Cloning and characterization of a plasmid DNA from anacystis nidulans 6301

A plasmid DNA of Anacystis nidulans 6301 was isolated by CsCl-EtBr centrifugation. The Mr of the plasmid, named pBA1, was estimated to be 5.04 +/- 0.26 X 10(6) by electron microscopic analysis and 5.2 X 10(6) by agarose gel electrophoresis. The pBA1 DNA was opened at a unique site with BamHI and cloned in pBR322 vector propagated in Escherichia coli HB101 cells. The recombinant plasmid, named pBAS18, was digested with various restriction endonucleases and its cleavage map was constructed. Based on this result, the cleavage map of the pBA1 plasmid is presented.     

Parameter identification of the calvin photosynthesis cycle

Summary This article is concerned with the determination of kinetic parameters of the Calvin photosynthesis cycle which is described by seventeen nonlinear ordinary differential equations. It is shown that the task requires dynamic data for several sets of initial conditions. The numerical technique is based upon an algorithm for non-linear optimization and Gear's numerical integration scheme for stiff systems of differential equations. The sensitivity of the parameters to noise in the data is tested with a method adapted from Rosenbrook and Storey. A preliminary set of parameters has been obtained from a preliminary set of experimental data. The numerical methods are then tested with synthetic data derived from these parameters. The mathematical model and the results obtained in the simulation are used as an aid in designing new experiments.     

The acetylene reduction technique as an assay for nitrogenase activity in the methane oxidizing bacterium Methylococcus capsulatus strain bath

The use of acetylene as a convenient assay substrate for nitrogenase in methane oxidising bacteria is complicated by the observation that it is a potent inhibitor of the methane monooxygenase enzyme in both whole cells and cell-free extracts. If the cells were provided with alternative oxidisable carbon substrates other than methane then nitrogen fixing cells would reduce acetylene to ethylene. Hydrogen gas also served as an oxidisable substrate in the assay. Nitrous oxide, which is reduced by nitrogenase to N₂ and H₂O, was not an inhibitor of methane monooxygenase function and could be used as a convenient assay substrate for nitrogenase. Reduction of both substrates by whole cells showed similar response to oxygen in the assay system and in this respect Methylococcus resembles other free living nitrogen fixing aerobes.     

城市可持续规划中的生态敏感区避让分析——以丽江市为例

为促进城市可持续发展,在科学合理规划城市空间格局的基础上,应突出强调保护原有特色生态环境要素,保育生态系统服务功能和原住民人居环境。作为世界文化遗产,丽江城市面貌在过去数十年发生了深刻变化,城市用地显著扩张,同时严峻的环境问题对城市可持续发展提出挑战。以丽江市为例,选取对其发展影响深远的水系元素、噪声环境因子和森林火灾3个关键生态敏感因子,提出通过分析这类生态敏感区在城市规划过程中的避让方法、程度,区划城市规划基本空间格局,以避免城市未来因生态环境问题突出而制约其发展的规划用地思路。结果表明,丽江城区周边湖泊水系、古城内部及周边原住民人口密集区都是保障城市可持续发展的生态保护重点地区,在城市用地规划中必须予以避让;该区域面积为147.2 km2,占研究区面积的11.1%。同时,明确给出了规划用地的具体空间控制范围和相应的避让原则。     

SWAT模型对景观格局变化的敏感性分析——以丹江口库区老灌河流域为例

景观的空间配置与类型组成能够对流域的产流、产沙及非点源污染产生影响。在以往SWAT模型研究中,往往默认水文模型考虑了该影响。为分析SWAT模型对不同景观格局变化的敏感性,根据老灌河流域2000年土地利用在各子流域的组成,模拟研究区更为破碎、复杂的景观空间配置,通过设置多套试验参数,利用SWAT模型生成基于不同景观格局的模拟结果。结果表明,SWAT模型不能反映除坡度和面积变化之外的景观水平下各斑块之间因景观空间格局改变对流域产流、产沙以及非点源污染的影响;模型通过其他参数的调整,弥补了模型分析数据的不足,使实测数据与模型部分结果高度吻合。这表明,一个能够反映流域部分水文特征的SWAT模型,未必是对研究区真实情形的模拟,而是各个参数间平衡的结果。因此,在利用SWAT模型分析模拟景观变化时,不应默认模型能够模拟景观空间格局改变对流域水文过程的影响,同时研究者可以通过划分坡度带,提高模型对不同坡度土地利用的敏感性。     

A 3D doubly sensitivity enhanced X-filtered TOCSY-TOCSY experiment

We present a 3D double sensitivity enhanced X-filtered homonuclear TOCSY-TOCSY experiment for the assignment of unlabeled molecules complexed to labeled protein- or nucleic acid-domains. The resulting spectrum is clean, can be measured in a reasonable amount of time and allows for increased resolution of overlapping resonances when compared to 2D methods. The 3D X-filtered TOCSY-TOCSY allows for assignment in cases where the size or the composition of the unlabeled molecule results in a high degree of overlap.     

An application of the theoretical group methods to modeling of complex systems

The applicability of theoretical group methods to studying complex physical and biological systems with the potential of self-organization was demonstrated. The problem of calculating climate sensitivity parameters taking into account the cyclone-anticyclone structure of the atmosphere optically dense in the infrared region is considered as an example.     

八种昆虫离体细胞系对灭多威农药的敏感性研究

采用ＭＴＴ法,研究了灭多威农药对八昆虫离体细胞系敏感性的差异。结果显示,同一浓度处理下,不同细胞系细胞病变的程度不同,敏感性差异很大。ＬＣ５０值在１０＾２－１０＾５μｇ／ｍｌ范围内变化,其中,白纹伊蚊细胞系是最敏感的,而小菜蛾细胞系几乎不敏感。     

三氟氯氰菊酯对棉铃虫神经细胞延迟整流钾电流的抑制作用

用膜片钳技术首次研究了三氟氯氰菊酯对离体培养的棉铃虫中枢神经细胞延迟整流钾通道电流的影响。结果表明,药物作用前有81%和39%的细胞的通道分别在-30 mV 和 -40 mV 激活（n=21）。三氟氯氰菊酯（10^-5 mmol/L）作用15 min后,有63%和38%细胞的通道分别在-40 mV 和 -50 mV 激活（n=8）;作用1 min后电流幅值明显降低,抑制率达到了37.7%（n=19）;加药后激活曲线明显左移且Vh 值变化显著,但k值没有明显变化。实验结果说明,三氟氯氰菊酯作用后,通道更容易激活,但显著抑制电流峰值,导致神经敏感性降低,棉铃虫中枢神经细胞钾通道也是拟除虫菊酯类药物的作用靶标之一。