Action mechanism of the potential biocontrol agent Brevibacillus laterosporus SN19-1 against Xanthomonas oryzae pv. oryzae causing rice bacterial leaf blight.

The causal agent of rice bacterial leaf blight (BLB) is Xanthomonas oryzae pv. oryzae (Xoo), which causes serious damage to rice, leading to yield reduction or even crop failure. Brevibacillus laterosporus SN19-1 is a biocontrol strain obtained by long-term screening in our laboratory, which has a good antagonistic effect on a variety of plant pathogenic bacteria. In this study, we investigated the efficacy and bacterial inhibition of B. laterosporus SN19-1 against BLB to lay the theoretical foundation and research technology for the development of SN19-1 as a biopesticide of BLB. It was found that SN19-1 has the ability to fix nitrogen, detoxify organic phosphorus, and produce cellulase, protease, and siderophores, as well as IAA. In a greenhouse pot experiment, the control efficiency of SN19-1 against BLB was as high as 90.92%. Further investigation of the inhibitory mechanism of SN19-1 on Xoo found that the biofilm formation ability of Xoo was inhibited and the pathogenicity was weakened after the action of SN19-1 sterile supernatant on Xoo. The activities of enzymes related to respiration and the energy metabolism of Xoo were significantly inhibited, while the level of intracellular reactive oxygen species was greatly increased. Scanning electron microscopy observations showed folds on the surface of Xoo. A significant increase in cell membrane permeability and outer membrane permeability and a decrease in cell membrane fluidity resulted in the extravasation of intracellular substances and cell death. The results of this study highlight the role of B. laterosporus SN19-1 against the pathogen of BLB and help elucidate the underlying molecular mechanisms.

Dissipation rates and residue levels of diflubenzuron and difenoconazole on peaches and dietary risk assessment.

The dissipation kinetics, residue levels, and potential risks of diflubenzuron and difenoconazole on peaches were investigated under open field conditions. Two years of field trials were carried out in Shanghai, China, and the half-lives of diflubenzuron and difenoconazole on peaches ranged from 4.4 to 25d. Their terminal residue concentrations on peaches were 0.022-5.7 mg/kg after three of the tested sampling intervals. Based on the maximum residue levels (MRLs) of difenoconazole on peaches, a preharvest interval (PHI) of 14 d was proposed. A PHI of 10 d was proposed for diflubenzuron after a dietary safety assessment. During the safety assessment, the hazard quotient (HQ) and risk quotient (RQ) on peaches were determined. The results showed that the HQs (3.6-8.3%) and RQs(51-55%) of diflubenzuron were acceptable, proving that diflubenzuron poses no potential health risks. For difenoconazole, the HQs (0.027-0.071%) were satisfactory, but the RQs (115-116%) exceeded 100%, which indicated potential risk.

An open tubular capillary electrochromatography column with porous inner surface for protein separation.

An open tubular capillary electrochromatography (OTCEC) column using sole porogen to form porous inner surface has been developed. The porous layer was coated on the capillary inner wall by in situ polymerization in the presence of porogen. The results show that the columns using 1-propanol as sole porogen are appropriate for protein separation. It has higher separation efficiency than the column with the usual coporogen due to much more micropores and mesopores on the porous surface and a higher specific surface area. In addition, the sensitivity of the prepared OTCEC column was improved greatly compared with the dynamically coated capillary with polyvinylpyrrolidone.

Simultaneous Detection of Multiple Plant Growth Regulator Residues in Cabbage and Grape Using an Optimal QuEChERS Sample Preparation and UHPLC-MS/MS Method.

BACKGROUND: At present, plant growth regulators (PGRs) are widely used in agricultural and forestry production. PGRs, like traditional pesticides, have certain toxicities. Naively excessively applying them will cause the acute and chronic poisoning of humans and animals and potentially harm human health. OBJECTIVE: In order to assess, prevent, and control the residues of PGRs in fruits and vegetables, a set of quick, easy, cheap, effective, rugged, and safe (QuEChERS) analytical methods that simultaneously detect multiple PGR residues are urgently needed for quality and safety inspection of agricultural product. METHODS: In this study, grapes (representative of fruits) and cabbages (representative of vegetables) were used as the detected objects. The 30 commercial product residues of PGRs were detected in both with an ultra-high performance liquid chromatography (UHPLC)-tandem mass spectrometry (MS/MS) method, based on optimized chromatographic, MS, and preparation conditions (extraction solvent and cleanup conditions). Grape and cabbage samples were extracted with acetonitrile containing 5% (v/v) acetic acid, dehydrated using a salt package, purified using the QuEChERS method, ionized using electrospray ionization under positive and negative ion switching mode, detected using multi-reaction monitoring, and quantification using an external standard method of matrix matching standard curve. RESULTS: Methanol was selected as the strong elution phase. A methanol-0.1% formic acid-5 mmol/L ammonium acetate solution was selected as the best mobile phase. The optimal extraction solvent was acetonitrile containing 5% acetic acid. Primary secondary amine cleanup could met the determination requirements of PGR residues. The developed method for determination of 30 commercial products of PGR, such as betaine, showed excellent linearity in 1-500, 10-1000, ∼500, ∼2000, and 100-10 000 µg/kg (R ≥ 0.98). At the 0.001 (0.01), 0.05, 0.20, and 1.00 mg/kg additive concentrations, the average addition standard recovery of 30 commercial products of PGR were 61-132% with the relative standard deviations of 1-14% and the LOQs were confirmed to be 1.0-100 µg/kg through the actual addition values of samples. CONCLUSION: The set of optimized QuEChERS UHPLC-MS/MS methods simultaneously detect residues of PGRs in fruits and vegetables with one-time sample preparation for high-throughput, rapid quantitative screening, and confirmation. The methods cover a wide range of PGRs with simple and convenient preparation and small amounts of solvent, and can provide technical support for the supervision of PGR residues in fruits and vegetables. HIGHLIGHTS: The optimizations of extraction solvent screening, different ratios of various purification packages in the QuEChERS method, and UPLC-MS conditions were conducted and the precision, sensitivity, and recovery rates of the methods were investigated in order to establish a QuEChERS UPLC-MS/MS method for simultaneously detecting 30 kinds of PGR residues in fruits and vegetables. The methods allow high-throughput determination of multiple PGR residues in fruits and vegetables and can also provide technical references for related compound residue detection of other matrixes.

Benzodithiophene-Dithienylbenzothiadiazole Copolymers for Efficient Polymer Solar Cells: Side-Chain Effect on Photovoltaic Performance.

A new series of low band gap D-A alternating polymers based on 4,5-bis((2-ethylhexyl)oxy)benzo[2,1- b:3,4- b']dithiophene (BDT) and 5-fluoro-4,7-bis(4-alkylthien-2-yl)benzo[ c][1,2,5]thiadiazole bearing different size of lateral alkyl substituents, namely, PfBB- n, n = 8, 10, 12, 14, and 16, was designed and synthesized for high-performance bulk heterojunction (BHJ) polymer solar cells (PSCs). PfBB- n-bearing linear alkyl side chains exhibited strong and controllable aggregation in both solution and solid states, which gives rise to a significant bathochromic shift of the absorption cut-off down to ∼780 nm in thin film. In addition, the strong and wide absorption (350-800 nm) of PfBB- n polymers can compensate for the relatively weak absorption of PC71BM, particularly in the 300-400 range nm to enhance light harvesting of such an active blend. BHJ solar cells based on PfBB- n:PC71BM blends as an active layer showed power conversion efficiency (PCE) in the range 7.8-9.7%. Because of the strong stacking interchain interactions, PfBB-12-based PSC exhibited aggregation-induced spectral broadening, superior structural order, higher exciton dissociation, higher and more balanced charge carrier mobilities, as well as reduced recombination losses. As a result, PfBB-12-based device afforded the best PCE of 9.7%, with the highest short-circuit current density ( Jsc) of 16.6 mA cm-2 and open-circuit voltage ( Voc) of 0.92 V among devices fabricated. These results demonstrate that the alkyl side chain of the polymer significantly affects the absorption, morphology, and electronic properties of the active blend of PfBB- n/PC71BM, which would provide an alternative useful tool to fine-tune the device performance. Our results also highlight that the electron-rich benzo[2,1- b:3,4- b']dithiophene building block, BDT, is highly useful for the construction of low band gap D-A polymer for highly efficient PSCs.

[Separation performance of vancomycin-bonded stationary phase].

Vancomycin is one of the macrocyclic antibiotics with complex molecular structure. Based on the various functional groups of vancomycin, a vancomycin-bonded stationary phase using glutaraldehyde as the spacer was prepared. Its chromatographic properties in reversed-phase, ion exchange and hydrophilic phase modes were investigated separately. The prepared stationary phase showed the typical characteristic of the reversed-phase stationary, when the organic solvent content was low in the mobile phase. On the contrary, its chromatographic characteristic transformed into hydrophilic phase mode with the organic solvent content increased in the mobile phase. Owing to the amino groups of vancomycin, ion exchange mode can also be applied to the separation method development. The vancomycin-bonded stationary phase was applied to the separation of eight achiral drugs and stevioside in reversed-phase, ion exchange and hydrophilic phase modes. The separations were achieved in three different kinds of separation modes by using appropriate chromatographic conditions. The results provide guidance for the design of new types of stationary phase, and method development of chromatographic stationary phases modified by special compounds with complex construction in corresponding separation modes.