Fluorescence polarization immunoassay based on a monoclonal antibody for the detection of the organophosphorus pesticide parathion-methyl

A fluorescence polarization immunoassay (FPIA) based on a monoclonal antibody for the detection of parathion-methyl (PM) was developed and optimized. Fluorescein-labeled PM derivatives (tracers) with different structures were synthesized and purified by thin-layer chromatography. The influence of immunogen and tracer structures on the assay characteristics was investigated. PM concentration determinable by the FPIA ranged from 25 to 10000 ppb. The detection limit was 15 ppb. Methanol extracts of vegetable, fruit, and soil samples were diluted 1/10 for the analysis. Recovery in spiked samples averaged between 85 and 110%. The method developed is characterized by high specificity and reproducibility (CV ranged from 1.5 to 9.1% for interassay and from 1.8 to 14.1% for intra-assay). The FPIA method can be applied to the screening of food and environmental samples for PM residues without complicated cleanup.     

Levan fructotransferase from Arthrobacter oxydans J17-21 catalyzes the formation of the di-D-fructose dianhydride IV from levan

A new levan fructotransferase (LFTase) isolated from Arthrobacter oxydans J17-21 was characterized for the production of difructose dianhydride IV (DFA IV). LFTase was purified to apparent homogeneity by Q-Sepharose ion exchange chromatography, Mono-Q HR 5/5 column chromatography, and gel permeation chromatography. The enzyme had an apparent molecular mass of 54000 Da. The optimum pH for the enzyme-catalyzed reaction was pH 6.5, and the optimum temperature was observed at 45 degrees C. The LFTase was activated by the presence of CaCl(2) and EDTA-2Na but inhibited strongly by MnCl(2) and CuSO(4) at 1 mM and completely by FeSO(4) and Ag(2)SO(4) at 1 mM. A bacterial levan from Zymomonas mobilis was incubated with an LFTase; final conversion yield from the levan to DFA IV was 35%. Neither inulin, levanbiose, sucrose, dextran, nor starch was hydrolyzed by LFTase. DFA IV was very stable at acidic pH and high temperature, thus indicating that DFA IV may be suitable for the food industry and related areas.     

Levels of active oxygen species are controlled by ascorbic acid and anthocyanin in Arabidopsis

Stabilization of the levels of active oxygen species (AOS) is important to the survival of organisms. To clarify the system controlling levels of AOS in plants, this study used an electron spin resonance (ESR) method to directly measure superoxide radical (O(2)(.-)) scavenging activities in the wild-type Arabidopsis thaliana (Col and Ler ecotypes), two anthocyanin mutants (tt3 and ttg1), and an ascorbic acid mutant (vtc1). Under ordinary growth conditions, Arabidopsis contained superoxide-scavenging activity (SOSA) of approximately 300-500 SOD units/g of fresh weight. The ESR pattern indicated that most (40-50%) of this activity was due to ascorbic acid. For the analysis of SOSA under conditions of oxidative stress, synthesis of AOS was induced by gamma-irradiation. The radical scavenging activity in irradiated plants increased approximately 10-fold following an associated increase in the accumulation of ascorbic acid and anthocyanin. The accumulation of ascorbic acid and anthocyanin was suppressed by treatment with an antioxidant before irradiation and was induced by treatment with a radical-generating reagent. The contributions of ascorbic acid and anthocyanin to the total superoxide radical scavenging activity differed among ecotypes. In the Ler ecotype, ascorbic acid accumulated at twice the level of that in the Col ecotype, and induction of anthocyanin was half that in Col. To confirm the activity of ascorbic acid and anthocyanin against AOS stress, the viability of the wild type and mutants (tt2, tt3,tt5, ttg1, and vtc1) was examined after gamma-irradiation. Only the plants in which ascorbic acid and anthocyanin were induced had the ability to grow and flower.     

Contribution of individual polyphenolics to total antioxidant capacity of plums

To study the effect of polyphenolics on antioxidant capacities of plums, the amounts of total phenolics, total flavonoids and individual phenolic compounds, and vitamin C equivalent antioxidant capacity (VCEAC) of eleven plum cultivars was determined. There was a good linear relationship between the amount of total phenolics and total antioxidant capacity (r2 = 0.9887). The amount of total flavonoids and total antioxidant capacity also showed a good correlation (r2 = 0.9653). Although the summation of individual antioxidant capacity was lower than the total antioxidant capacity of plum samples, there was a positive correlation (r2 = 0.9299) of total antioxidant capacity of plum samples with the sum of the VCEACs calculated from individual phenolics. Chlorogenic acids and glycosides of cyanidin, peonidin, and quercetin were major phenolics among eleven plum cultivars. The antioxidant capacity of chlorogenic acids and anthocyanins showed higher correlation (r2) of 0.7751 and 0.6616 to total VCEAC, respectively, than that of quercetin glycosides (r2 = 0.0279). Chlorogenic acids were a major source of antioxidant activity in plums, and the consumption of one serving (100 g) of plums can provide antioxidants equivalent to 144.4-889.6 mg of vitamin C.     

Synthesis of conjugated linoleic acid by human-derived Bifidobacterium breve LMC 017: utilization as a functional starter culture for milk fermentation

This study was performed to discover bifidobacteria isolated from human intestines that optimally convert linoleic acid (LA) to conjugated linoleic acid (CLA) and to optimize the culture conditions of milk fermentation. One hundred and fifty neonatal bifidobacteria were screened for CLA-producing ability, and Bifidobacterium breve LMC 017 was selected as it showed about 90% conversion of free LA in MRS broth. The selected strain showed resistance at 0.5% LA in microaerophillic conditions. When monolinolein (LA 90%) was used as a substrate for CLA production, the conversion rate was lower compared to free LA, but the growth rate was unaffected during the milk fermentation. There was no significant difference in CLA production between aerobic and anaerobic conditions, and little decline in CLA was shown after the maximal CLA level had been reached. CLA production increased by 80% with 24 h of incubation in milk containing additional skim milk (5%), where the proteins may have facilitated the production of CLA by enhancing the interaction of substrate with the bacteria. CLA production did not decline after 9 h of fermentation and an additional 12 weeks of storage with other commercial starters. This demonstrates the possibility of using this strain as a costarter in the production of CLA-enriched yogurt.     

坡耕地地表糙度对降水分配的实验研究

地表糙度指地表微小的高低起伏变化,是人为土地管理与土壤侵蚀共同作用的结果,可以影响降雨过程中水分转化与土壤侵蚀过程。该文以直线坡为对照,借助3种常见耕作管理措施（人工锄耕、人工掏挖与等高耕作）产生不同水平的地表糙度,结合人工模拟降雨试验研究地表糙度水分转化效应。结果表明:长历时人工降雨条件下,地表糙度可以强化降雨向土壤水分转化。其强化入渗作用表现为:增加地表填洼量,增大入渗水头与入渗深度,滞后产流时间,削减径流量,进而提高入渗率及水分转化率。坡耕地地表糙度与填洼量成指数关系,与平均入渗率及水分转化率成对数关系。     

经济作物替代薯稻三熟制早稻对肥料利用、土壤养分和经济效益的影响

为缩短"薯-稻-稻"三熟制作物早稻的生育期,促进"薯-稻-稻"茬口顺畅衔接,提高整体经济效益,本研究以不同经济作物替代早稻,分别在2016年惠东县和2017年白云区试点进行田间试验,共设置5个处理:休耕T₀(空白对照,不种任何作物)、常规处理T_CK(早稻)、T₁(黄瓜)、T₂(豆角)、T₃(甜玉米),探究不同春播经济作物生育期、产量、种植效益和肥料效率及土壤酶活的差异。结果表明,种植黄瓜、豆角和甜玉米替代早稻均可明显增加经济效益和缩短生育期。其中,T₃效果最优,与T_CK相比,单位面积种植效益增加了1.32～3.72元·m^-2,生育期缩短了37～43 d,收获指数提高了18.6%～20.1%;同时,增加了土壤有效磷和速效钾含量,增强了土壤脲酶、磷酸酶和过氧化氢酶的活性。综上,甜玉米等经济作物代替早稻形成的"经济作物-中晚稻-冬种马铃薯"三熟轮作模式可以使作物茬口衔接更加顺畅,提升三季作物的整体经济效益,对农民增收具...     

煤矿复垦区不同有机物料的分解特征

  【目的】  研究不同有机物料在矿区复垦土壤中的分解速率及养分释放特征,为合理利用有机资源培肥矿区复垦土壤提供科学依据。  【方法】  在山西黄土丘陵区矿区复垦长期试验点进行大田填埋分解试验。采用尼龙网袋法,将供试的4种有机物料小麦秸秆、玉米秸秆、牛粪和猪粪烘干后过2 mm筛,均按等有机碳量 (8 g) 称取后装入尼龙网袋埋入试验地15 cm深。在填埋后的第12、23、55、218、280、365天采样,分析4种有机物料的干物质残留量和氮、磷、钾及半纤维素、纤维素、木质素含量,计算C/N值和木质素(Lignin)/N值。  【结果】  秸秆和粪肥在矿区复垦土壤中的分解速率均在第12天达到最大,然后迅速下降,分解第365天时,小麦秸秆、玉米秸秆、牛粪和猪粪的质量残留率依次为49.8%、55.1%、79.2%和54.0%,有机碳残留率依次为48.8%、53.4%、63.9%和51.8%。供试有机物料的养分释放率存在差异,在最初分解的第23天,玉米秸秆的氮、磷养分出现了明显富集,氮、磷养分残留率分别达到了131.0%和152.7%,小麦秸秆、牛粪和猪粪的氮素残留率依次为93.0%、81.3%和67.8%,磷素的残留率依次为92.5%、98.8%和84.3%,分解第365天时,小麦秸秆中养分释放速率大小表现为钾 > 磷 > 氮,其他3个物料中养分释放速率大小均表现为钾 > 氮 > 磷。从整个分解过程来看,玉米秸秆中氮素和磷素在矿区复垦土壤中表现出先富集再释放的模式,其他3个物料中氮素和磷素均表现为直接释放模式。采用地积温方程能较好地拟合有机物料的分解过程,由方程可知,秸秆和粪肥的分解速率常数 (K) 大小顺序为猪粪 > 小麦秸秆 > 玉米秸秆 > 牛粪。有机物料的分解速率与养分和木质素等成分的含量相关,全磷、半纤维素含量越高分解越快,木质素含量、C/N和Lignin/N越高分解越慢。  【结论】  秸秆和粪肥在山西矿区复垦土壤中的分解速率在填埋后第12天达到最大值,之后分解速率减缓。与秸秆相比,粪肥的有机碳残留率较高,氮、磷养分释放快,其中以牛粪的分解速率最慢,有机碳残留率最高,因此,牛粪可作为矿区复垦土壤培肥的首选有机物料。     

通过转化脂肪酸去饱和酶基因AcoFAD2提高菠萝植株的抗寒能力

为培育抗寒菠萝新品种,本研究通过比较菠萝脂肪酸去饱和酶基因序列和拟南芥脂肪酸去饱和酶基因序列,筛选获得目标基因AcoFAD2;通过农杆菌转化菠萝'台农17'获得过表达AcoFAD2转基因植株TN17FAD2-3;转基因植株和对照在低温条件下进行培养,鉴定转基因植株和对照的不饱和脂肪酸含量及抗寒能力.结果 发现组培苗在7...     

草坪草信息微机管理系统的建立

收集整理了当前国内外可作为草坪草的 987个品种的资料 ,在微机上建立了较为完善的数据库 ,使用者可根据需要任意调用记录。在此基础上 ,设计了一个草坪草品种信息管理系统。通过本系统 ,使用者可对该数据库进行各种操作 ,实现微机贮存和快速查询、更正、添加记录的功能。