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《小哥白尼(野生动物画报)》2011,(5)
哎呀呀,这个世界乱套了!大人变成了小孩,小孩变成了大人。现在,终于轮到各位小酷想家来当家做主了,快来看看他们都有什么出色的表现吧!看到爸妈变成了小孩,我立马学着他们的样子,下达了第一道命令:写作业去!我想他们一定会哭的,因为老师留的作业实在是太多了。新浪YOYO 相似文献
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自从1953年DNA双螺旋结构发现以后,紧接着对生物大分子的各种新发现层出不穷,生物学可谓就进入了分子生物学的时代,它使人们对生物学的认识提高到了一个新的水平,也开拓了新的领域.当然,分子生物学也使进化论的研究转入了一个更精细的水平,解决了进化论中一些争论的问题,同时也提出了一些新的研究思想和观点. 相似文献
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2004年11月,一个14岁的孩子揪住了所有人的心。他叫梁攀龙,湖南省怀化人。11月11日,他爬进客机起落舱,从昆明飞到了重庆。在1个多小时的飞行中,梁攀龙蜷缩在起落舱中,经历了噪音、寒冷、缺氧的考验,如今依然健康地活着。而和梁攀龙一起爬进起落舱的束清,就没有那么幸运了,飞机起飞时,他被甩了出去。昆明机场的工作人员发现束清的时候,他已经没有了呼吸。 相似文献
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远程教育培训给生物教学带来新的生机。夯实了专业知识,梳理了生物知识,使我认识到应该如何把握生物课堂教学,提高了课堂教学设计能力,凝聚了生物教师的力量,使老师们学到了很多知识和教学技能,解决了平时教学中的一些难题,提升了生物的教学水平。 相似文献
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为了解决龙眼园的郁闭问题,提高龙眼的产量和品质,该文以桂香龙眼品种为材料,研究了扁开心形、开心形、自然圆头形三种不同树体结构对树体光照强度、叶片、根系、果实的影响。结果表明:扁开心形显著改善了树冠和果园通风透光环境,提高了叶绿素含量,增大了叶面积,提高了PSⅡ系统活性和开放程度,调节了光合机构的自我保护机制,改善了荧光参数,从而提高了果实品质;扁开心形、开心形、对照的单株产量分别是19.90、17.00、15.60 kg,单果重分别是10.24、10.07、7.64 g;扁开心形和开心形可食率比对照分别提高了4.20%、4.40%,可溶性固形物含量分别提高了12.16%、12.55%;扁开心形比开心形以及对照的表层根有所上浮,促进了果树的生殖生长,显著扩大了根系的分布深度,扩大了根系对营养物质以及水分的吸收。扁开心形是一种高光效的树形,应在生产上加以推广。 相似文献
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The chemistry of boron and its speciation in plants 总被引:11,自引:0,他引:11
The chemistry and usage of B, as well as its speciation in plants, are reviewed. In the context of biology, the chemistry of the surprisingly rare element B is dominated by B-oxygen compounds. The occurrence, distribution and chemistry of these compounds are briefly described. In addition, the chemistry involved in the interaction of B–O compounds with naturally occurring molecules, particularly polyhydroxy compounds, is summarised. The essentiality of B in plants has been known for 75 years, but the biomolecule(s) with which it interacts to cause its essential function(s) remain largely unknown, although many have been suggested. Recent research on the complexation, isolation and partial characterisation of B complexes of polysaccharides, diols, and hydroxyacids is outlined. The particular importance of B interactions with cell wall components, membranes, enzymes, sugars, and polyols is discussed. 相似文献
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Beta-C-glycosiduronic acid quinones and beta-C-glycosyl compounds have been synthesized as sugar-based PTP1B inhibitors. Benzoyl protected quinone derivatives (14 and 35) as well as aryl beta-C-glycosyl compounds (18, 22, 23 and 34) showed IC(50) values of 0.77-5.27 microM against PTP1B, with compounds 18 and 23 bearing an acidic function being the most potent. 相似文献
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Dziadulewicz EK Brown MC Dunstan AR Lee W Said NB Garratt PJ 《Bioorganic & medicinal chemistry letters》1999,9(3):463-468
The Bradykinin B2 receptor antagonist HOE 140 (D-Arg-Arg-Pro-Hyp-Gly-Thi-Ser-D-Tic-Oic-Arg) has been used as a template for the de novo design and synthesis of a small number of non-peptide lead compounds based on the 1,4-benzodiazepin-2-one framework. Two of the compounds have been found to exhibit moderate K(i) values of 8.9 and 9.2 microM at the human Bradykinin B2 receptor. 相似文献
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Aino Rummukainen Riitta Julkunen-Tiitto Mikko Räisänen Tarja Lehto 《Plant and Soil》2007,292(1-2):13-23
The increase in concentrations of phenolic compounds in boron (B) deficiency has been demonstrated in many herbaceous plant
species, but information on woody plants is scarce. It has been suggested that accumulation of phenolic compounds plays a
role in the development of cold hardiness in herbaceous plants but also that B deficiency decreases winter hardiness. Here
we study the effects of B nutrition on phenolic compounds in Norway spruce (Picea abies L.) in the course of cold acclimation. Phenolic compounds were analysed in Norway spruce seedlings from three different B-fertilisation
treatments in two harvests: non-acclimated and cold-acclimated seedlings. Norway spruce phenolic compounds consisted mainly
of condensed tannins. During B deficiency, condensed tannins and monocoumaroyl–astragalin der. 1 increased in non-acclimated
seedlings. The increase in tannins was 21%, which was nearly significant. However, the effect of B on phenolic compounds was
almost absent in cold-acclimated seedlings. The condensed tannin concentration increased much more with time in the simulated
autumn than due to B deficiency, and we conclude that the B effect was probably not large enough to be important for the hardening
of the seedlings. The total phenolic concentrations more than doubled during the course of cold hardening suggesting that
phenolics have a role in the winter hardiness in Norway spruce. 相似文献
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Cathepsins have emerged as promising molecular targets in a number of diseases such as Alzeimer’s, inflammation and cancer. Elevated cathepsin’s levels and decreased cellular inhibitor concentrations have emphasized the search for novel inhibitors of cathepsins. The present work is focused on the design and synthesis of some acetophenone phenylhydrazone based pyrazole derivatives as novel non peptidyl inhibitors of cathepsins B, H and L. The synthesized compounds after characterization have been explored for their inhibitory potency against cathepsins B, H and L. The results show that some of the synthesized compounds exhibit anti-catheptic activity with Ki value of the order of 10−10 M. Differential inhibitory effects have been observed for cathepsins B, H and L. Cathepsin L is inhibited more pronounced than cathepsin B and cathepsin H in that order. 相似文献
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The behaviour of boron (B) and its fate in the environment remains in many respects obscure. The major B sources and fluxes
seem to have been identified, although there are many uncertainties about the magnitude and importance of each; published
evaluations vary greatly. Little is known about B speciation of living matter-bearing formations, i.e. soils, natural waters,
and sediments. Many authors suppose that B in nature occurs only as oxo-compounds, although, natural inorganic and organic
B compounds and complexes have been described. Moreover, the most common approach to B biogeochemistry in terms of inorganic
B compounds (as boric acid and borates) seems to oversimplify the matter. Data on the physiological functions of B are fragmentary
and often contradictory. Some data exists on endemic symptoms and diseases among humans and grazing cattle that are supposedly
triggered by B abundance in the natural environment. Unfortunately, the published data are scarce and vague. In this paper,
we review the up-to date references on B sources, turnover, and speciation in the environment and the element potential impact
on health. 相似文献
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The absolute configurations of three synthesized anthracycline analogues have been determined using vibrational circular dichroism (VCD) spectroscopy and the density functional theory (DFT) calculations. The experimental VCD spectra of the three compounds have been measured for the first time in the film state, prepared from their CDCl3 solutions. Conformational searches for the monomers and some dimers of the three compounds have been performed at the DFT level using the B3LYP functional and the 6‐311G** and 6‐311++G** basis sets. The corresponding vibrational absorption and VCD spectra have been calculated. The good agreement between the experimental and the calculated spectra allows one to assign the absolute configurations of the three compounds with high confidence. In addition, the dominant conformers of the three compounds have also been identified. Chirality, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
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Bioactive apocarotenoids from Tectona grandis 总被引:1,自引:0,他引:1
The bioactive fractions of Tectona grandis have yielded seven apocarotenoids, two of which have been isolated for the first time as natural products (tectoionols A and B). The chemical structures were determined through 1D and 2D nuclear magnetic resonance experiments. The absolute configuration of tectoionol A was determined using a modified Mosher methodology. Some NMR assignments for the compounds 9(S)-4-oxo-7,8-dihydro-beta-ionol and 3beta-hydroxy-7,8-dihydro-beta-ionone have been corrected on the basis of g-HSQC and g-HMBC experiments. The general bioactivities of isolated compounds have been studied using etiolated wheat coleoptiles. Those compounds that presented higher levels of activity were assayed on standard target species (Lactuca sativa, Lycopersicum esculentum, Lepidium sativum and Allium cepa). 相似文献
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Studies on the biosynthesis of avermectins 总被引:2,自引:0,他引:2
To elucidate the pathway of avermectin biosynthesis, the biosynthetic relationships of avermectins A1a, A2a, B1a, B2a, and their respective monosaccharides and aglycones were studied. 14C-labeled avermectin compounds prepared from [1-14C]acetate were fed to Streptomyces avermitilis strain MA5502 and their metabolites were determined. Two furan ring-free aglycones, 6,8a-seco-6,8a-deoxy-5-keto avermectin B1a and B2a, have been isolated from the fermentation broth of a blocked mutant of S. avermitilis. Addition of the compounds and a semisynthetic compound, 5-keto avermectin B2a aglycone, to the fermentation medium of a second blocked mutant established that the two compounds are intermediates in the avermectin biosynthetic pathway immediately preceding avermectin aglycones. 相似文献
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Seo C Choi YH Sohn JH Ahn JS Yim JH Lee HK Oh H 《Bioorganic & medicinal chemistry letters》2008,18(2):772-775
Ohioensins F and G (1 and 2), two new benzonaphthoxanthenones, have been isolated from the MeOH extract of Antarctic moss Polytrichastrum alpinum by various chromatographic methods. The structures of these compounds were determined mainly by analysis of NMR spectroscopic data. The known compounds ohioensins A and C (3 and 4) were also obtained. Compounds 1-4 showed potent inhibitory activity against therapeutically targeted protein tyrosine phosphatase 1B (PTP1B). Kinetic analysis of PTP1B inhibition by ohioensin F (1) suggested that benzonaphthoxanthenones inhibited PTP1B activity in a non-competitive manner. 相似文献