靶标酶在除草剂研究与开发中的作用

大多数除草剂都是通过特殊酶的抑制而产生杀草作用的。根据作用靶标对除草剂进行分类,了解靶标酶的作用机理及特性,对于新型除草剂的设计和杂草抗性的防治能够起到很大的帮助。本文介绍了谷胱甘肽转移酶(GST)、细胞色素P450酶、乙酰乳酸合成酶(ALS)、乙酞辅酶A羧化酶(ACCace)的研究进展。并分别从酶的生理功能、酶学特征、抑制剂作用机理、抑制剂的研究、抗性等方面进行了不同程度的阐述。     

基于量化反应性指数的氨基甲酸酯类农药定量构效关系研究

氨基甲酸酯类农药被广泛用于农业生产中,其作用机理主要是通过与乙酰胆碱酯酶共价结合,从而抑制其正常的生物活性,但此类农药的无节制使用导致其大量残留于生态环境中,对整个生态系统的生存安全造成了严重威胁.本文作者基于量化反应性指数,采用遗传/偏最小二乘法,对氨基甲酸酯与其对乙酰胆碱酯酶的抑制活性进行了定量构效关系研究.结果表...     

麦穗鱼脑AChE间接非竞争ELISA定量分析法的建立

用PEG2000双水相萃取、 DEAE-Sephadex A-50和Sephadex G-200方法分离纯化麦穗鱼Pseudorasbora parva脑中的乙酰胆碱酯酶(AChE), 并制备了兔抗麦穗鱼脑AChE抗血清。用兔抗麦穗鱼脑AChE抗体连接抗原, 建立了定量分析麦穗鱼脑AChE的间接非竞争酶联免疫吸附法(Indirect and non-competitive ELISA), 此法操作简便、灵敏度高, 适用于定量检测。该方法的建立有利于AChE在环境科学和农药学研究领域的进一步研究和应用。     

不同防治田内不同发育期拟环纹豹蛛乙酰胆碱酯酶及羧酸酯酶的活性比较

利用紫外分光光度法研究了生物防治田和化学防治田内不同发育期拟环纹豹蛛Pardosa pseudoannulata乙酰胆碱酯酶(AChE)和羧酸酯酶(CarE)的活性特征。结果表明,化防田拟环纹豹蛛各发育时期AChE活性均较生防田中的低,其各发育期AChE的Km值也均明显高于生防田种群。从整个发育期来看,幼体的AChE活性最高,卵囊的最低,说明不同发育阶段AChE活性存在较大差异。而CarE的活性正相反,化防田种群卵囊、幼蛛、雌成蛛和雄成蛛的CarE活性均高于相应生防田种群,且幼蛛的CarE活性高于相应成蛛,生防田种群每一发育阶段CarE的Km值也均高于相应的化防田种群。表明化防田中的拟环纹豹蛛有可能对部分农药产生了一定程度的抗药性。     

梭梭保护酶活性与土壤微生物量的关系

以准噶尔盆地南缘梭梭(Haloxylon ammodendron)为研究对象,研究其 CAT,POD 和 SOD 活性变化,分析梭梭生境土壤含水量及土壤微生物多样性变化.结果表明:土壤含水量随着土壤深度增加而逐渐减少;在天然样地、交错带样地、人工样地中,交错带样地细菌和放线菌含量最高,说明该区域内土壤微生物活跃.从人工梭梭到交错带梭梭再到天然梭梭,POD 活性没有显著变化,CAT 和 SOD 活性逐渐降低,说明人工种植的梭梭需要经过一段时间适应该区域干旱环境,并逐渐转化为天然梭梭.通过研究发现,人工种植梭梭对梭梭群落恢复和发展有着积极作用.     

壳寡糖对烟草防御酶活性及同工酶酶谱的影响

以黄苗榆烟草为试材，摩擦接种法接种烟草花叶病毒，比色法测定了几种防御酶活性，研究壳聚糖对烟草-烟草花叶病毒这一互作系统激发产生的一系列抗病生化反应的可能性。试验结果初步表明：壳聚糖处理可导致烟草叶片PO、CAT、PPO、PAL和β-1，3葡聚糖酶活性不同程度地提高。PO同工酶酶谱分析得知喷药后接毒处理可看到7条酶带且谱带色浓，酶活性强，由此初步认为壳寡糖诱导抗病毒机制与提高PO活性及其增多同工酶酶谱的酶带有关；分析SOD、CAT和PPO三种酶似乎与壳寡糖诱导抗病毒机制相关不大或无相关性，单因素的喷药和接毒多可导致几种防御酶活性的提高，尤其是PAL和β-1，3葡聚糖酶活性提高明显，但喷药后接毒的酶活变化及升高幅度似乎与两单因素的加权效应无关。     

壳寡糖对烟草防御酶活性及同工酶酶0谱的影响

以黄苗榆烟草为试材、摩擦接种法接种烟草花叶病毒,比色法测定了几种防御酶活性,研究壳寡糖对烟草-烟草花叶病毒这一互作系统激发产生的一系列抗病生理生化反应的可能性.试验结果初步表明壳寡糖处理可导致烟草叶片PO、CAT、PPO、PAL和β-1.3葡聚糖酶活性不同程度地提高.PO同工酶酶谱分析得知喷药后接毒处理可看到7条酶带且谱带色浓,酶活性强.由此初步认为壳寡糖诱导抗病毒机制与提高PO活性及其增多同工酶酶谱的酶带有关;分析SOD、CAT和PPO三种酶似乎与壳寡糖诱导抗病毒机制相关不大或无相关性;单因素的喷药和接毒多可导致几种防御酶活性的提高,尤其是PAL和β-1.3葡聚糖酶活性提高明显,但喷药后接毒的酶活变化及升高幅度似乎与两单因素的加权效应无关.     

氟虫腈对二化螟生长发育的影响及对解毒酶的诱导效应

研究了氟虫腈对不同虫态二化螟Chilo suppressalis的作用特点、持续毒性及对解毒酶的诱导效应。结果表明:氟虫腈对二化螟幼虫具有很强的毒杀作用,且毒杀作用随幼虫龄期的增长而逐渐减弱;对二化螟蛹的羽化具有较低的抑制作用;对卵孵化无抑制作用。亚致死剂量氟虫腈能引起幼虫持续死亡,降低存活试虫体重增长率和蛹重。用亚致死剂量氟虫腈处理4龄幼虫后,对其体内羧酸酯酶活性具有明显的诱导效应和时间效应,对谷胱甘肽S--转移酶活性的诱导效应仅在药剂处理后3h内较为显著,对多功能氧化酶活性表现出较强的诱导效应,比活力约为对照的1.37倍。     

Cloning of the acetylcholinesterase 1 gene and identification of point mutations putatively associated with carbofuran resistance in Nilaparvata lugens

Molecular mechanisms of carbofuran resistance in the brown planthopper, Nilaparvata lugens Stål, were investigated. A carbofuran-resistant strain (CAS) showed approximately 45.5- and 15.1-fold resistance compared with a susceptible strain (SUS) and a non-selected field strain (FM), respectively. Activities of the esterase and mixed-function oxidase were approximately 2.8- and 1.6-fold higher, respectively, in the CAS strain than in the SUS strain, suggesting that these enzymes play a minor role in carbofuran resistance. Interestingly, the insensitivity of acetylcholinesterase (AChE) to carbofuran was approximately 5.5- and 3.7-fold higher in the CAS strain compared to the SUS and FM strains, respectively, indicating that AChE insensitivity is associated with carbofuran resistance. Western blot analysis identified two kinds of AChEs, of which the type-1 AChE (encoded from Nlace1, which is paralogous to the Drosophila AChE gene) was determined to be the major catalytic AChE in N. lugens. The open reading frame of Nlace1 is composed of 1989 bp (approximately 74 kD) and revealed 52.5% and 24.3% amino acid sequence identities to those of Nephotettix cincticeps and Drosophila melanogaster, respectively. Screening of point mutations identified four amino acid substitutions (G119A, F/Y330S, F331H and H332L) in the CAS strain that likely contribute to AChE insensitivity. The frequencies of these mutations were well correlated with resistance levels, confirming that they are associated with reduced sensitivity to carbofuran in N. lugens. These point mutations can be useful as genetic markers for monitoring resistance levels in field populations of N. lugens.     

Sites of Action of Noncompetitive GABA Antagonists in Houseflies and Rats: Three-Dimensional QSAR Analysis

Quantitative structure–activity relationships for insecticidal activity (against houseflies) and competitive activity against a specific [³⁵S]tert-butylbicyclophosphorothionate binding (to rat brain membranes) of some picrotoxinin-type 4-aminobutyric acid antagonists, including γ-BHC, endosulfan, bicyclophosphates, dioxatricyclododecenes and related compounds, were examined three-dimensionally using comparative molecular field analysis (CoMFA). The antagonists were classified into two series according to their molecular shapes: i.e. whether their structure was ‘linearly’ extended beyond the ‘mast-head’ position of the ‘boat-like’ skeletons (series 1) or not (series 2). The CoMFA showed that the slopes in steric and electrostatic fields around the molecule were significant for both series in governing the potency variations in insecticidal and binding activities. Hydrophobicity, a possible factor controlling transport behaviour of compounds, was significant in governing variations in insecticidal activity, but not for the case of the rat membrane binding. Assuming that there is a slight topological difference between series 1 and 2 compounds in terms of the mode of binding with the housefly receptor site, the insecticidal activity was analysable with a single equation for the combined set of compounds, but the rat membrane binding was not. The sterically and electrostatically favourable regions surrounding the molecular series indicated by CoMFA were roughly located at positions so as to interact with the binding subsites on the receptors proposed previously. © of SCI.     

Specificity of Rhizobia Nodulating Genista monspessulana and Genista linifolia In Vitro and in Field Situations

Genista monspessulana and Genista linifolia are woody legumes with a high potential value for the rehabilitation of degraded soils , although field establishment of the plantlets in nonnative soils is very difficult because of the lack of specific rhizobial strains . In this work the rhizobia that nodulate the two species were tenta tively classified as a Bradyrhizobium sp . Only those soils with naturally occurring G. monspessulana or G. linifolia, now or in the past , had specific bradyrhizobia . Out of the six rhizobial strains analyzed , only Bradyrhizobium sp . ISLU21 , iso lated from Lupinus luteus, nodulated with the species studied . Out of the 11 legumes inoculated with the strains isolated from G. monspessulana and G. linifolia, only L. luteus produced infective nodules . In a field experiment , plants inocu lated with the specific bradyrhizobia isolates showed higher survival , growth rates , and N content than the noninoculated controls .     

内蒙古大青山油松、虎榛子根际土壤酶活性研究

试验以内蒙古大青山油松(Pinus tabulaeform is)、虎榛子(Ostryopsis davidiana)不同林型根际土壤为材料,进行了土壤酶活性的研究,目的是了解油松与虎榛子不同林型内土壤酶活性的变化规律,最终为内蒙古大青山极度退化生态系统中油松与虎榛子和谐共存机制提供科学依据。试验采用对硝基苯磷酸二钠比色法测定磷酸酶活性,采用3,5-二硝基水杨酸比色法测定蔗糖酶活性,邻苯三酚比色法测定多酚氧化酶活性,苯酚-次氯酸钠比色法测定脲酶活性。酶活性单位均以单位风干土重在培养时间内生成物的量表示。结果表明:油松、虎榛子不同林型内土壤酶活性强弱总排序为:油松、虎榛子混交林(虎榛子纯林(油松纯林。