10种黄酮类抗氧化剂活性差异的理论阐释

借助理论方法,包括结构－活性关系（ＳＡＲ）和最子化学计算阐释了１０种黄酮类抗氧化剂清除自由基活性的痉异。发现ＳＡＲ可以定性地解释抗氧化剂的活性差异。而半经验量子化学方法ＡＭＩ计算的理论参数△ＨＯＦ（抗氧化剂与其抽氢反应产生的自由基的和成热之差）可以对此给出进一步的解释。△ＨＯＦ与抗氧化清除自由基速率常数的对数还有一定相关性,相关系数为－０．７５２３。因此理论方法在解释抗氧化剂的活性差异方面是有效的     

Molecular replacement studies on crystal structure of allophycocyanin from red algaePorphyra yezoensis

Using the crystal structure of allophycocyanin from cyanobacterium Spirulina platensis (APC-SP) as a search model, the crystal structure of allophycocyanin from red algae Porphyra yezoensis (APC-PY) has been studied by molecular replacement methods. The APC-PY crystals (Form 3) belong to the space group of R32, cell dimensions a = b = 10.53 nm, c = 18.94 nm, α =β = 90°, γ= 120°; there is one αβ monomer in each crystallographic asymmetric unit in the cell. The translation function search gave a unique peak with a correlation coefficient (Cc) of 67.0% and an R-factor of 36.1 % for reflection data from 1.0 to 0.4 nm. Using the results by molecular replacement, the initial model of APC-PY was built, and the coincidence of the chromophore in APC-PY initial model with its 2Fo-FC OMIT map further confirms the results by molecular replacement.     

元宝枫苗木的水力结构特征

在温室条件下,控制不同干旱梯度,用改良的冲洗法测定了4年生元宝枫苗木的水力结构参数．研究表明,随着小枝水势的降低,水力结构各参数随茎段功能木质部直径的变化可以用不同的方程来模拟;导水率的大小受茎段所在区域的影响,限速区的导水率明显低于非限速区,限速区的存在对苗木个体的生存竞争有利．导水率、比导率和叶比导率都和功能木质部直径和小枝水势呈明显的正相关．较粗茎段的叶比导率远高于多次分枝的未端细小分枝,有利于苗木在干旱时保存那些光合积累较大的器官．在落叶之前,相同直径枝条的胡伯尔值随小枝水势的变化很小,说明苗木水分胁迫主要源于木质部空穴和栓塞．     

生态环境需水量研究进展

主要从概念、分类以及计算方法等方面论述了生态环境需水量的国内外研究动态．目前．国外对生态环境需水量的研究主要集中在河流方面,并已形成一套比较成熟的计算方法体系;国内则主要集中于水资源缺乏的西北内陆河流域和黄河、海滦河流域的陆地和河流方面的研究．总的来说,国内外对生态环境需水量的研究已经取得了一定的成果,但仍然存在着许多尚待进一步研究的问题：(1)强化生态环境需水量的基础理论(概念、分类和计算方法等)研究;(2)加强对生态环境需水量的内在与外在影响因素及保障生态环境需水量的途径与措施等方面的研究;(3)拓展生态需水量的应用性研究等。     

蔬菜中农药残留检测技术研究进展

对目前蔬菜中农药残留分析检测方法及其前处理过程以及快速检测技术作了综述。固相萃取(SPE)、超临界流体萃取(SFE)等新的萃取方法已逐渐代替了液-液萃取(LLE)等传统提取方法。色谱技术是农药残留分析中的重要手段。毛细管气相色谱(CGC)、高效液相色谱(HPLC)及其联用技术是现阶段农药残留分析中的主要检测方法。并指出了今后该领域的研究方向。     

Estimation of soil algal biomass in salinized irrigation land: a comparison of culture dilution and chlorophyll a extraction methods

Two representative methods for quantitative estimation of soil algae, the culture dilution method and chlorophyll a extraction, were compared using soil samples collected from irrigation land in the flood plain of the River Ili, Kazakhstan, where the distribution of soil algae had been studied in the previous year. The estimate by the culture dilution method was almost the same as in the previous year, except for one site, which was enclosed by shrubs of sakusaul, Haloxylon aphyllum (Minkw.) Iljin. The important role of wind in transport of airborne algal cells was pointed out. There was a significant correlation (p<0.001) between the logarithm of the number of colonies by the culture dilution method andthe logarithm of the concentration of chlorophyll a, when data from all samples were analyzed. However, no significant correlation was observed with the data of cropland sites alone. Furthermore, the seasonal variations of both values at each site did not necessarily agree with each other. One reason for the inconsistency may have been the over estimation of chlorophyll a caused by inclusion of litter from vascular plants. Other reasons may relate to differences between the methodologies. The density of soil algae estimated by culture dilution reflects the algal biomass in a certain previous period of time. Therefore, it is suggested that the method is suitable for spatial, but not for seasonal studies. This revised version was published online in August 2006 with corrections to the Cover Date.     

Phytoplankton assemblage structure and dynamics as indicator [-2pt] of the recent trophic and biological evolution of the western basin of Lake Como (N. Italy)

We studied the phytoplankton assemblage of the western basin of Lake Como (Northern Italy) during 1997. The phytoplankton assemblage was composed of 65 taxa, belonging to six taxonomic groups. Chlorophyta were represented by the highest number of taxa (28) followed by Bacillariophyceae (17), Cyanoprokaryota (9), Dinophyceae (6), Chrysophyceae (3) and Cryptophyta (2). The total assemblage density and biomass ranged from 902 ind ml^–1 and 134.5 mm³ m^–3 in February to 58 766 ind ml^–1 and 9360 mm³ m^–3 in October. The density and biomass variation at three stations showed a common pattern, with higher values in the southern part of the basin where TP concentrations were always greater. The phytoplankton succession was analysed by cluster analysis (average linkage clustering) and non-metric multidimensional scaling (NMDS) ordination, both applied to a dissimilarity matrix obtained from a calculation of the Bray–Curtis index. In general, the seasonal succession followed a simple pattern, with a clear spring phase. These results are discussed considering the trophic evolution of the lake and its recent colonization by Dreissena polymorpha.     

基于GA-BP人工神经网络的樟树林土壤呼吸对施氮响应的研究

目前开展的施氮对土壤呼吸影响研究大多基于实验观测结果,受实验地自然条件的限制,不能研究在一定条件范围内土壤呼吸对施氮响应的连续变化。通过喷洒NH_4NO_3水溶液,设置对照(C,no N added),低氮(L,5 gNm~(-2)a~(-1)),中氮(M,15gNm~(-2)a~(-1)),高氮(H,30 gNm~(-2)a~1)4种处理水平,使用GA-BP人工神经网络建立樟树林土壤呼吸对施氮响应的模型,并将模拟结果使用响应曲面法展示,研究土壤呼吸对施氮响应的变化。研究结果表明,施氮对樟树林土壤呼吸既有抑制作用又有促进作用,其程度是由土壤温湿度条件决定的,总体上使得施氮对土壤呼吸在低土壤湿度的条件下主要表现为促进作用,在高土壤湿度条件下主要表现为抑制作用,在一部分土壤温湿度组合下表现为无明显作用。GA-BP人工神经网络模型以其特性,可以模拟土壤呼吸对施氮响应的连续变化,并在一定程度上解释了施氮量、土壤呼吸、土壤温度和土壤湿度之间复杂的数学关系。     

反例微视频教学法在“微生物学实验”课程中的实践研究

"微生物学实验"是生物类相关专业的一门必修课程,该课程的开展对提高学生实验技能和理解微生物学知识原理至关重要。因此,不断探索和改进实验课程教学方法、减少学生的错误实验操作、提高实验课堂教学效率是任课教师的基本任务。反例微视频教学法是将传统的案例教学法、反例教学法和当下流行的微课程相结合的一种教学方法。本文阐述了该教学法的原理、基本操作流程、课堂应用效果和存在的问题。该教学法的实施能较好地提高实验课堂效率,大幅减少学生错误实验操作的次数,值得在本科生物类实验课堂中进行推广。