Electrochemical reactions of cyanocobalamin in acidic media

Electrochemical reactions of cyanocobalamin, CN-Cbl[Co(III)], were studied at glassy carbon electrodes in acidic media by means of cyclic voltammetry and differential pulse polarography. It was found that in pH 0 solution, CN-Cbl[Co(III)] exists mainly in the base-off form, {CN-Cbl[Co(III)]}(base-off). It can undergo a one-electron reduction and a follow-up chemical reaction to form {H2O-Cbl[Co(II)]}(base-off). The rate-constant k of the follow-up decyanation reaction is 0.022 s(-1). {H2O-Cbl[Co(II)]}(base-off) is further reduced to obtain H2O-Cbl[Co(I)]. (C) 1997 Elsevier Science S.A.

单叶蔓荆子挥发油成分的GC/MS分析

采用气相色谱／质谱（ＧＣ／ＭＳ）联用技术对山东泰山产单叶蔓荆子挥发油的化学成分进行了分析，分离出３０多个峰，确认了其中２８种成分，占总离子流的９５％以上，并对挥发油的主要化学成分Δ３－蒈烯，用气相色谱／傅里叶红外光谱（ＧＣ／ＦＴＩＲ）法进行了验证。

活体心肌缺血再灌自由基产生和清除的ESR研究

ＥＳＲ和自旅捕捉技术用于研究活体动物犬心肌缺血再灌产生的自由基，ＰＢＮ从冠状静脉血液中捕捉到了ＯＨ自由基，直接地证实了缺血再灌细胞膜损伤的活性氧自由基作用机制；实验还看到一种甾体皂甙药物具有保护心肌细胞．防止自由基损伤的功能．

新型导电高分子材料的导电性与其结构的关系

新型导电高分子材料的导电性与其结构的关系梁洪泽，宋永贤，丁黎明，綦玉臣，李丽霞，景遐斌，王佛松（中国科学院长春应用化学研究所，长春，１３００２２）自Ｗｒｉｇｈｔ首次报道了聚环氧乙烷（ＰＥＯ）－碱金属盐（ＭＸ）配合物的离子导电性以来，有关各种聚合物固体...

聚合物载体－稀土金属络合物的研究 ⅩⅢ．聚［苯乙烯－甲基丙烯酸β（甲基亚硫酰基）乙酯］的结构与其稀土金属络合物催化丁二烯聚合的活性

从测得的竞聚率计算了单体链节在聚［苯乙烯－甲基丙烯酸β（甲基亚硫酰基）乙酯］（ＰＳＭ）中的序列分布。苯乙烯（Ｓ）或甲基丙烯酸β（甲基亚硫酰基）乙酯（Ｍ）的长序列的概率随着ＰＳＭ中相应单体含量的增加而增加。对于Ｓ和Ｍ摩尔分数大致相等的ＰＳＭ，单体链节的长序列分布函数值相接近。用与此结构相近的ＰＳＭ合成的稀土金属络合物，其催化活性不佳。在Ｍ短序列分布和Ｓ长序列分布较高的情况下，络合物的催化活性最好。所得聚丁二烯的微观结构与ＰＳＭ中单体单元的分布无关。

STUDY ON MASS-TRANSPORT IN EASTMAN-AQ POLYMER FILM BY USING NON-STEADY-STATE CHRONOAMPEROMETRY AT AN ULTRAMICRODISK ELECTRODE

Non-steady-state chronoamperometry of ultramicroelectrodes is a powerful method for the study of mass transport in polymer films. This method has many advantages over the conventional methods at a macroelectrode and the steady state method at an ultramicroelectrode, which yield the most information. The apparent diffusion coefficient, D(app), and the concentration of reactant in the film, c(f), can be determined from a single experiment without knowing the thickness of the film. We studied the transport of several species such as Ru(NH3)63+, Ru(bpy)3(2+), NR and MV2+ in Eastman-AQ polymer film coated ultramicroelectrodes by using this method.

多晶CdS太阳电池p-n结电容的测量及应用

介绍了p-n结电容测量方法。通过测量C-V特性研究了Cds太阳电池的热处理及上栅过程,分析并讨论了p-n结的变化与电池不稳定的关系。初步研究了扩散电位的测定问题。

用XPS、SIMS对稀土-6063铝合金表面状态的研究

用X射线光电子能谱(XPS)和二次离子质谱仪(SIMS)等表面分析方法对稀土-6063铝合金进行了研究,发现稀土铝合金的表面为金属铝和铝的氧化物两种形态。稀土及镁两者的协同作用,可以缓和铝合金的氧化程度。SIMS结果表明,加入适量稀土,可以抑制镁在稀土-6063铝合金的表面偏析作用。

多相氧载体CoO-MgO的ESR研究

用ESR方法研究了CoO-MgO固溶体作为多相氧载体的可逆吸氧性质。发现CoO-MgO表面的Co~(2+)可以以两种方式与分子氧可逆结合,一种形成Co~(2+)-O_2,它给出了与MgO晶格中Co~(2+)相似的各向同性的信号(g=4.2);一种形成Co~(2+)-O_2~-,它给出轴对称的信号(g_‖=2.141,A_‖=30G,g_⊥_=1.980,A_⊥=15G)。我们认为Co~(2+)-O_2是表面Co_(5c)~(2+)与O_2结合产生的,而Co~(3+)-O_2~-是由表面Co_(4c)~(2+)或Co_(3c)~(2+)与O_2结合形成的。

The structure of Aquifex aeolicus sulfide:quinone oxidoreductase, a basis to understand sulfide detoxification and respiration

Sulfide: quinone oxidoreductase (SQR) is a flavoprotein with homologues in all domains of life except plants. It plays a physiological role both in sulfide detoxification and in energy transduction. We isolated the protein from native membranes of the hyperthermophilic bacterium Aquifex aeolicus, and we determined its X-ray structure in the "as-purified,'' substrate-bound, and inhibitor-bound forms at resolutions of 2.3, 2.0, and 2.9 angstrom, respectively. The structure is composed of 2 Rossmann domains and 1 attachment domain, with an overall monomeric architecture typical of disulfide oxidoreductase flavoproteins. A. aeolicus SQR is a surprisingly trimeric, periplasmic integral monotopic membrane protein that inserts about 12 angstrom into the lipidic bilayer through an amphipathic helix-turn-helix tripodal motif. The quinone is located in a channel that extends from the si side of the FAD to the membrane. The quinone ring is sandwiched between the conserved amino acids Phe-385 and Ile-346, and it is possibly protonated upon reduction via Glu-318 and/or neighboring water molecules. Sulfide polymerization occurs on the re side of FAD, where the invariant Cys-156 and Cys-347 appear to be covalently bound to polysulfur fragments. The structure suggests that FAD is covalently linked to the polypeptide in an unusual way, via a disulfide bridge between the 8-methyl group and Cys-124. The applicability of this disulfide bridge for transferring electrons from sulfide to FAD, 2 mechanisms for sulfide polymerization and channeling of the substrate, S2-, and of the product, S-n, in and out of the active site are discussed.

Sequence analysis of Arthrospira maxima based on fosmid library

Arthrospira (Spirulina) (Setchell& Gardner) is an important cyanobacterium not only in its nutritional potential but in its special biological characteristics. An unbiased fosmid library of Arthrospira maxima FACHB438 that contains 4300 clones was constructed. The size distribution of insert fragments is from 15.5 to 48.9 kb and the average size is 37.6 kb. The recombination frequency is 100%. Therefore the library is 29.9 equivalents to the Arthrospira genome size of 5.4 Mb. A total of 719 sample clones were randomly chosen from the library and 602 available sequences, which consisted of 307,547 bases, covering 5.70% of the whole genome. The codon usage of A. maxima was not strongly biased. GC content at the first position of codons (46.9%) was higher than the second (39.8%) and the third (45.5%) positions. GC content of the genome was 43.6%. Of these sequences, 287 (47.7%) showed high similarities to known genes, 63 (10.5%) to hypothetical genes and the remaining 252 (41.8%) had no significant similarities. The assigned genes were classified into 22 categories with respect to different biological roles. Remarkably, the high presence of 25 sequences (4.2%) encoding reverse transcriptase indicates the RT gene may have multiple copies in the A. maxima genome and might play an important role in the evolutionary history and metabolic regulation. In addition, the sequences encoding the ATP-binding cassette transport system and the two-component signal transduction system were the second and third most frequent genes, respectively. These genomic features provide some clues as to the mechanisms by which this organism adapts to the high concentration of bicarbonate and to the high pH environment.

牙鲆生长相关性状遗传力估计

遗传力是数量遗传学的重要参数，对鱼类良种选育具有重要意义。可靠的遗传力估计值可以为合理制定育种计划提供宝贵信息，同时可以预测选择反应。本文按照10×3因子设计方法，10尾雄鱼与3尾雌鱼两两授精，产生10个父系半同胞、3个母系半同胞及30个全同胞家系，以微卫星分子标记为家系鉴定手段，对40日龄牙鲆生长相关性状遗传力进行了估计；同时，初步探讨了因子交配设计及人工控制条件下，亲本对子代遗传贡献率差异及有效群体大小。主要结论包括：1.初步筛选的14个微卫星位点中，有9个（Po91、Po1、Po56、Po20、Poli23、Po89、Poli121、Po42、Po13）在亲本中呈现中、高度多态性：平均等位基因9.4个；平均亲本特异性等位基因4个。用5个位点（Po91、Po1、Po56、Po20、Poli23）为346个子代中的227个个体找到所属家系；继续用另外4个位点（Po89、Poli121、Po42、Po13）分型，成功鉴定72个个体。鉴定率约86%，其中，亲本特异性等位基因的存在使鉴定效率大大提高。以上9个位点可为该群体良种选育工作提供技术支持。2. 发生降解的DNA与完整的DNA，在相同引物、相同PCR体系、相同模板浓度下扩增的带型一致。该结果证实了微卫星分型对降解的DNA同样稳定。3. 亲本对子代的遗传贡献率存在差异。雄亲的贡献率为5.8—14.3%，除3号、9号子代数较少，5号、6号子代数较多外，其它父本基本一致；母本对子代的贡献率差异较大（18.5%—50.6%），这与人工授精前雌亲发育状况、卵子质量检测结果基本一致，在一定程度上说明，母本尤其是卵子质量对鱼类早期存活具有较大影响。4. 家系内子代数目的不平衡导致实际有效群体大小下降。Ne=7.44，比理论有效群体大小（9.23）下降约19%。但与自然交配相比（有效群体下降可达75%），人工控制下的交配在一定程度上可有效限制遗传多样性的下降。5. 基于父本方差组分，40日龄生长相关性状遗传力估计值（h2s±S.E.）为（0.157±0.052）－（0.440±0.137）。加性遗传方差在表型方差中所占的比例，在一定程度上表明该牙鲆群体生长性状具有一定的选择力度。

长江口水域富营养化的形成、演变与特点研究

本文以我国长江口水域富营养化为研究对象，对长江水体溶解态无机氮、磷分布特点和通量变化进行了分析，基于长江流域氮“输入-输出”关系模型探索了水体氮的来源；分析了长江口水域富营养化长期演变及特点；探索了长江口海域低氧区的发生机制。结果如下： 长江水体中NO3--N、NH4+-N、DIN和DIP浓度从上游往下游呈增加趋势，但存在季节差异。长江流域从上游往下游的DIN输送通量的变化主要受水流量的影响，但从上游往下游单位面积年产N量逐渐升高；DIP输送通量从上游往下游呈增加趋势，同时也主要受水流量控制，但从季节变化来讲，DIP的月输送通量受其浓度的控制更加明显。自20世纪60年代来，长江水体中NO3--N、NO2--N、DIN和DIP浓度都处于缓慢上升趋势，但到80年代上升速度明显加快；不同历史时期DIN和DIP的季节变化特点也不尽相同，反映出其来源的差异。同时，本研究采用长江流域氮“输入-输出”关系模型（污染负荷统计模型）对长江水体氮来源进行了分析，估算了各种氮源对水体氮的贡献率。结果表明，2006年向长江流域输入氮的总量为17.6 Tg，其中20%的输入氮转移到了水体（3.5 Tg）。本年度长江大通水文站实测氮输送通量为1.8 Tg，表明约50%的氮在水体输送过程中发生了生物、化学、物理损耗。对于长江水体氮的来源来讲，饲养牲畜粪便氮流失和大气干/湿沉降氮的贡献率较大，分别为26%和25%；农业氮肥流失和城市生活污水排放的贡献率相同，都为17%；农村人口粪便氮流失和工业废水排放的贡献率分别为6%和9%。 自20世纪60年代以来，长江口口门内和外海（盐度>30psu）水体中营养盐浓度增加显著。在表层水体盐度大于22psu海域DIN: PO43--P值表现出了明显升高的历史变化趋势。SiO3: PO43--P值从1959年到1985-86年显著下降，然后到2003-06年有所上升。根据SiO3: PO43--P值和DIN: PO43--P值的长期变化趋势，可以推出，SiO3: DIN值从20世纪50-60年代以后呈现下降趋势。在长江口海域，随着营养盐浓度的增加，浮游生物量的大幅度升高在本研究中得到证实。同时，长江口水域浮游植物种群结构对营养盐结构的长期变化产生响应，研究结果表明，硅藻种类比重从1985-86年84.6% 下降到2004-05年69.8%；年均硅藻丰度占浮游植物总丰度比重在1985-86年达到99.5%，但到2004-05年降低为75.5%，而甲藻丰度比重则由0.7%增大到25.4%。 底层水体DO浓度与Delta S（底层水体与表层水体的盐度之差）和Delta T（表层水体与底层水体的温度之差）成显著负相关，这表明了水体层化或者垂直水体交换是控制长江口水域底层水体溶解氧变化的主要因素，但水体温度层化要比盐度层化在控制低氧区形成上起到更大的作用。上升流在该海域低氧的形成和分布上起到很重要的作用，显著影响低氧水团的垂直分布，也显著影响到溶解氧的水平分布。现场生产的浮游植物可能是低氧区的形成的生物基础，日益增加的叶绿素a浓度和大规模的有害藻华可能是长江口低氧区逐渐增大的原因。本研究认为，此海域低氧区的形成主要受长江冲淡水、台湾暖流的入侵、地形、尤其是温跃层的形成和现场生产的有机物质控制。