Gene cloning, expression, and biochemical characterization of a recombinant trehalose synthase from Picrophilus torridus in Escherichia coli

A trehalose synthase (TSase) gene from a hyperacidophilic, thermophilic archaea, Picrophilus torridus, was synthesized using overlap extension PCR and transformed into Escherichia coli for expression. The purified recombinant P. torridus TSase (PTTS) showed an optimum pH and temperature of 6.0 and 45 degrees C, respectively, and the enzyme maintained high activity at pH 5.0 and 60 degrees C. Kinetic analysis showed that the enzyme has a 2.5-fold higher catalytic efficiency (k(cat)/K(M)) for maltose than for trehalose, indicating maltose as the preferred substrate. The maximum conversion rate of maltose into trehalose by the enzyme was independent of the substrate concentration, tended to increase at lower temperatures, and reached approximately 71% at 20 degrees C. Enzyme activity was inhibited by Hg2+, Al3+, and SDS. Five amino acid residues that are important for alpha-amylase family enzyme catalysis were shown to be conserved in PTTS (Asp203, Glu245, Asp311, His106, and His310) and required for its activity, suggesting this enzyme might employ a similar hydrolysis mechanism.     

Baicalein induction of hydroxyl radical formation via 12-lipoxygenase in human platelets: an ESR study

The pro-oxidant activities of baicalein, morin, myricetin, quercetin, and rutin were examined in various cell-containing systems including human platelets, rat vascular smooth muscle cells, human umbilical vein endothelial cells (HUVECs), human THP-1 cells, and fibroblast cells. Electron spin resonance (ESR) results showed that only baicalein generated hydroxyl radicals in a resting human platelet suspension, whereas the other flavonoids showed no effects on any of the resting cell systems. A low concentration of arachidonic acid (AA) increased the intensity of hydroxyl radicals, but a high concentration inhibited it. Collagen and thrombin, platelet aggregatory agents that can cause the release of AA by platelets, enhanced baicalein-induced hydroxyl radical formation, whereas ADP and U44619 showed no significant effects. Quinacrine and 5,8,11,14-eicosatetraenoic trifluoromethyl ketone, both PLA2 inhibitors, significantly attenuated baicalein-induced hydroxyl radical formation. These results suggest that baicalein-induced hydroxyl radical formation is associated with AA metabolite enzymes in human platelets. The formation of hydroxyl radicals was significantly inhibited by lipoxygenase inhibitors including nordihydroguaiaretic acid, (-)-epicatechin, (-)-epicatechin gallate, and hinokitiol, but was not affected by desferroxamine or the heme protein inhibitors KCN and NaN3. On the other hand, semiquinone free radicals were generated when baicalein was incubated with horseradish peroxidase/H2O2 or platelets/AA. The semiquinone radicals formed in the platelets/AA system could be extensively inhibited by desferroxamine, diethylenetriaminepentaacetic acid, KCN, and NaN3, indicating that prostaglandin H synthase (PGHS)-peroxidase may be involved. The results of this study led to the proposal that baicalein induces hydroxyl radical formation via 12-lipoxygenase and induces semiquinone radical formation via PGHS-peroxidase in human platelets.     

生活垃圾微生物强化堆肥对放线菌群落的影响

为了探讨微生物强化堆肥对生活垃圾好氧堆肥过程及堆肥过程中放线菌群落的影响,在堆肥过程中接种高效细菌复合菌剂和真菌复合菌剂,并以不接种的堆体为对照,对堆肥过程的温度变化和木质纤维素的降解效率进行了测定,并借助于PCR-DGGE方法对堆肥过程中放线菌群落的动态变化和种群多样性进行研究。结果表明：微生物强化堆肥能缩短堆体起爆时间,并能有效提高堆体降温期和二次发酵期的温度;和自然堆肥相比微生物强化堆肥使半纤维素、纤维素和木质素的降解率分别提高8.95%、12.72%和10.13%。DGGE图谱显示：2种堆肥方式的放线菌多样性指数表现出极显著差异,微生物强化堆肥能增加堆体中优势菌群的种类和数量,能有效提高腐熟期的放线菌群落多样性,有利于堆肥腐熟。优势条带测序结果表明：在接种堆肥过程中检测到了放线菌门的棒杆菌属、分支杆菌属、链霉菌属、热孢菌属、迪茨菌属、糖丝菌属和放线菌属。     

罗汉果种子传播小西葫芦黄化花叶病毒的检测

为了解小西葫芦黄化花叶病毒（Zucchini yellow mosaicvirus,ZYMV）是否能通过罗汉果种子传播。本研究通过取ZYMV阳性的罹病罗汉果植株种子700粒,400粒直接播种于防虫网室中,300粒经表面消毒处理后播种于MS培养基上。最终获得213棵罗汉果实生苗。对所获得实生苗进行生物学鉴定及ZYMV特异性RT-PCR检测,均未检测到ZYMV阳性植株。结果表明ZYMV不能经罗汉果种子传播,或其传播率很低。     

A rapid spectrofluorometric screening method for enrofloxacin in chicken muscle

A simple spectrofluorometric method was developed for screening enrofloxacin (ENRO) in chicken muscle. A single-step extraction with acidic acetonitrile gave the best results without further cleanup. Following centrifugation the supernatants were excited at 324 nm and the emission was measured at 442 nm. Using this procedure, 18 chicken breast samples from 3 producers were tested. The results showed background signal levels significantly lower than those corresponding to 300 microg/kg ENRO, the FDA approved tolerance level. Statistical treatment of these data established a threshold which can be used in subsequent screening of ENRO at the tolerance level. The calibration curve revealed a satisfactory linear relationship (R(2) = 0.9991) in a range of 0-700 microg/kg ENRO in fortified chicken breast. ENRO-incurred samples were examined using this approach, and the results agreed with those obtained from more extensive separation followed by high-performance liquid chromatography. Because the threshold can be set at the 3 sigma limit, reliable screening can be accomplished with an error rate of less than 0.26%. Based on this investigation, a high-throughput screening method for ENRO in chicken tissue is proposed.     

利用叶片光谱的作物铜铅污染判别

重金属污染种类的判别是作物生长环境监测的重要组成部分.该研究旨在提出一种由叶片光谱构建的铜铅污染判别特征(Copper and Lead Contamination Discriminating Features,CLCDF),以实现作物铜、铅污染判别.以典型作物玉米为试验对象,运用包络线去除与导数处理叶片光谱,基于该...     

基于网络RTK的离心式无人机变量施药可行性初探

针对植保无人机施药准确性和作业效率需求的提高,验证网络实时动态(Real-Time Kinematic,RTK)载波差分技术在无人机施药上的可行性,设计了一种基于网络RTK的离心式变量施药系统.采用STM32F103为控制核心,通过串口获取GPS定位信息,并连接DTU模块实现网络RTK技术,通过脉冲宽度调制(Pulse...     

白果活性蛋白的酶法水解及抗氧化活性研究

白果活性蛋白(GAP)是华中农业大学天然产物化学实验室首次从白果中分离得到的一种以清蛋白为主的且具有显著生物活性的蛋白,为扩大该蛋白在食品中的用途,提高其生物活性,研究了酶法水解制备白果肽段的方法及其抗氧化活性的变化。通过单因素分析、正交试验以及对试验结果的分析,确定了2709碱性蛋白酶水解白果活性蛋白的最佳水解条件为：底物浓度1%,pH值8.5,水解温度45℃,酶浓度7000 U/g,反应时间6 h。以Fenton体系和邻苯三酚体系检验其抗氧化活性,结果表明白果肽段较酶解前的活性蛋白,抗氧化活性有不同程度的提高,但两者均具有较强的抗氧化活性。     

固定道保护性耕作节能效果试验研究

固定道保护性耕作限制了机具对土壤的普遍性压实，提高了拖拉机牵引性能，降低了能耗。在北京郊区青云店镇试验区，设置固定道及非固定道保护性耕作对照区。通过播种机开沟器阻力正交试验及牵引阻力测试试验，研究固定道保护性耕作对播种、深松作业的牵引力及油耗的影响。试验表明：在0．05的置信水平下，对比作业速度、深度租土壤坚实度因素，土壤坚实度因素因田间分布均匀性较低，对开沟阻力波动影响最为显著；非固定道保护性耕作因轮胎压实，破坏了表层土壤均匀性，造成作业负荷变动大，加剧燃油消耗；相对于非固定道保护性耕作，按华北小麦-玉米一年两熟地区两年一深松模式估算，固定道保护性耕作仅播种、深松两项作业一年每公顷节省15．7L柴油；固定道保护性耕作因减少了压实面积，从而可以提高拖拉机田间作业的牵引性能，减小机具的作业阻力，降低燃油消耗，达到减少压实、节约能耗的作用。     

基于GIS和Logistic模型的香榧生态适宜性评价

研究香榧栽培的生态适宜性将为香榧的引种、扩种和区划提供理论依据。该研究在GIS支持下,以地学数据库为基础,以logistic 回归模型为手段,利用高分辨率遥感影像、数字高程模型以及土壤、气象和实地调查等资料对研究区香榧生态适宜性开展精确评价。研究结果表明,香榧栽培高度适宜区和中度适宜区累计占总面积的61.7%,其中高度适宜区面积达183 hm2,占总面积的11.4%,说明研究区香榧栽培发展潜力巨大。该评价结果为当地香榧资源产业化发展提供了科学依据。