CYCLIC PEPTIDE HEPATOTOXINS FROM FRESH-WATER CYANOBACTERIAL (BLUE-GREEN-ALGAE) WATERBLOOMS COLLECTED IN CENTRAL CHINA

Toxic cyanobacteria (blue-green algae) waterblooms have been found in several Chinese water bodies since studies began there in 1984. Waterbloom samples for this study contained Anabaena circinalis, Microcystis aeruginosa and Oscillatoria sp. Only those waterblooms dominated by Microcystis aeruginosa were toxic by the intraperitoneal (i.p.) mouse bioassay. Signs of poisoning were the same as with known hepatotoxic cyclic peptide microcystins. One toxic fraction was isolated from each Microcystis aeruginosa sample. Two hepatotoxic peptides were purified from each of the fractions by high-performance liquid chromatography and identified by amino acid analysis followed by low and high resolution fast-atom bombardment mass spectrometry (FAB-MS). LD50 i.p. mouse values for the two toxins were 245-mu-g/kg (Toxin A) and 53-mu-g/g (Toxin B). Toxin content in the cells was 0.03 to 3.95 mg/g (Toxin A) and 0.18 to 3.33 mg/kg (Toxin B). The amino acid composition of Toxin A was alanine [1], arginine [2], glutamic acid [1] and beta-methylaspartic acid [1]; for Toxin B it was the same, except one of the arginines was replaced with a leucine. Low- and high-resolution FAB-MS showed that the molecular weights were 1,037 m/z (Toxin A) and 994 m/z (Toxin B), with formulas of C49H76O12N13 (Toxin A) and C49H75O12N10 (Toxin B). It was concluded that Toxin A is microcystin-RR and Toxin B is microcystin-LR, both known cyclic heptapeptide hepatotoxins isolated from cyanobacteria in other parts of the world. Sodium borohydride reduction of microcystin-RR yielded dihydro-microcystin-RR (m/z = 1,039), an important intermediate in the preparation of tritium-labeled toxin for metabolism and fate studies.

Self-ordering of quasi-quantum wire in InAlAs/AlGaAs multilayer nanostructure and its optical anisotropy

Self-ordering of quasi-quantum wires in multilayer InAlAs/AlGaAs nanostructures grown by molecular beam epitaxy is identified. The chain-like structures along the [1 (1) over bar 0] Of direction formed by coalescence of quantum dots were observed. The photoluminescence of the nanostructures is partially polarized along the [1 (1) over bar 0] direction. The polarization ratio depends on the wavelength and the maximum polarization is on the lower energy side. The maximum polarization increases from 0.32 at 10 K to 0.53 at 100 K, and the energy position of maximum polarization moves near to PL peak with increasing temperature. They are all related to the existence of isolated islands and quasi-quantum wires in our sample. This result provides a novel approach to produce narrow quantum wires. (C) 2000 Elsevier Science B.V. All rights reserved.

轻小型CCD相机光学系统设计

国家重点基础研究发展计划( 2009CB724006) 资助

CSRe减速模拟

对兰州重离子加速器冷却储存环实验环中束流的减速过程进行了模拟研究 ,采用变换谐波的方式将粒子减速到较低能量 ,以适应高精度原子物理实验的需要 .根据模拟结果得到了减速过程各个时刻粒子在纵向相空间分布 ,并给出了高频参数在减速过程中的变化曲线 .

黄旗海沉积岩芯烧失量变化曲线：冰后期环境演变的有效代用指标

IEECAS SKLLQG

中能重离子碰撞中带电粒子多重性的同位旋效应

利用兰州4π带电粒子探测器阵列测量带电粒子多重性,研究了55MeV/u ~(40)Ar+~(58,64)Ni核反应中He和中等质量碎片的产额与反应系统同位旋的关系,以及这种同位旋效应与反应系统的碰撞参数(即碰撞的激烈程度)、系统的激发能的变化关系,对两个反应系统,观察到带电粒子多重性中He的比分随带电粒子多重性的增加而增大,带电粒子多重性中IMF的比分随带电粒子多重性的增加而先增大,后减小的规律.两个反应系统虽然具有相同的核电荷数,但轻粒子He和中等质量碎片在多重性中的比分有明显的同位旋相关性。

水土保持科研与管理专家王万忠研究员

王万忠研究员 ,男 ,生于 1 95 2年 ,陕西省临潼县人。 1 976年毕业于陕西师范大学地理系 ,分配到中国科学院水利部水土保持研究所工作至今。 1 988年担任科研处处长 ,1 991年任中国科学院黄土项目办公室副主任 ,1 994年 9月 ,以高级访问学者身份赴日本东京大学、宫崎大学访问 ,1 995年任副所长 ,现任西北农林科技大学党委副书记 ,硕士研究生导师。王万忠研究员 ,长期从事土壤侵蚀与水土保持研究工作 ,曾主持国家“八五”攻关专题“黄土高原区域水土保持与农业发展综合研究”,国家“九五”攻关子专题“水土保持效益区域性评估及主体措施配置”,中国科学院知识创新项目子专题“高强度治理下黄土高原水土流失预测”以及“中国降雨侵蚀力研究”等项目。其中国家“八五”攻关专题“黄土高原区域水土保持与农业发展综合研究”获 1 998年中国科学院科技进步二等奖 ,他本人也被国家计委、国家科委及财政部授予“八五”国家科技攻关先进个人 ,受到江泽民总书记的接见。出版专著 2部 ,参编专著 2部 ,发表论文 2 0余篇 ,其中专著《黄土高原降雨侵蚀产沙与黄河输沙》、《黄土高原降雨侵蚀产沙数据图集》,以及论文“黄土地区...

延安试区土壤干层现状分析

近年来 ,以林草地地力衰退为特征的人工林草地土壤退化日趋严重 ,其中以土壤水分严重亏缺为特征的土壤干化现象愈益引起了人们的重视。土壤干化的直接后果是形成土壤干层 ,导致土壤退化 ,植物生长速率减缓 ,群落衰败以至大片死亡 ,严重地威胁到中国中北方地区特别是黄土高原地区生态环境的建设。因此 ,研究和解决土壤干层问题已成为黄土高原植被建设的迫切任务。根据现有土壤水分资料 ,初步分析了延安试区植被下的土壤干层现状 ,对不同林草植被下的干层状况做了比较 ,并提出了解决土壤干层问题的意义