Biosensors based on highly sensitive acetylcholinesterases for enhanced carbamate insecticides detection

This paper presents the construction of amperometric biosensors for the highly sensitive detection of carbamate insecticides based on the inhibition of acetylcholinesterase (AChE). This enzyme was immobilised by entrapment in an optimised sol-gel matrix on TCNQ-modified screen-printed electrodes. The enzyme activity was estimated by measuring the thiocholine produced by the enzymatic hydrolysis of the acetylthiocholine using TCNQ as mediator. Wild and genetically engineered AChEs from Drosophila melanogaster (Dm) were chosen for their high sensitivity towards insecticides, which substantially improves the LOD compared with cholinesterases from other sources. The wild type and three mutant enzymes were tested against three carbamate insecticides: carbaryl, carbofuran and pirimicard. The best LOD were obtained with the Y370A mutant for carbaryl (1 × 10⁻⁸ M), the E69W mutant for pirimicarb (2 × 10⁻⁸ M) and the I161V mutant for carbofuran (8 × 10⁻¹⁰ M). The biosensors were applied to the analysis of two potable water samples.     

Monoclonal antibody-based enzyme-linked immunosorbent assay for the insecticide imidacloprid

An enzyme-linked immunosorbent assay (ELISA) was developed for the neonicotinoid insecticide imidacloprid, 1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine using monoclonal antibodies (MAb). Three MAbs, designated as E6A6, E6F3 and H7F7, were raised from mice immunized with an imidacloprid hapten-ovalbumin conjugate. These MAbs performed similarly in indirect competition ELISA (icELISA), so one, E6F3, was selected for detailed study. The equilibrium constants (K_d) and association and dissociation rate constants (k_on, k_off) for five neonicotinoids and one imidacloprid metabolite to E6F3 were determined by kinetic exclusion fluoroimmunoassay (KinExA). Affinities (1/K_d) of E6F3 for acetamiprid and clothianidin were similar, but 50-fold weaker than that of imidacloprid. MAb E6F3 had no measurable affinity for the other neonicotinoids. The icELISA can tolerate up to 15% (v/v) acetone or 20% (v/v) methanol. Assay sensitivity was similar at pH 4-9, 1-10-fold concentration of PBS with or without 0.05% Tween 20, and incubation times of 30-180 min. The half-maximal inhibition and the limit of detection were approximately 0.8 and 0.1 μg/l of imidacloprid in icELISA, and 0.3 and 0.03 μg/l in direct competition ELISA (dcELISA), respectively. Analysis of imidacloprid-fortified water and cucumber samples by the icELISA showed average recoveries from 70 to 120%.     

MICROWAVE SYNTHESIS OF TRICHLORFON AND ITS ANALOGUES

The synthesis of dialkyl-(2,2,2-trichloro-1-Hydroxyethyl) phosphonates using dialkyl hydrogen phosphite and chloral hydrate under solvent-free condition by microwave irradiation is reported. The products were chrachetrized using ¹ H NMR, ¹³ C NMR, and ³¹ P NMR spectroscopy.     

Phenylboronic acid-functionalized cross-linked chitosan magnetic adsorbents for the magnetic solid-phase extraction of benzoylurea pesticides

In this study, a 4-formylphenylboronic acid-modified cross-linked chitosan magnetic nanoparticle (FPBA@CCHS@Fe₃O₄) was fabricated. The synthesized material was utilized as the magnetic solid-phase extraction adsorbent for the enrichment of six benzoylurea pesticides. In addition to B-N coordination, FPBA@CCHS@Fe₃O₄ interacts with benzoylureas through hydrogen bonds and π-π stacking interaction on account of rich active groups (amino and hydroxyl) and aromatic rings in structure. Compared to traditional extraction methods, less adsorbent (20 mg) and reduced extraction time (3 min) were achieved. The adsorbent also exhibited good reusability (no less than 10 times). Coupled with a high-performance liquid chromatography–diode array detector, satisfactory recoveries (89.1–103.9%) and an acceptable limit of detection (0.2–0.7 μg/L) were obtained. Under optimized conditions, the established method was successfully applied to the tea infusion samples from six major tea categories with acceptable recoveries ranging from 76.8 to 110%, indicating its application potential for the quantitative detection of pesticides in complex matrices.     

煤基腐植酸对久效磷的增效作用研究

水溶性煤基酸分为从含有水溶性煤基酸的低价煤中抽提得到的水溶性煤基酸和从不含有水溶性煤基酸的低阶煤中氧化得到的水溶性煤基酸。考察了从武川风化煤和霍林河风化褐煤通过两步催化氧化法得到的水溶性煤基酸和从晋城风化煤中得到的水溶性煤基酸对高效、高毒性的杀虫剂--久效磷生物活性的影响。结果表明：（1）三种煤基酸都能增加久效磷的生物活性；（2）所用水溶性煤基酸的理想浓度为0.0025％；（3）根据毒力曲线，久效磷、武川煤基酸-久效磷和霍林河-久效磷的致死中浓度为9.94g/ha，5.99g/ha，6.62g/ha，相对毒力系数分别为：100，165.9，150.2；（4）大田实验结果证实了水溶性煤基酸对久效磷的增效作用。     

Study on the photodegradation and microbiological degradation of pirimicarb insecticide by using liquid chromatography coupled with ion-trap mass spectrometry

The intermediates of photodegradation and microbial degradation of pirimicarb insecticide were investigated by liquid chromatography coupled with ion-trap mass spectrometry (LC–IT-MS). Different intermediates were detected in the photodegradation and microbial degradation of pirimicarb. In the photodegradation of pirimicarb in aqueous solution 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167), 2-methylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 224) and 2-formylamino-5,6-dimethylpyrimidin-4-yl-dimethylcarbamate (MW = 252) were the main products. It was found that 2-dimethylamino-5,6-dimethyl-4-hydroxypyrimidine (MW = 167) was the major product in the microbial degradation of pirimicarb in soil.     

新烟碱类杀虫剂生物活性的理论研究和结构修饰*

在B3LYP/6-311G基组水平下,运用密度泛函理论(DFT)的量子化学方法,对20种重氮乙烷新烟碱类杀虫剂分子的电子结构特征进行了研究,获得了它们的前线轨道能(EHOMO、ENHOMO、ELUMO、ENLUMO等)、原子电荷(Qi)、摩尔熵(Sm)、偶极矩(μ)等量化参数与物理性质。经最佳变量子集回归研究发现,重氮乙烷新烟碱类杀虫剂分子对果蝇n AChRs、哺乳动物α4β2亚型的亲和力常数(p KD、p KA)分别与ELUMO、QW、QF、QN等参数具有良好的线性关系。逐一或逐四剔除交互验证以及VIF、tα/2检验,所建2个QSAR模型具有良好的稳健性及预测能力。根据2个QSAR模型推断了重氮乙烷新烟碱类分子可能的杀虫机理。进一步研究发现,在重氮乙烷新烟碱类分子的吡啶环上的合适部位,选用不含复键的吸电子能力较强的取代基团对其进行结构修饰,有利于提高修饰后分子的生物活性。基于分子17,设计出4种经结构修饰后对果蝇n AChRs亲和力显著提高的重氮乙烷新烟碱类分子(分别是分子27,28,30和31),希望能得到实验的证实。     

有机磷杀虫剂胺丙畏的红外光谱研究

本文采用红外光谱仪对有机磷杀虫剂胺丙畏进行研究,通过其红外光谱信息,对谱峰进行归属,并鉴定出胺丙畏中的Z,E-异构体。     

An optical resolution of racemic organophosphorous esters by phosphotriesterase-catalyzing hydrolysis

Conclusion  We have shown that PTE chiral recognition is limited to organophosphorous esters having the chiral center on the phosphorous atoms, which is attacked with nucleophile, not having the chiral center on the other atoms of the leaving group. Therefore, PTE can be utilized for the synthesis of their chiral organophosphorous esters.