_sC_s(N)_bC_b, and H_bN_bC_b experiments correlate the H1 sugar proton to the H8 proton of the attached base by means of the {H1, C1, N9, C8, H8} heteronuclear scalar coupling network. The assignment strategy presented here allows for unambiguous H1-H8 intraresidue correlations, provided that no two purines have both the same H1 and C1 chemical shifts and the same C8 and N9 chemical shifts. These experiments have yielded H1-H8 intraresidue sugar-to-base correlations for all five guanosines in the [¹³C, ¹⁵N] isotopically labeled RNA duplex r(GGCGCUUGCGUC)₂.     

Aromatic C20F20 cage and its endohedral complexes X@C20F20 (X = H-, F-, Cl-, Br-, H, He)

The structure and stability of endohedral X@C₂₀F₂₀ complexes (X = H⁻, F⁻, Cl⁻, Br⁻, H, He) have been computed at the B3LYP level of theory. All complexes in I _h symmetry were found to be energy minimum structures. H⁻@C₂₀F₂₀ and F⁻@C₂₀F₂₀ complexes have negative inclusion energies, while other complexes have positive inclusion energies. Similarity between C₂₀F₂₀ and C₂₀H₂₀ has been found for X = H and He. On the basis of the computed nucleus independent chemical shift values at the cage center, both C₂₀F₂₀ and C₂₀F₂₀ are aromatic. Figure Endohedral X@C₂₀F₂₀ complexes     

Di(1,N-ethenoadenosine)5′, 5-P,P-tetraphosphate, a fluorescent enzymatically active derivative of Ap4A

Di(1,N⁶-ethenoadenosine) 5′, 5-P¹, P⁴-tetraphosphate, ε-(Ap₄A), a fluorescent analog of Ap₄A has been synthesized by reaction of 2-chloroacetaldehyde with Ap₄A. At neutral pH this Ap₄A analog presents characteristic maxima at 265 and 274 nm, shoulders at ca 260 and 310 nm and moderate fluorescence (λ_exc 307 nm, λ_em 410 nm). Enzymatic hydrolysis of the phosphate backbone produced a slight hyperchromic effect but a notorious increase of the fluorescence emission. Cytosolic extracts from adrenochromaffin tissue as well as cultured chromaffin cells were able to split ε(Ap₄A) and catabolize the resulting ε-nucleotide moieties up to ε-Ado.     

Synthesis, biological activity and molecular modelling studies of tricyclic alkylimidazo-, pyrimido- and diazepinopurinediones

Syntheses and biological activities of imidazo-, pyrimido- and diazepino[2,1-f]purinediones containing N-alkyl substituents (with straight, branched or unsaturated chains) are described. Tricyclic derivatives were synthesized by the cyclization of 8-bromo-substituted 7-(2-bromoethyl)-, 7-(3-chloropropyl)- or 7-(4-bromobutyl)-theophylline with primary amines under various conditions. Compound 22 with an ethenyl substituent was synthesized by dehydrohalogenation of 9-(2-bromoethyl)-1,3-dimethyltetrahydropyrimido[2,1-f]purinedione. The obtained derivatives (5–35) were initially evaluated for their affinity at rat A₁ and A_2A adenosine receptors (AR), showing moderate affinity for both adenosine receptor subtypes. The best ligands were diazepinopurinedione 28 (K_i = 0.28 μM) with fivefold A_2A selectivity and the non-selective A₁/A_2A AR ligand pyrimidopurinedione 35 (K_i A₁ = 0.28 μM and K_i A_2A = 0.30 μM). The compounds were also evaluated for their affinity at human A₁, A_2A, A_2B and A₃ ARs. All of the obtained compounds were docked to the A_2A AR X-ray structure in complex with the xanthine-based, potent adenosine receptor antagonist—XAC. The likely interactions of imidazo-, pyrimido- and diazepino[2,1-f]purinediones with the residues forming the A_2A binding pocket were discussed. Furthermore, the new compounds were tested in vivo as anticonvulsants in maximal electroshock, subcutaneous pentylenetetrazole (ScMet) and TOX tests in mice (i.p.). Pyrimidopurinediones showed anticonvulsant activity mainly in the ScMet test. The best derivative was compound 11, showing 100 % protection at a dose of 100 mg/kg without symptoms of neurotoxicity. Compounds 6, 7, 8 and 14 with short substituents showed neurotoxicity and caused death. In rat tests (p.o.), 9 was characterized by a high protection index (>13.3). AR affinity did not apparently correlate with the antiepileptic potency of the compounds.

Electronic supplementary material

The online version of this article (doi:10.1007/s11302-013-9358-3) contains supplementary material, which is available to authorized users.     

Early years of oxygenase research in Bethesda, Osaka, Urbana, and Kanazawa

In this brief review, I recollect my experiences of how the studies of pyrocatechase and salicylate hydroxylase led to the isolation and revelation of P450cam. Those experiences were instrumental in the separation, purification, and characterization of the two forms of adrenal cortex mitochondrial P450.     

H2SO4-silica-promoted 'on-column' removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups

H₂SO₄-silica-promoted removal of benzylidene, isopropylidene, trityl and tert-butyldimethylsilyl groups from sugar derivatives was accomplished by following an ‘on-column’ protocol in a virtually waste-free condition.     

Photosynthesis pathways,ecological characteristics,and the geographical distribution of the Cyperaceae in Japan

Summary The nature of the photosynthetic pathways of Cyperaceae found in Japan were investigated on the basis of Kranz anatomy, the CO₂ compensation concentration and previously reported data. Among 301 species (96% of all cyperaceous species recorded in the region), 58 species were classified as being C₄ plants. These C₄ species were scattered among the tribes Fimbristylideae, Lipocarpheae, Cypereae and Rhynchosporeae in the subfamily Cyperoideae. The genera Cyperus, Eleocharis and Rhynchospora included, in Japan, both C₃ and C₄ species within a single genus. Using these data, an analysis was made of the ecological characteristics and geographical distribution of the C₃ and C₄ species in Japan. Although cyperaceous species grow in markedly different environments, the majority were found in wet and aquatic areas (61%) or shaded areas, such as forest floors (20%). Most of the C₃ species were also hygrophytes (58%) and forest-living species (25%), and C₃ species growing in mesic and dry areas were relatively rare. The C₄ species inhabited wet and aquatic (75%), mesic (13%) and dry areas (6%) and showed marked ecological characteristics with respect to soil-moisture conditions, unlike other C₄ plants, although they were absent from shaded habitats. In order to determine the climatic factors that influence the relative floristic abundance of C₃ and C₄ members of the Cyperaceae in Japan, the ratios of number of C₄ species to the total number of members of Cyperaceae (C₄ percentage) in 16 representative locales were examined in terms of various climatic variables. There were strong positive correlations between the C₄ percentage and temperature. Among the C₃ groups of three subfamilies, there were different distributional trends for various temperature regimes. The C₃ subfamily Caricoideae increased its relative contribution to the cyperaceous flora with a decrease in mean annual temperature, while the C₃ subfamily Sclerioideae exhibited the opposite pattern. The C₃ group of the subfamily Cyperoideae did not show any marked change in pattern along temperature gradients, unlike the two other C₃ subfamilies, and seemed to be heterogeneous in terms of its response to temperature. The relationships between the C₄ biochemical subtypes and ecological characteristics are also discussed.     

Photosynthetic Pathways,Life Forms,and Reproductive Types for Forage Species Along the Desertification Gradient on Hunshandake Desert,North China

Floristic compositions, life forms, reproductive types for forage species, and their responses to desertification in Hunshandake desert were studied. 164 species, in 30 families and 94 genera, were identified with C₃ (137 species), C₄ (25 species), and CAM (2 species) photosynthesis. Of the 25 C₄ species, 76 % were grasses and Chenopodiaceae species (hereafter chenopods). This suggests that the C₄ species mainly occurred in a few families in the desert region. The reduction of C₃ species and the increase of C₄ species with desertification indicated that C₄ species might have higher tolerance to environmental stresses (e.g. dry and poor soil). Relatively more hemicrytophyte and therophyte forms in the desert are related to the local temperate climate and vegetation dynamics. Relatively greater proportions of C₄/C₃ and clonal species/sexual species at mobile dune showed that the C₄ species and clonal species could make greater contribution to sand land restoration in the Hunshandake desert.     

Purification,Characterization, and Molecular Cloning of a Pyranose Oxidase from the Fruit Body of the Basidiomycete,Tricholoma matsutake

A new H₂O₂-generating pyranose oxidase was purified as a strong antifungal protein from an arbuscular mycorrhizal fungus, Tricholoma matsutake. The protein showed a molecular mass of 250 kDa in gel filtration, and probably consisted of four identical 62 kDa subunits. The protein contained flavin moiety and it oxidized D-glucose at position C-2. H₂O₂ and D-glucosone produced by the pyranose oxidase reaction showed antifungal activity, suggesting these compounds were the molecular basis of the antifungal property. The V _max, K _m, and k _cat for D-glucose were calculated to be 26.6 U/mg protein, 1.28 mM, and 111/s, respectively. The enzyme was optimally active at pH 7.5 to 8.0 and at 50°C. The preferred substrate was D-glucose, but 1,5-anhydro-D-glucitol, L-sorbose, and D-xylose were also oxidized at a moderate level. The cDNA encodes a protein consisting of 564 amino acids, showing 35.1% identity to Coriolus versicolor pyranose oxidase. The recombinant protein was used for raising the antibody.     

Flurbiprofen,A Cyclooxygenase Inhibitor,Reduces the Brain Arachidonic Acid Signal in Response to the Cholinergic Muscarinic Agonist,Arecoline, in Awake Rats

Cholinergic muscarinic receptors, when stimulated by arecoline, can activate cytosolic phospholipase A₂ (cPLA₂) to release arachidonic acid (AA) from membrane phospholipid. This signal can be imaged in the brain in vivo using quantitative autoradiography following the intravenous injection of radiolabeled AA, as an increment in a regional brain AA incorporation coefficient k*. Arecoline increases k* significantly in brain regions having muscarinic M_1,3,5 receptors in wild-type but not in cyclooxygenase (COX)-2 knockout mice. To further clarify the roles of COX enzymes in the AA signal, in this paper we imaged k* following arecoline (5 mg/kg i.p.) or saline in each of 81 brain regions of unanesthetized rats pretreated 6 h earlier with the non-selective COX inhibitor flurbiprofen (FB, 60 mg/kg s.c.) or with vehicle. Baseline values of k* were unaffected by FB treatment, which however reduced by 80% baseline brain concentrations of prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂), eicosanoids preferentially derived from AA via COX-2 and COX-1, respectively. In vehicle-pretreated rats, arecoline increased the brain PGE₂ but not TXB₂ concentration, as well as values for k* in 77 of the 81 brain regions. FB-pretreatment prevented these arecoline-provoked changes. These results and those reported in COX-2 knockout mice suggest that the AA released in brain following muscarinic receptor-mediated activation is lost via COX-2 to PGE₂ but not via COX-1 to TXB₂, and that increments in k* following arecoline largely represent replacement by unesterified plasma AA of this loss.