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1.
A hundred years of lectin research has led to the development of lectinology as an independent field of study. Although lectinology is in part related to immunology, fundamental differences exist. Lectins are important tools in biochemistry, histochemistry and clinical diagnosis. The essential in vivo function of lectins is to combine glycoconjugates. The function of lectins in microorganisms and in animals is partially known, whereas the function of lectins in plants is mostly unclear. Of special interest, now as before, are the toxic lectins of the ricin type consisting of an A-chain (N-glycosidase) and a B-chain (D-galactose-specific lectin).  相似文献   

2.
In the era of genetic engineering, cloning, and genome sequencing the focus of research on the genetic code has received an even further accentuation in the public eye. In attempting, however, to understand intra- and intercellular recognition processes comprehensively, the two biochemical dimensions established by nucleic acids and proteins are not sufficient to satisfactorily explain all molecular events in, for example, cell adhesion or routing. The consideration of further code systems is essential to bridge this gap. A third biochemical alphabet forming code words with an information storage capacity second to no other substance class in rather small units (words, sentences) is established by monosaccharides (letters). As hardware oligosaccharides surpass peptides by more than seven orders of magnitude in the theoretical ability to build isomers, when the total of conceivable hexamers is calculated. In addition to the sequence complexity, the use of magnetic resonance spectroscopy and molecular modeling has been instrumental in discovering that even small glycans can often reside in not only one but several distinct low-energy conformations (keys). Intriguingly, conformers can display notably different capacities to fit snugly into the binding site of nonhomologous receptors (locks). This process, experimentally verified for two classes of lectins, is termed "differential conformer selection." It adds potential for shifts of the conformer equilibrium to modulate ligand properties dynamically and reversibly to the well-known changes in sequence (including anomeric positioning and linkage points) and in pattern of substitution, for example, by sulfation. In the intimate interplay with sugar receptors (lectins, enzymes, and antibodies) the message of coding units of the sugar code is deciphered. Their recognition will trigger postbinding signaling and the intended biological response. Knowledge about the driving forces for the molecular rendezvous, i.e., contributions of bidentate or cooperative hydrogen bonds, dispersion forces, stacking, and solvent rearrangement, will enable the design of high-affinity ligands or mimetics thereof. They embody clinical applications reaching from receptor localization in diagnostic pathology to cell type-selective targeting of drugs and inhibition of undesired cell adhesion in bacterial/viral infections, inflammation, or metastasis.  相似文献   

3.
Lectins are proteins which can bind to the surfaces of animal and human cells. They are widespread in the plant and animal kingdom. Though many lectins have been isolated and characterized, and though some are extensively used as cell surface "tools", their biological role is only subject to hypotheses.  相似文献   

4.
A detailed knowledge of the mechanisms of molecular recognition is a prerequisite to rationally improved diagnostic and therapeutic procedures in diseases. In addition to sequences of amino acids, carbohydrate structures apparently store biological information that is thought to be relevant for physiologically important processes. Such ligands, namely the carbohydrate part of cellular glycoconjugates, can be recognized by specific endogenous binding proteins like lectins. If their presence can be reliably ascertained and correlated to the clinical course of the disease, e.g. in oncology, lectinology may help to define a yet undisclosed role for this class of proteins in tumor progression and spread.  相似文献   

5.
中国产品生命周期影响评价方法研究   总被引:39,自引:3,他引:39       下载免费PDF全文
讨论了确定中国产品生命周期影响评价所需的标准化基准和权重的确定方法和程序,包括产品系统环境影响潜值计算,数据标准化,加权评估 以及计算环境影响负荷和资源耗竭系数4个步骤。标准化基准采用1990年中国人均环境影响总潜值来表达,而权重采用1990年的基准与2000年中国政府的削减目标所估算的基准之间的比值计算。  相似文献   

6.
The paper reports on a comparative study of three different cases on vision and strategy development for climate change adaptation planning in (i) The South African Breede–Overberg Catchment, (ii) The Mississippi Estuary-New Orleans region and (iii) The Dutch Rhine-Meuse Estuary. The objective of the paper is twofold: to develop a better understanding of such processes and to further develop the Backcasting-Adaptive Management (BCAM) methodology. A framework for case evaluation is developed using six dimensions: (i) inputs and resources, (ii) future vision, (iii) stakeholder engagement, (iv) methodological aspects, (v) pathway development and (vi) impact. Major conclusions based on a cross-case comparison and testing propositions are (i) participatory vision development is a strong tool for climate change adaptation planning in different governance contexts and shows considerable diversity in its application in these contexts; (ii) a single, shared future vision is not a prerequisite for vision and pathway development and endorsement; (iii) broad stakeholder engagement enriches strategy development, but the involvement of marginal groups requires additional efforts and capacity building; (iv) multiple pathways and robust elements are useful but require novel expertise; and (v) more institutional embeddedness and support for participatory processes lead to better implementation of the outcomes of these processes.  相似文献   

7.
灰色生长曲线与万元产值废水量预测   总被引:2,自引:0,他引:2  
基于GIM(1)灰色线性幂函数曲线,研究开发出GPM(1)这一新的灰色生长曲线,并建立了GPM(1)简捷的参数辨别方法。研究表明,GPM(1)概念明确,结论可信,精度令人满意,比传统的皮尔生长曲线在应用上有着更大的优越性。为具有生长规律的非线性灰色环境系统的分析、预测和决策提供了新途径。  相似文献   

8.
时间分辨荧光免疫一步法检测微囊藻毒素的研究   总被引:1,自引:0,他引:1  
利用稀土元素Eu3+ 标记微囊藻毒素偶联物MCLR-BSA,在固相包被二抗的微孔板上建立了微囊藻毒素的直接竞争时间分辨荧光免疫法.条件优化后Eu3+ 标记物的稀释度为1∶50,微囊藻毒素单抗的合适浓度为100 ng/mL.该法对微囊藻毒素检测的灵敏度为0.02 ng/mL,试剂的测量范围是0.05~10 ng/mL,回收率达到94%以上.  相似文献   

9.
高锰酸钾强化三氯化铁共沉降法去除亚砷酸盐的效能与机理   总被引:12,自引:1,他引:11  
研究了不同水质条件下KMnO4强化FeCl3共沉降去除亚砷酸盐[As(Ⅲ)]的效能与机理.考察了pH值、天然有机物(NOM)等因素对As去除效能的影响.结果表明,投加KMnO4显著提高了FeCl3共沉降除砷(FCP)工艺对As(Ⅲ)的去除效能.随着Fe(Ⅲ)投量由2.0mg/L增大到8.0mg/L,对于FCP工艺,As去除率由41.3%提高到75.4%;而对于KMnO4-FeCl3共沉降除砷(POFCP)工艺,As去除率则由61.2%提高至99.3%.FCP及POFCP工艺对As的去除率均随着pH值的升高而升高;与FCP工艺比较,pH值对POFCP工艺除As效果影响较小;NOM降低了FCP工艺对As的去除率,而对POFCP工艺无明显影响.KMnO4的氧化作用是强化As(Ⅲ)去除效能的主要因素,而KMnO4的还原产物水合MnO2(s)对As(Ⅲ)也具有一定的去除能力.POFCP工艺是强化去除水中As(Ⅲ),以保障安全饮用水供给的有效方法.  相似文献   

10.
StudyoncatalystsforcombustionofleanCH_4ZhouZexing,YinLing,XuJingKesearchCenterforEco-FnvironmentalSciences,ChineseAcademyofSc...  相似文献   

11.
A mathematical model is constructed to predict frequency distributions of total suspended particulates (TSP) data for an urban area using only emissions and meteorological data as input. Predictions from this model can then be used to devise source specific emissions control strategies that avoid violations of health standards for short and long term exposure to TSP levels, both in the present situation and for future urban development. The model assumes (a) the Atmospheric Turbulence and Diffusion Laboratories (ATDL) model can be used to estimate annual arithmetic means, (b) the two-parameter lognormal distribution is representative of the TSP data, and (c) there is an inverse relationship between the percentiles of the wind speed and air pollution data sets. It is noted that only assumption (b) may not be generally applicable although the results here imply its use leads to conservative control strategies which may be reasonable first approximations. The importance of studies on the chemical composition of particulate data is stressed and shown here to be essential for accurate model predictions.  相似文献   

12.
光化学烟雾箱的表征及初步应用   总被引:5,自引:3,他引:2  
贾龙  徐永福  石玉珍 《环境科学》2011,32(2):351-361
介绍了一套自制的用于光化学臭氧和二次有机气溶胶生成研究的室内烟雾箱系统,对该烟雾箱系统进行了一系列表征实验,包括活性物种的壁损失速率常数的测定,以及由CO-NOx光氧化实验确定的反应器内·OH源,并进行了乙烯-NOx和苯-NOx光氧化的初步实验.结果表明,O3和NO2在新反应袋中壁损失受湿度影响很小,而在旧反应袋中影响...  相似文献   

13.
大亚湾沉积物中137Cs的环境容量研究   总被引:1,自引:0,他引:1  
参照水、土壤环境容量研究方法,提出沉积物环境容量的定义,并根据系统中物质平衡理论建立模型,对大亚湾沉积物中的^137Cs环境容量进行了研究,计算了大亚湾内表层沉积物中^137Cs的静容量,并选择代表性生物,计算了近岸区的年动容量和总动容量。结果表明,计算得出的环境容量接近于目前沉积物中^137Cs年输入量,在控制年限内,将沉积物的输入量控制在该环境容量范围内,是大亚湾沉积物生态系统维持目前状态,不会出现明显恶化的保证。  相似文献   

14.
黄钾铁矾能够通过吸附和共沉淀作用固定酸性矿山废水(AMD)中的重(类)金属(如砷),降低其迁移性和生物可利用性.草酸盐广泛存在于天然水环境中,其具有的羧酸官能团能改变铁矿物的稳定性,进而影响吸持的重(类)金属的再分配行为.利用水热法合成含As(V)黄钾铁矾,探究其在不同草酸盐浓度与pH条件下的溶解、重结晶和共沉淀As(V)的行为.研究结果表明,草酸盐与含As(V)黄钾铁矾表面Fe(III)活性位点配位形成的可溶性强络合物是促进矿物溶解的第一步和关键;在pH 2.5时,含As(V)黄钾铁矾的溶解速率随草酸盐浓度增加而增加,伴随大量As(V)释放到溶液,反应过程中只有少量As(V)重新吸附到固相上,这是由于草酸盐与As(V)竞争矿物表面的同一活性位点;在pH 6.5条件下,草酸盐促进含As(V)黄钾铁矾的重结晶,经X射线衍射分析表明针铁矿和纤铁矿为主要产物,能有效地吸附释放的As(V).研究结果有助于揭示在AMD环境下黄钾铁矾沉积物与含羧酸官能团有机酸共存时对As(V)的释放和固定机理,对AMD环境中As(V)污染控制有重要意义.  相似文献   

15.
黄河入河沙漠颗粒物对磷酸盐的吸附特征   总被引:1,自引:0,他引:1  
研究了黄河入河沙漠颗粒物在天然水(河水和海水)中对磷酸盐的吸附行为,用改进的Langmuir和Freundlich等温吸附模型对实验数据进行了拟合.结果表明,①改进的Langmuir等温吸附模型更适用于描述黄河入河沙漠颗粒物对磷酸盐的吸附特征,其物理意义更明确,得到的拟合参数更合理;②颗粒物对磷的最大吸附容量Qmax变化范围为41.322~357.143mg.kg-1,其中居延海颗粒物Y2的Qmax最大.Qmax与颗粒物(Y1~Y5)的有机质有着极显著的正相关关系;③除巴丹吉林沙漠颗粒物Y1外,颗粒物的临界磷平衡浓度EPC0值均大于其相应水体的磷浓度.Y1在黄河水中吸附磷的EPC0小于相应水体的磷浓度0.0100.053 mg.L-1,而在渤海海水中却大于相应水体的磷浓度0.1090.074 mg.L-1,表明Y1吸附了黄河水中的磷,进入渤海后Y1原有吸附可交换态磷NAP转移到海水中.其它颗粒物与相应水体进行磷交换的过程中存在着解吸磷的现象,具有向相应水体释放磷的能力;④黄河入河沙漠颗粒物对磷酸盐的吸附等温线是过溶液浓度轴0.00的交叉型等温线,这种新型交叉型吸附-解吸模型较好地解释了其吸附特征和天然粒子的双重性作用.  相似文献   

16.
系统比较了β-PbO2/Ti-Ti和BDD/Si-Ti两种电极体系处理实际印染行业反渗透浓水(ROC)的性能,考察了同步去除化学需氧量(COD)和总氮(TN)的动力学,以及对废水可生化性的改善情况.结果表明,BDD/Si-Ti电极体系的析氧电位(2.45V)和析氯电位(1.90V),以及阳极氧化电位和阴极还原电位的绝对值均高于β-PbO2/Ti-Ti电极体系;两种电极体系对COD以及TN的去除符合拟一级动力学,其中BDD/Si-Ti电极体系对COD去除的表观速率常数和能量利用效率均优于β-PbO2/Ti-Ti电极体系;而β-PbO2/Ti-Ti电极体系对TN去除的表观速率常数和能量利用效率更优.β-PbO2/Ti-Ti电极体系在5mA/cm2的电流密度下电解15min,可使反渗透浓水BOD/COD从0.18升至0.42(提高1.33倍),而BDD/Si-Ti电极体系仅提升0.78倍.两者相比,BDD/Si-Ti电极体系适用于矿化污染物,β-PbO2/Ti-Ti电极体系适用于改善废水可生化性.  相似文献   

17.
This paper investigates the issues involved with environmental indicator development for policy by looking at three recent examples from data and theory-driven approaches. The “Environmental Sustainability Index 2001” report from World Economic Forum, YCELP and CIESIN is taken as an example of the data-driven approach, whereby data availability is the central criterion for indicator development and data is provided for all selected indicators. The other two examples are theory-driven, whereby, the focus is on selecting the best possible indicators from a theoretical point of view and data availability is considered only one of the aspects involved. These examples are the Heinz Center’s1999 report on the “State of the Nation’s Ecosystems” and the US National Research Council (NRC) report on “Ecological Indicators for the Nation”. The reports and approaches are discussed and compared in order to determine their strengths and weaknesses. From this lessons are drawn for future environmental indicator work as a basis for policymaking. In the conclusions four important issues are addressed: (1) data availability; (2) ecosystem specificity of indicators; (3) spatial and conceptual aggregation of indicators and (4) baseline or reference values for indicators. For each of these issues recommendations are made.  相似文献   

18.
介绍了国家标准GB“水质烷基汞的测定气相色谱法”制订任务的由来及背景:制订标准的依据及技术路线的选择;分析方法的质量保证(QA)和质量控制(QC)的重要性和意义。讨论了本项国家标准的3个显著特点:本项国家标准的建立是国际上资产将巯基棉吸附技术纳入国家级标准分析方法,在国内现有的GB中,首次引入QA和AC:该标准方法的适用范围不仅限于水质,可扩展到各种环境样品。  相似文献   

19.
此文利用主应力法推导出圆管空拔壁厚变化量解析式。该式计算结果与以定常三维流动上界解析同类问题结果相接近,且表达式简单,也与拔管的实验结果相一致。因而,可在圆管空拔壁厚计算时推广应用。  相似文献   

20.
研究了在生成高铁酸盐反应过程中K+对Fe(Ⅵ)的稳定促进作用和机理.结果表明,当反应温度大于50℃时,K+比Na+更有利于高铁酸盐的生成.K+促进高铁酸盐溶液生成的最佳反应温度为65℃.在生成高铁酸盐反应过程中,增加K+浓度能提高高铁酸盐的产率,并且随着硝酸铁投加量的增加,K+影响显著.在硝酸铁投加量为85 g/L时,采用4.4 mol/L KOH制备的Fe(Ⅵ)浓度为0.05 mol/L;加入2 mol/L K+后,Fe(Ⅵ)浓度增加到0.15 mol/L.K+对高铁酸盐溶液生成浓度的影响在硝酸铁投加量大于75 g/L,反应温度低于55℃,ClO-浓度低于1.16 mol/L时较为显著.K+在一定程度上可替代部分碱度,降低OH-用量.在反应过程中K+能包裹在FeO2-4周围,减少Fe3+与FeO2-4接触,从而减缓Fe3+对FeO2-4的催化分解作用;同时K+能与FeO2-4生成K2FeO4晶体沉淀析出,降低溶液中FeO2-4浓度,Fe(Ⅵ)分解速率减缓,稳定性增加,Fe(Ⅵ)生成浓度增加.  相似文献   

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