Development of a receptor based signal amplified fluorescence polarization assay for multi-detection of 35 sulfonamides in pork.

With the increasing focus on food security, a screening method with high-throughput, ultra-sensitivity, and user-friendly operation is urgently needed for monitoring of sulfonamides residues in animal-derived foods. In this study, the sulfonamides' receptor dihydropteroate synthase of Staphylococcus aureus was subjected to saturate mutation, and a mutant with higher affinities for sulfonamides was obtained. The mutant was then used as recognition material to establish a fluorescence polarization assay for determination of 35 sulfonamides in pork. Due to the use of an enhanced fluorescent tracer containing two fluorophore molecules, the sensitivities for the 35 sulfonamides were improved for 2.8-8.6 folds (LODs 0.03-1.16 ng/mL) in comparison with using conventional fluorescent tracer. The present method outperformed all previous fluorescence polarization (immuno)assays for sulfonamides due to its broader spectrum, higher sensitivity, and shorter assay time. Furthermore, this is the first study reporting an enhanced fluorescence polarization assay for determination of small molecule substance.

Protocol for engineering E. coli Nissle 1917 to diagnose, record, and ameliorate inflammatory bowel disease in mice.

Engineered microorganisms hold potential for disease diagnosis and treatment. Here, we present a protocol to engineer E. coli Nissle 1917 strain (iROBOT) using genome insertion and plasmid construction to diagnose, record, and ameliorate inflammatory bowel disease in mice. We describe steps for constructing and administering iROBOT, diagnosing and recording colitis, preparing samples, and analyzing fluorescence and base editing ratios of iROBOT. We detail a colitis ameliorating assay using the disease activity index, colon length, tissue pathological section, and cytokine analysis. For complete details of the use and execution of this protocol, please refer to Zou et al.1.

Chromium-Catalyzed Defluorinative Reductive Coupling of Aldehydes with gem-Difluoroalkenes.

Herein, a mild and convenient defluorinative reductive cross coupling of gem-difluoroalkenes with aliphatic aldehydes has been developed to afford diverse silyl-protected ß-fluorinated allylic alcohols. The reaction is operationally simple and shows good functional group tolerance with moderate to excellent yields. The utility of this method is demonstrated by converting the products into various bioactive fluorinated compounds, showing its potential applications in drug discovery and biochemistry.

Identification and Characterization of an O-Succinyl-L-Homoserine Sulfhydrylase From Thioalkalivibrio sulfidiphilus.

L-methionine is an important natural amino acid with broad application prospects. A novel gene encoding the enzyme with the ability to catalyze O-succinyl-L-homoserine (OSH) to L-methionine was screened and characterized. The recombinant O-succinyl-L-homoserine sulfhydrylase from Thioalkalivibrio sulfidiphilus (tsOSHS) exhibited maximum activity at 35°C and pH 6.5. OSHS displayed an excellent thermostability with a half-life of 21.72 h at 30°C. Furthermore, the activity of OSHS increased 115% after Fe2+ added. L-methionine was obtained with a total yield reaching 42.63 g/L under the concentration of O-succinyl-L-homoserine 400 mM (87.6 g/L). These results indicated that OSHS is a potential candidate for applying in the large-scale bioproduction of L-methionine.

Key role of exopolysaccharide on di-butyl phthalate adsorbing by Lactobacillus plantarum CGMCC18980.

Plasticizers belong to hormone-like substances existing widely in the environment. According to the Environmental Protection Agency of China, they are considered to be the fourth class of toxic chemicals due to their harmful effects on normal endocrine system in human bodies. In the recent published work of our lab, Lactobacillus plantarum CGMCC18980 (strain P1) could reduce the toxicity of di-butyl phthalate (DBP) in rats effectively. The purpose of this study is to further explore the adsorption mechanism of di-butyl phthalate to L. plantarum CGMCC18980, based on optimizing the adsorption conditions. As a consequence, the adsorption effect of L. plantarum CGMCC18980 attributed to relationships between exopolysaccharide, membrane protein, and the cell wall. Experimental results demonstrated that exopolysaccharide and the cell wall were devoted to DBP binding. An obvious adsorption layer was observed outside of L. plantarum CGMCC18980 through scanning electron microscope (SEM) and transmission electron microscope (TEM). The Fourier transform infrared spectroscopy (FTIR) results showed that the functional groups involved in adsorption were mainly C=O, C-N, and C-O, which related to lipids and polysaccharides. Zeta potential analysis indicated that DBP adsorption had no significant relationship with surface charge. These results revealed that exopolysaccharide may be the key factor of strain CGMCC18980 in DBP adsorption. KEY POINTS: • Lactobacillus plantarum CGMCC18980 has the ability to adsorb di-butyl phthalate, reaching to 58.63%. • Exopolysaccharide is considered to play a key role in adsorption process. • Membrane protein, cell wall, and surface charge do not contribute to adsorption.

New strategy for designing promising mid-infrared nonlinear optical materials: narrowing the band gap for large nonlinear optical efficiencies and reducing the thermal effect for a high laser-induced damage threshold.

To circumvent the incompatibility between large nonlinear optical (NLO) efficiencies and high laser-induced damage thresholds (LIDTs) in mid-infrared NLO materials, a new strategy for designing materials with both excellent properties is proposed. This strategy involves narrowing the band gap for large NLO efficiencies and reducing the thermal effect for a high LIDT. To support these proposals, a series of isostructural chalcogenides with various tetrahedral center cations, Na2Ga2MQ6 (M = Ge, Sn; Q = S, Se), were synthesized and studied in detail. Compared with the benchmark AGS, these chalcogenides exhibit significantly narrower band gaps (1.56-1.73 eV, AGS: 2.62 eV) and high NLO efficiencies (1.6-3.9 times that of AGS at 1910 nm), and also outstanding LIDTs of 8.5-13.3 × those of AGS for potential high-power applications, which are contrary to the conventional band gap view but can be attributed to their small thermal expansion anisotropy, surmounting the NLO-LIDT incompatibility. These results shed light on the search for practical IR NLO materials with excellent performance not restricted by NLO-LIDT incompatibility.

Thiophosphates Containing Ag+ and Lone-Pair Cations with Interchiral Double Helix Show Both Ionic Conductivity and Phase Transition.

Quaternary metal thiophosphates containing second-order Jahn-Teller distorted d10 Ag+ and lone-pair cations, Ag3Bi(PS4)2 (1), Ag7Sn(PS4)3 (2), and Ag7Pb(PS4)3 (3), were obtained by solid-state synthesis. The structural frameworks of 2 and 3 feature an infinite 1-D interchiral double helix ∞1(Ag3P2S11), which is rare in inorganic compounds. Compound 3 undergoes a significant first-order structural phase transition from monoclinic to hexagonal at ∼204 °C. This can be ascribed to the significant mismatch in the expansion coefficients between Pb-S (Ag-S) and P-S bonds evaluated by bond valence theory. The three compounds are Ag+ ionic conductors, and Ag+ ion migration pathways are proposed by calculating maps of low bond valence mismatch. Moreover, the optical properties of the three compounds were studied, and electronic structure calculations were performed. The combination of second-order Jahn-Teller distorted d10 cation and lone-pair cation provides a new strategy to explore new metal thiophosphates with interesting structures and promising properties.

Phase Transition and Second Harmonic Generation in Thiophosphates Ag2Cd(P2S6) and AgCd3(PS4)S2 Containing Two Second-Order Jahn-Teller Distorted Cations.

Two new phases in the Ag-Cd-P-S system containing two second-order Jahn-Teller (SOJT) distorted d10 cations (Cd2+ and Ag+), namely, Ag2Cd(P2S6) (1) and AgCd3(PS4)S2 (2), are obtained via medium-temperature solid-state synthesis. Compound 1 exhibits a two-dimensional layered structure and undergoes a first-order structural phase transition at approximately 280 °C. This outcome can be ascribed to the significant mismatch in the expansion coefficients between Cd-S (Ag-S) and P-P (P-S) bonds evaluated through bond valence theory. The three-dimensional non-centrosymmetric (NCS) framework of 2 is constructed by two types of tetrahedral layers consisting of corner-shared CdS4, AgS4, and PS4 tetrahedra. Compound 2 exhibits second harmonic generation (SHG) intensity of 0.45 times that of commercial AgGaS2 (AGS) at a laser irradiation of 1.85 µm and an optical band gap of 2.56 eV, and no intrinsic vibrational absorption of chemical bonds is observed in the range of 2.5-18.2 µm. Both phase transition in 1 and SHG properties in 2 are closely related to the SOJT distorted d10 cations and diverse phosphorus-sulfur polyanions (PaSb)n-, which together can easily result in NCS distorted structures and interesting properties.

Syntheses, Structures, and Nonlinear Optical Properties of Two Sulfides Na2In2MS6 (M = Si, Ge).

The first two new Na-containing sulfides Na2In2MS6 (M = Si (1), Ge (2)) in the Na2Q-B2Q3-CQ2 (B = Ga, In; C = Si, Ge, Sn; Q = S, Se) system were prepared for the first time through conventional high-temperature solid-state reaction. They are isostructural with space group Cc (No. 9) in monoclinic phases and feature three-dimensional frameworks built by the (∞)¹[In2MS6]²â» (M = Si, Ge) chains through corner-sharing InS4 tetrahedra and MS4 (M = Si, Ge) tetrahedra, with Na⁺ cation located in the cavities. They display moderate second harmonic generation (SHG) conversion efficiencies compared with commercial AgGaS2, with phase-matching behavior at 1800 nm and laser-induced damage thresholds 6.9 and 4.0 times higher than that of AgGaS2, respectively. Therefore, the output SHG intensities of 1 and 2 will be ∼4.3 and 4.0 times larger than that of AgGaS2, when the intensity of incident laser increased to close the damage energy of 1 and 2, indicating their potential for high-power nonlinear optical application.

Syntheses, structures, and nonlinear-optical properties of metal sulfides Ba2Ga8MS16 (M = Si, Ge).

Two new metal sulfides, Ba(2)Ga(8)MS(16) (M = Si, Ge), have been synthesized by high-temperature solid-state reactions. They are isostructural and crystallize in the noncentrosymmetric space group P6(3)mc (No. 186) with a = 10.866(5) Å, c = 11.919(8) Å, and z = 2 for Ba(2)Ga(8)SiS(16) (1) and a = 10.886(8) Å, c = 11.915(3) Å, and z = 2 for Ba(2)Ga(8)GeS(16) (2). Their three-dimensional frameworks are constructed by corner-sharing mixed (Ga/M)S(4) (M = Si, Ge) and pure GaS(4) tetrahedra, with Ba(2+) cations filling in the tunnels. Compounds 1 and 2 are transparent over 0.42-20 µm and have wide band gaps of around 3.4 and 3.0 eV, respectively. Polycrystalline 2 displays strong nonlinear second-harmonic-generation (SHG) intensities that are comparable to that of the benchmark AgGaS(2) (AGS) with phase-matching behavior at a laser irradiation of 1950 nm. Of particular interest, compound 2 also possesses a high powder laser-induced damage threshold of ∼22 times that of AGS. The alternate stacking of the mixed (Ga/M)S(4) (M = Si, Ge) tetrahedral layer with the pure GaS(4) tetrahedral layer along the c axis and the alignment of these two types of tetrahedra in the same direction may be responsible for the large SHG signals observed.

New mercury-contained cationic frameworks stabilized by (GaCl4)- unit via weak electrostatic forces in supramolecular compounds (Hg11P4)(GaCl4)4 and (Hg3AsS)(GaCl4).

Two new inorganic supramolecular compounds, (Hg11P4)(GaCl4)4 (1) and (Hg3AsS)(GaCl4) (2), have been prepared by the solid-state reactions. Their structures are characterized by mercury-containing cationic hosts and discrete (GaCl4)(-) guests, which is a derivative of a very strong Lewis acid. The three-dimensional cationic framework of 1, (Hg11P4)(4+), is marvellously extended by Hg2(2+) and Hg3(2+) groups as well as Hg(2+) ions to form two large tunnels with different sizes each embedded with two columns of (GaCl4)(-) anions. Compound 2 features a layered structure with (GaCl4)(-) tetrahedra being intercalated between two-dimensional (Hg3AsS)(+) layers and it is the first mercury pnictidechalcohalide. It is found that the weak electrostatic forces between hosts and guests play a key role in the stabilization of the whole structures of 1 and 2, which is strikingly different from almost all the reported metal pnictidehalide and chalcohalide supramolecular compounds. Optical dielectric constants calculations show that both 1 and 2 possess strong dielectric anisotropy.

Ln3GaS6 (Ln = Dy, Y): new infrared nonlinear optical materials with high laser induced damage thresholds.

Two new ternary rare earth chalcogenides, Dy3GaS6 (1) and Y3GaS6 (2), are reported here. They both crystallize in the orthorhombic space group Cmc21 (no. 36). Both are synthesized in pure phase and show phase-matchable second harmonic generation (SHG) of about 0.2 and 0.5 times, respectively for 1 and 2, as strong as that of KTiOPO4 (KTP) based on the powder SHG measurement at the wavelength of 1910 nm. They possess high powder laser induced damage thresholds (LIDTs), respectively, about 14 and 18 times that of AgGaS2 (AGS) based on the powder LIDT measurements under 1064 nm laser irradiation. They both exhibit wide transparency in the IR region (2.5­25 µm). It is believed that the title compounds are new candidates for nonlinear optical (NLO) materials in the IR region. To gain further insights into the NLO and LIDT properties of 1 and 2, the calculations of second-order NLO susceptibility and lattice energy density (LED) were also performed to explain their SHG efficiencies and high LIDTs.