光系统Ⅱ抑制剂三维定量构效关系模型

光系统Ⅱ（ＰＳⅡ）抑制剂通过抑制光合作用系统Ⅱ的电子传递使杂草因光合作用中断而死亡。本文选择不同骨架结构的ＰＳⅡ抑制剂,由限定性构象搜索方法确定了重叠规则,采用比较分子场分析方法进行了三维定量构效关系研究。提出了具有较强预测能力的构效关系模型。     

光系统Ⅱ抑制剂的三维构效关系和相关性研究

光系统Ⅱ（ＰＳＩＩ）抑制剂要导致ＰＳＩＩ反应中心的电子传递受阻,被认为是重要的除草剂。近年来发现许多合物都有希尔反应抑制活性。本文利用比较分子场方法,在药效团模型基础上,对不同系列的光系统ＩＩ抑制剂的结构和活性关系进行了分析和讨论。     

酪氨酸激酶抑制剂的虚拟受体模型方法研究

利用柔性原子受体模型(FLARM)方法对一系列的异黄酮和喹诺酮衍生物表皮生长因子受体酪氨酸激酶抑制剂进行了三维定量构效关系研究,得到了合理的构效关系模型。FLARM方法的计算结果还给出了虚拟的受体模型,该模型说明了抑制剂与受体之间可能的相互作用。这些相互作用包括两个氢键和一个硫-芳香相互作用,以上结果仅仅是由7个化合物得到的。     

新型二芳基取代-1,2,4-三唑类化合物的抗炎构效关系和分子对接研究

目的:建立新型二芳基取代-1,2,4-三唑类化合物的定量构效关系,设计新型COX-2抑制剂.方法:采用PM3半经验量子化学法全优化18种二芳基取代-1,2,4-三唑类选择性环氧合酶(COX-2)抑制剂的结构,从数据中搜寻或计算它们的226种参数,利用逐步回归法,建立经典结构-活性关系(2D-QSAR);用Autodock对接软件研究二芳基取代-1,2,4-三唑类化合物与环氧合酶(COX-2)的对接,分析该类化合物与环氧合酶在复合物的立体结构以及分子对接自由能与抑制活性的关系.结果:建立合理二芳基取代-1,2,4-三唑类化合物COX-2抑制剂定量构效关系,表明活性二芳基取代-1,2,4-三唑类选择性环氧合酶(COX-2)抑制剂具有类似塞来昔布等三环类环氧合酶-2抑制剂的立体结构,并且对接自由能与抑制剂活性有较好的相关性.结论:所得的模型可以解释已有的构效关系,而且预测同类化合物能力较好,可指导设计新抑制剂.     

嘧啶硫苯甲酸类的三维构效关系研究

利用比较分子场分析（ＣｏＭＦＡ）对１６嘧啶硫苯甲酸类化合物进行了三维定量构效关系研究，得到了具有较强预测能力的ＱＳＡＲ模型。研究结果表明袖章效应是影响构效关系的主要因素，为更好地解释结构与活性的关系，设计新型嘧啶苯甲酸类除草剂提供了有益的指导。     

粗糙集-比较残基相互作用分析法研究HIV整合酶抑制剂的构效关系

目的;结合粗糙集(RS)理论和比较残基相互作用(CoRIA)研究HⅣ整合酶抑制剂的构效关系(SAR);方法:选择一系列影响抑制剂与IN蛋白结合的关键残基,采用其与抑制剂的非键作用力数据(电子作用力和范德华作用力),利用RS理论建立了决策规则,分析了相应的构效关系。结果:总体表明化合物与Asp64、Thr66、Asp116、G1u152的作用力越大,药物活性越高,Lys159的作用正好相反。同时不同作用力之间存在拮抗作用,违反上述规律,影响抑制剂的活性。结论:本文的结果对研究抗HIv药物的药理、作用机制及整合酶抑制剂的开发均有一定的意义。     

ASP应用系统性能可扩展性设计策略

ＡＳＰ是微软系统性能Ｗｅｂ应用的基石,就单个ⅡＳ而言,ＡＳＰ已使微软的Ｗｅｂ性能达到世界顶尖。如何进一步提高ＡＳＰ系统的处理能力,采用分布工 一个方向。微软系统已为我们提供了这样的平台,但在设计分布式ＡＳＰ应用系统时,为了保证能够不断地得到性能提高。本提出一三个设计策略,无状态请求,无状态中间层和使用地数据缓存对象。     

Windows NT可执行文件的块结构剖析

深入地剖析了ＷｉｎｄｏｗｓＮＴ可执行文件的块表与埠之间的构结关系,探讨了获取系统文件块的方法,揭示了可执行文件重要信息块的结构及运行机制;并结合ＷｉｎｄｏｗｓＮＴ系统程序ＳＥＴＵＰ ＥＸＥ验证了这一分析的正确性。     

二苯醚类原卟啉原氧化酶抑制剂的构效关系研究

通过比较具有抑制原卟啉原氧化酶活性的二苯醚类化合物空间结构上的相似性,确定了该灯化合活性构象和重叠规则。利用比较分子力场分析（ＣoＭＦＡ）方法进行了三维定量构 效关系研究,得到敢具有较高预测能力的ＱＳＡＲ模型;发现二苯醚类化合物两个苯环的才相对取向对其生物活性有重要影响,此研究结果对进一步设计、合成具有高活性的新型抑制剂具有重要的指导意义。     

一类来氟米特类似物二氢乳清酸脱氢酶抑制剂作用模式的理论研究

目的:来氟米特是当今临床上类风湿关节炎疾病治疗中最具有显著病情缓解作用的抗风湿药物之一.本文分析二氢乳清酸脱氢酶(DHODH)与其抑制剂的相互作用模式,以指导新型抗风湿药物的开发.方法:从1D3H晶体结构出发,采用基于配体-受体复合物相互作用的药效团研究方法,建立来氟米特活性代谢物A771726的药效团模型;以晶体中来氟米特活性代谢物A771726为模版,构建42个来氟米特类似物DHODH抑制剂的结构,经结构叠合,采用自组织分子力场分析方法(SOMFA),建立来氟米特活性代谢类似物DHODH抑制剂三维定量构效关系模型;并探讨DHODH与其抑制剂的相互作用模式.结果与结论:建立了合理的来氟米特活性代谢物药效团模型和DHODH抑制剂三维定量构效关系,并且2种方法所得的模型吻合.确定的DHODH与抑制剂的作用模式,可以指导抑制剂的设计,用于开发新型抗风湿药物.     

氰基丙烯酸酯类化合物的3D-QSAR研究

3D-Quantitative Structure—Activity Relationships of a series of cyanoacrylate inhibitors which are known to act by blocking photosynthetic electron transport close to photosystem II reaction center in the thylakoid membranes of plant chloroplasts have been investigated using comparative molecular field analysis(CoMFA). The active conformations of the title compounds were obtained by constrained systematic search program. The resulting CoMFA model with considerable predictive ability shows that the contribution of steric effects for activities of cyanoacrylate inhibitors is more important than electrostatic effects.     

Photochemical reflectance index and leaf photosynthetic radiation-use-efficiency assessment in Mediterranean trees

This Letter presents new data validating the use of the photochemical reflectance index PRI (R570-R531)/(R570 + R531) to assess photosynthetic- radiation-use-efficiency under mild water stress. Gas exchange, fluorescence and the PRI of leaves from the Mediterranean trees Quercus ilex and Phillyrea latifolia growing in the field were followed from spring to summer 1996 in central Catalonia (NE Spain). The same variables were measured in seedlings of these two species and Pistacia lentiscus submitted to progressive drying after witholding irrigation. Except for severely drought damaged plants, significant relations of the reflectance index PRI with fluorescence yield of the photosystem II (Delta F/F' m), non photochemical fluorescence quenching ( qN ) and photosynthetic radiation use efficiency (PRUE) were found, thus indicating a functional relation among these parameters. A simple portable radiometer measuring ground level reflectance at narrow bands centred at 531 and 570nm could instantaneously calculate the PRI index and give the PRUE estimation.     

Prolonged sensitivity of immobilized thylakoid membranes in cross-linked matrix to atrazine

Freshly prepared pea thylakoid membranes were immobilized in bovine serum albumin-glutaraldehyde cross-linked matrix (BSA-GA matrix) and their stability under long term storage was analyzed by Pulse-Amplitude-Modulated (PAM) chlorophyll fluorescence and photosynthetic oxygen evolution measured by oxygen rate electrode. The thylakoid membranes stored at 4 °C showed prolonged stability in BSA-GA matrix and additional adsorption on nitrocellulose membrane filters gave them more stability. The sensitivity of the parameters of the oxygen evolution of thylakoid membranes to atrazine increased with immobilization. The half-inhibition time for oxygen evolution and quantum efficiency of photosynthesis could be prolonged to more than 15 days. These results suggest that the immobilized thylakoid membranes in BSA-GA matrix can be used as biological receptor in biosensors for a long period of time (up to 25 days) applying the proposed new method for atrazine detection by using polarographic oxygen rate electrode. This method is more sensitive, faster and easier to use than other methods for detection of herbicides based on determination of the photochemical activity of photosystem II.     

Leaf level detection of solar induced chlorophyll fluorescence by means of a subnanometer resolution spectroradiometer

A leaf level investigation on the spectral signature of Phaseolus vulgaris was undertaken by using a very high spectral resolution spectroradiometer featuring full width at half maximum of 0.06 nm and spectral range of 635.5-802.5 nm. High spectral resolution allows detection of leaf reflected and emitted radiance fields in two narrow absorption bands at 687 and 760 nm, respectively, where solar irradiance is strongly reduced owing to molecular oxygen absorption of the terrestrial atmosphere. The flux emitted due to chlorophyll fluorescence was measured using the Fraunhofer line depth principle by spectrally modelling the signal, capitalizing on the high resolution of the spectroradiometer devices. An experiment was conducted on two potted bean plants. One was maintained in good health for use as a reference while the other was treated with a photosystem II inhibitor. Collected spectra show that the fluorescence emission produces a pair of characteristic peaks superimposed on the typical leaf-specific reflectance curve. The magnitude of the fluorescence signal of the herbicide-treated leaf was four times greater than that of the control plant, thus indicating damage to the photosynthetic apparatus of the plant.     

光系统II抑制剂的三维构效关系和相关性研究

光系统II(PSII)抑制剂要导致PSII反应中心的电子传递受阻，被认为是重要的除草剂。近年来发现许多化合物都有希尔反应抑制活性。本文利用比较分子场分析方法，在药效团模型基础上，对不同系列的光系统II抑制剂的结构和活性关系进行了分析和讨论。     

Estimating photosynthetic light‐use efficiency using the photochemical reflectance index: the effects of short‐term exposure to elevated CO2 and low temperature

There is growing interest in using the photochemical reflectance index (PRI) to estimate photosynthetic light‐use efficiency (LUE) in studies of terrestrial carbon exchange. However, evidence suggests that the PRI is correlated with LUE only while there is coordinated adjustment between PSII (photosystem II) photochemical efficiency (ΔF/F_m′) and the CO₂ fixation rate. The range of environmental conditions under which this occurs has yet to be fully explored. In this study we examined for 13 species the response of ΔF/F_m′, LUE, and the PRI to short‐term exposure to elevated CO₂ and low temperature. The PRI was linearly correlated with both ΔF/F_m′ and LUE under all conditions. Under elevated CO₂, LUE was considerably enhanced without significantly affecting either ΔF/F_m′ or the PRI. This is consistent with current mechanistic understanding of the basis of the PRI/LUE relationship. In contrast, ΔF/F_m′, LUE, and the PRI were on average reduced proportionally by low temperature. This suggests simple multiplicative scaling may be sufficient to account across species for the effect of typical diurnal temperature variations in PRI/LUE relationships.     

Simple reflectance indices track heat and water stress-induced changes in steady-state chlorophyll fluorescence at the canopy scale

Non-invasive remote sensing techniques for monitoring plant stress and photosynthetic status have received much attention. The majority of published vegetation indices are not sensitive to rapid changes in plant photosynthetic status brought on by common environmental stressors such as diurnal fluxes in irradiance and heat. This is due to the fact that most vegetation indices have no direct link to photosynthetic functioning beyond their sensitivity to canopy structure and pigment concentration changes. In contrast, this study makes progress on a more direct link between passive reflectance measurements and plant physiological status through an understanding of photochemical quenching (qP) and non-photochemical quenching processes. This is accomplished through the characterization of steady-state fluorescence (Fs) and its influence on apparent reflectance in the red-edge spectral region. A series of experiments were conducted under controlled environmental conditions, linking passive reflectance measurements of a grapevine canopy (Vitis vinifera L. cv. Cabernet Sauvignon) to leaf level estimates of CO₂ assimilation (A), stomatal conductance (g), qP, and Fs. Plant stress was induced by imposing a diurnal heat stress and recovery event and by withholding water from the plant canopy over the course of the experiment. We outlined evidence for a link between Fs and photosynthetic status, identified the Fs signal in passive remote sensing reflectance data, and related reflectance-derived estimates of Fs to plant photosynthetic status. These results provide evidence that simple reflectance indices calculated in the red-edge spectral region can track temperature and water-induced changes in Fs and, consequently, provide a rapid assessment of plant stress that is directly linked to plant physiological processes.     

Time-resolved absorption as optical method for herbicide detection

A new sensing system for the detection of photosynthetic herbicides in water has been developed, based on the use of a trans-membrane protein complex, the reaction centre (RC) isolated from Rhodobacter sphaeroides. The stationary and excited state of this protein are characterised by different absorption properties. The path followed by the protein to return to the stationary state is influenced by the presence of photosynthetic herbicides. Therefore the concentration of herbicides could be measured by monitoring the temporal changes of absorption following optical excitation. For this purpose, an optoelectronic system has been realised. It makes use of a 860 nm light emitting diode and a hybrid photodetector and is coupled to a 5 cm-long optical cell containing the RC solution through optical fibres. The system was tested with atrazine and a limit of detection of 10 nM was obtained.     

水肥(氮)对小麦生理生态的影响(Ⅰ)水肥(氮)条件对小麦光合蒸腾与水分利用的影响

光合速率在日出后随着光强的增强而急速升高,4月20日是小麦光合最强。净光合速率日变化随施氮量的增加而下降,水胁迫处理显著低于高水处理;不同时段变化净光合速率随施氮量和土壤含水量的增加而增加,但总的趋势是降低的。小麦蒸腾速率日变化总体趋势是在日出后随着光强的增强而急速升高、随光强的减弱而降低。小麦蒸腾速率日变化曲线为单峰型,中午最高。叶片蒸腾速率日变化随土壤水分供应增加而增加,随氮肥供应增加而下降;不同供水供氮条件下,叶片蒸腾速率的分异在日中尤其是上午比较明显。蒸腾速率从4月10日一直呈现下降趋势。小麦叶片水分利用率日变化曲线为"L"型,即早上较高,中午和下午都非常低。4月20日叶片水分利用率最高,5月10日最低。叶片对不同土壤水分和氮控制的反映为高氮低水高水分利用率,反之,则水分利用率较低。不同水、氮在上午对叶片水分利用率影响差异比较明显,下午则趋于一致。     

Data analysis pipeline from laboratory to MP models

A workflow for data analysis is introduced to synthesize flux regulation maps of a Metabolic P system from time series of data observed in laboratory. The procedure is successfully tested on a significant case study, the photosynthetic phenomenon called NPQ, which determines plant accommodation to environmental light. A previously introduced MP model of such a photosynthetic process has been improved, by providing an MP system with a simpler regulative network that reproduces the observed behaviors of the natural system. Two regression techniques were employed to find out the regulation maps, and interesting experimental results came out in the context of their residual analysis for model validation.