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The composition and distribution of metal clusters in the MoFe protein from a nifZ deletion strain (DJ 194) of Azotobacter vinelandii
Huina Zhou,Chunxi Zhang,Ying Zhao,Shaomin Bian,Fei Ren,Huangping Wang,Jufu Huang
Chinese Science Bulletin , 2005, DOI: 10.1360/982005-417
Abstract: Through the anaerobic chromatography on the columns of DEAE 52, Q-Sepharose and Sephacryl S-200, a nitrogenase MoFe protein (ΔnifZ Av1) was obtained from a nifZ deleted mutant of Azotobacter vinelandii (stain DJ194). The results of Western blotting after anoxic native electrophoresis and SDS-PAGE showed that ΔnifZ Av1 was similar to wild type MoFe protein (OP Av1) at the electrophoretic mobility, molecular weight and subunit composition. Furthermore, ΔnifZ Av1 was also similar to OP Av1 at the molybdenum content, EPR signal (g ≈ 4.3, 3.65 and 2.01), and the molar extinction coefficient (Δε) of circular dichroism (CD) at 660 nm region. All of these indicated that, besides having the same α2β2 composition as OP Av1, the ΔnifZ Av1 also contained equal amount of reductive FeMoco in the spin state of S=3/2 to OP Av1. However, the iron content and substrate (C2H2, H+ and N2)-reduction activity of ΔnifZ Av1 were 74% and 46%–50% of those of OP Av1, respectively. Furthermore, the Δε at around 450 nm, which reflects P-cluster in Av1, was obviously lower than that of OP Av1. It suggested that the difference between ΔnifZ Av1 and OP Av1 resulted from P-cluster rather than FeMoco, and from the half number of P-cluster in ΔnifZ Av1, but the composition or redox state of P-cluster in ΔnifZ Av1 were not changed. Thus it could propose that ΔnifZ Av1 is composed of two different αβ subunit pairs. One is a FeMoco- and P-cluster-containing pair, and the other is a P-cluster-deficient but FeMoco-containing pair. Since the deletion of nifZ gene leads to the deficiency of only one of two P-clusters in a α2β2 tetramer, the assembly of P-cluster may not simply depend on one gene product, and so a possible mechanism of NifZ is supposed here.
青海湖棕头鸥(larusbrunnicephalus)夏秋季活动区研究  [PDF]
生态学报 , 2008,
Abstract: 2006年4~9月,采用无线电遥测技术对青海湖重要繁殖水鸟棕头鸥(larus?brunnicephalus)在不同繁殖阶段的活动性,以及与人和鸟的关系进行了研究。对6只棕头鸥个体的遥测结果表明,繁殖初期棕头鸥的活动区较大,进入繁殖中期,活动区明显变小;随后繁殖后期的活动区面积有所增加,到了迁徙前期,活动区面积已接近繁殖初期。不同阶段活动区核心面积(50%fixed?kernel)与活动区变化趋势基本一致。繁殖初期、中期、后期和迁徙前期活动区面积分别为(15.48?km2±4.54?km2)、(1.61?km2±0.41?km2)、(3.53?km2±2.63?km2)和(11.61?km2±9.36?km2)。棕头鸥在不同繁殖阶段的日活动区大小有显著差异。繁殖初期,棕头鸥经常活动于鸬鹚岛、蛋岛和布哈河口,它们都是棕头鸥较好的取食地,鸬鹚岛和蛋岛由于有许多游客投喂食物;在繁殖中期,棕头鸥进入孵化阶段,活动区较繁殖前期明显缩小。由于湟鱼返回布哈河口一带产卵繁殖,棕头鸥经常聚集在此地取食;在繁殖后期,棕头鸥需要寻找大量的食物进行育雏,因此活动范围再度扩大;进入迁徙前期,幼鸟已经长大并学会飞翔,其活动区进一步扩大,与繁殖初期较为接近。
立春时节话竖蛋  [PDF]
刘延柱
力学与实践 , 2013, DOI: 10.6052/1000-0992-20130125
Abstract: 从立春竖蛋的习俗谈起,叙述哥伦布竖蛋,特斯拉利用电磁感应的哥伦布蛋,以及用手捻鸡蛋直立旋转等现象.解释竖蛋现象的力学原理.
陈棕炭炮制一法简介  [PDF]
王月明
中国中药杂志 , 1987,
Abstract: <正>陈棕炭是一味常用中药,具有收敛止血的功效,临床用于吐血、衄血、血淋、尿血、便血下痢等血症。著名中成药十灰丸(散)内含此药。药用陈棕炭的原料一般收集旧棕床拆下之陈棕垫经洗漂干净晒干备用。目前炮制陈棕
蛋鸭的产蛋机制及其营养调控  [PDF]
动物营养学报 , 2010, DOI: 10.3969/j.issn.1006-267x.2010.05.004
Abstract: 目前国内外关于蛋鸭产蛋机制、蛋鸭营养调控方面的研究均落后于养鸭生产的需要,相关的文献报道也比较少。本文将对国内外相关文献报道进行汇总,结合蛋鸡等产蛋机制方面的研究报道,重点综述蛋鸭的产蛋机制研究现状及营养调控措施。
电子测压蛋  [PDF]
祖静,张文栋
兵工学报 , 1991,
Abstract: ?本文介绍了一种新型火炮膛压测试装置——电子测压蛋的工作原理和结构设计特点,给出了电子测压蛋在实弹测试中所获得的数据及压力曲线,并将其与铜柱测压器所测得结果进行了分析对比。
蛋奶发酵食品  [PDF]
郭凤茹
食品科学 , 1987,
Abstract: ?蛋奶发酵食品是一种新型食品,与现在的酸奶酪相似。这种食品风味怡人,特点突出,外观漂亮,并且含有高蛋白。此外还有一些特点和优点。其生产主要过程如下;
中?之??蛋化石  [PDF]
地质论评 , 1937,
Abstract: (一)?去研究中?北方各地新生代後期各地?中,常有易?的一?化石,就是鸵?蛋。他的骨格?也有??,但至今所知尚少。?其蛋皮,差不多每次旅行,都可以?得若干,但完全的究?少?。安特生在他的中?北部之新生界一?中,有一篇文章,??????
宜宾糟蛋  [PDF]
高元庆
食品科学 , 1982,
Abstract: ?宜宾糟蛋是四川省宜宾地区传统土特产品之一,是用粉糟(米酒)泡制而成。蛋质软嫩,气味芳香,味鲜美而微甜,入口有酒香,深受群众欢迎,在港澳和东南亚市场上享有一定盛誉,也是宴会席上别具一格的风味食品。营养
海带棕皮止水法  [PDF]
地质与勘探 , 1958,
Abstract: 我队在某钻孔涌水层进行抽水时,对该层以上含水层曾采用黄泥球止水方法来隔离.因其上部存有裂隙和溶洞,所投泥球多落于其中,故进行数次未得成功,后用棕皮海带止水的方法,始顺利地完成该项任务.其方法是:首先在127套管下端以异径接手连接一长3公尺外径为89的岩心管(如图).然后在该岩心管上紧紧缠绕干海带辫(2公分粗,以三股编成)并于辫外包一层棕皮,以15号铁丝,300~400
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