Simultaneous detection of TNOS and P35S in transgenic soybean based on magnetic bicolor fluorescent probes.

A magnetic-separation-dual-targets fluorescent biosensor was fabricated to detect terminator nopaline synthase (TNOS) and promoter of cauliflower mosaic virus 35s (P35S) in transgenic soybean based on incorporation of bicolor CdTe quantum dots carried by silica nanospheres. In this protocol, the fixed probes for TNOS or P35S were magnetized firstly with Fe3O4@Au magnetic nanosphere by Au-S covalent bonding to achieve magnetized probes. Meanwhile, the capture probes for TNOS or P35S were functionalized with green or red fluorescent microspheres respectively to obtain fluorescently-labeled probes, which could emit relative strong green or red fluorescent signal. Two terminals of TNOS or P35S were recognized by magnetized probes and fluorescently-labeled probes respectively to form the sandwiched structures in the process of biosensor development subsequently, and it was separated by a magnet instantly. The fluorescence intensities of remnant supernatant were measured and analyzed accordingly to achieve simultaneous detection of TNOS and P35S. This biosensor exhibited a good dynamic range, low limit of detection and excellent selectivity in detecting transgenic soybean.

Aptamer-functionalized chitosan magnetic nanoparticles as a novel adsorbent for selective extraction of ochratoxin A.

The preparation and application of aptamer-functionalized chitosan magnetic nanoparticles (Fe3O4@CTS@Apt nanoparticles) for selective extraction and determination ochratoxin A (OTA) were described in this study. Magnetic nanoparticle was synthesized by the coprecipitation method followed by coating with chitosan to improve its stability and biocompatibility. Further characterization was performed by scan electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and magnetic property measurement, and the results clearly indicated that the obtained magnetic chitosan nanoparticle was composed of magnetic core and chitosan coating layer. Aptamers specific to OTA were coupled onto the magnetic chitosan nanoparticles, and an extraction procedure was developed by optimization. When challenged with food samples fortified with OTA at 5 and 10 µg/kg, recoveries ranging from 91.3% to 99.1% with relative standard deviation (RSD) ≤ 4.2% were achieved by aptamer-functionalized magnetic extraction, which is very close to the results obtained by immunoaffinity chromatography extraction, indicating that this magnetic adsorbent could be hopefully used to achieve a fast and efficient extraction and detection of OTA in food samples.

Chitosan microparticle-based immunoaffinity chromatography supports prepared by membrane emulsification technique: Characterization and application.

In this study, chitosan microparticles intended to be used as matrix support for immunoaffinity chromatography were prepared by membrane emulsification technique. Regular spherical chitosan microparticles were obtained with an average diameter of 62.9µm and a size distribution index of 1.9 and showed stable under wide pH range (4.0 to 10.0) and various chemical conditions. Size distribution and chemical stability of the prepared chitosan microparticles were relatively close to those of Sepharose 4B. Polyclonal antibody against zearalenone (ZEN) as a model ligand was coupled onto chitosan microparticles or Sepharose 4B to obtain immunoaffinity columns. Further characterization indicated that chitosan microparticle-based column exhibited a maximum binding capacity of 6.1µg/mL gel, higher than that (3.1µg/mL gel) of Sepharose 4B-based column, and a column-to-column variation of 6.0%, slightly lower than that (8.6%) of Sepharose 4B-based column. When challenged with cornmeal samples fortified with ZEN at 50 and 100ng/g, satisfied recoveries of 92.1-100.2% with relative standard deviation (RSD)≤7.6% and 88.3-107.3% with RSD≤7.6% were both yielded by chitosan microparticle- and Sepharose 4B-based column, respectively, indicating that the obtained chitosan microparticles could be hopefully used as matrix support for immunoaffinity chromatography with reproducible extraction behavior and high extraction efficiency.

Feasibility study on direct fermentation of soybean meal by Bacillus stearothermophilus under non-sterile conditions.

BACKGROUND: To evaluate the feasibility of high-temperature solid-state fermentation (SSF) using soybean meal (SBM) during the non-sterile process, Bacillus stearothermophilus was employed to assess the nutritional quality and bioactivity of SBM after fermentation. RESULTS: The fermented SBM (FSBM) without autoclaving showed significant improvements in nutritional quality and bioactivity. The contents of peptides and crude and soluble proteins increased by 131.21%, 5.3% and 15.52%, respectively. Meanwhile, DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging ability, reducing ability and hydroxyl free radical-scavenging activity rose by 57.07%, 238.92% and 368.26%, respectively. The inhibitory activity of angiotensin I-converting enzyme increased from 1.43 ± 0.83% to 26.89 ± 1.03%, while the trypsin inhibitor activity decreased by 74.05%. The contents of neutral and alkaline proteases and the growth of microorganisms in FSBM without autoclaving were higher and better than in steam-treated FSBM. After steam treatment, the water-holding capacity of SBM decreased, and a high crosslink density was observed on the surface of SBM particles. CONCLUSIONS: It is feasible to ferment SBM by high-temperature SSF using B. stearothermophilus under non-sterile conditions. Adverse effects of SSF using sterile SBM might be owing to the low water-holding capacity caused by autoclaving. © 2018 Society of Chemical Industry.

Enantioselective addition of selenosulfonates to α,ß-unsaturated ketones.

An organo-catalyzed enantioselective addition of selenosulfonates to α,ß-unsaturated ketones was developed for the first time. With a chiral squaramide as an efficient catalyst, the desired α-selenylated ketones were obtained in a good yields with high enantioselectivity up to 89% ee, and good results could be obtained on a gram scale. The products could also be efficiently transformed into useful building blocks with a propenylic stereocenter; the strategy presented in this study may find further applications in organic synthesis.

Enantioselective Synthesis of anti-syn-Trihalides and anti-syn-anti-Tetrahalides via Asymmetric ß-Elimination.

Structural motifs containing contiguous halide-bearing stereocenters are common in natural products as well as bioactive molecules. A few successful examples have been reported in the area of asymmetric vicinal dihalogenation of alkenes for accessing dihalogenated products; in this report, an alternative generation method of contiguous halide-bearing stereocenters α,ß,γ,δ relative to carbonyl group in excellent enantioselectivity is proposed by utilizing a Song's oligoEG catalyst-catalyzed asymmetric ß-elimination. According to this methodology, a wide range of anti-syn-trihalides and anti-syn-anti-tetrahalides with high levels of enantioselectivity were synthesized. The synthetic utility of the contiguous halide-bearing stereocenters was demonstrated by several transformations. The results of high-resolution mass spectrometry indicated that the favorable interaction between catalyst and one of the enantiomers of racemic contiguously multihalogenated ketone contributed to the original enantioselectivity of dehydrohalogenation. A deuterium kinetic isotope effect experiment revealed that this ß-elimination reaction proceeds by the E2 mechanism. This strategy opens a new pathway for the asymmetric synthesis of contiguous halide-bearing stereocenters of great complexity.

Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes via in Situ Generated Chiral Fluoride-Catalyzed Cascade Sulfa-Michael/Aldol Reaction of 1,4-Dithiane-2,5-diol and α,ß-Unsaturated Ketones.

A chiral fluoride-catalyzed asymmetric cascade sulfa-Michael/aldol condensation reaction of 1,4-dithiane-2,5-diol and a series of α,ß-unsaturated ketones is described to access chiral trisubstituted tetrahydrothiophene derivatives. The target products, including the spiro tetrahydrothiophene derivatives bearing a five-, six-, and seven-membered ring, were highly functionalized and showed high ee value. This established protocol realized a highly enantioselective reaction with a catalytic amount of KF and Song's chiral oligoEG via in situ generated chiral fluoride to construct useful heterocyclic skeletons with great complexity.