Electrochemiluminescent properties of carbon nitride nanoflowers and their application to the detection of melatonin in foods.

Carbon nitride nanoflower materials (CNNFs) modified electrodes were prepared and used as electrochemiluminescence (ECL) sensors for the sensitive detection of melatonin (MT) in food. The luminescence intensity of CNNFs is increased by 4.6 times compared with bulk g-C3N4. In addition, the effect of dissolved oxygen on the material was eliminated, and the stability of ECL intensity of CNNFs was improved. Under the optimal experimental conditions, there is a good linear relationship between the ECL intensity ratio and logCMT in a concentration range of 2.0 × 10-11-1.0 × 10-6 mol/L, and the detection limit is 6.2 × 10-13 mol/L. This experiment has been successfully used for the detection of MT in rice, black rice, oats, apples, bananas, grapes, carrots, tomatoes, cucumbers, bread, and beers. The results are consistent with those obtained by high-performance liquid chromatography (HPLC). Therefore, this sensor is a sensitive and effective method for detecting MT content in food.

Inverted loading strategy regulates the Mn-OV-Ce sites for efficient fenton-like catalysis.

Regulating interfacial active sites to improve peroxymonosulfate (PMS) activation efficiency is a hot topic in the heterogeneous catalysis field. In this study, we develop an inverted loading strategy to engineer asymmetric Mn-OV-Ce sites for PMS activation. Mn3O4@CeO2 prepared by loading CeO2 nanoparticles onto Mn3O4 nanorods exhibits the highest catalytic activity and stability, which is due to the formation of more oxygen vacancies (OV) at the Mn-OV-Ce sites, and the surface CeO2 layer effectively inhibits corrosion by preventing the loss of manganese ion active species into the solution. In situ characterizations and density functional theory (DFT) studies have revealed effective bimetallic redox cycles at asymmetric Mn-OV-Ce active sites, which promote surface charge transfer, enhance the adsorption reaction activity of active species toward pollutants, and favor PMS activation to generate (•OH, SO4•-, O2•- and 1O2) active species. This study provides a brand-new perspective for engineering the interfacial behavior of PMS activation.

Spatial confinement of styryl pyridine salt derivative in MCM-22 molecular sieve network for boosted fluorescence emission and stable ratiometric sensing of bacillus anthracis biomarkers.

In this work, a stable ratiometric nanofluorescent probe for the detection of 2,6-dipicolinic acid (DPA), a Bacillus anthracis biomarker, was developed based on confinement-induced emission enhancement of cationic styrylpyridine salt derivative L in MCM-22 molecular sieve pores. The cationic L and the lanthanide Tb3+ were loaded into the pores of the molecular sieve by electrostatic interaction with the negatively charged AlO4 tetrahedron unit, and L exhibited enhanced red fluorescence emission as a stable fluorescence reference mark in the nanoprobe platform due to the restricted molecular torsion of L in the pores of MCM-22. At the same time, the characteristic green fluorescence emission of Tb3+ can be excited by energy transfer due to the "antenna effect" of DPA. The prepared Tb-L@MCM-22 nanoprobe showed specific selectivity and stable fluorescence ratiometric detection of DPA in tap water, lake water, bovine serum and actual bacterial spores. Benefiting from the confinement-induced fluorescence enhancement effect of L in the MCM-22 molecular sieve pores, the obtained Tb-L@MCM-22 can provide a stable reference signal for the fluorescence ratiometric detection of DPA with a limit of detection (LOD) of 78.6 nM and 1.310 × 104 spores per mL. More importantly, combining of the Tb-L@MCM-22 based DPA detection test strips with a smartphone app demonstrated a stable, convenient and rapid method for detecting of anthrax biomarkers.

Two novel phosphorus/potassium-degradation bacteria: Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 and their application in two-stage composting of corncob residue.

For effective utilization of corncob residue to realize green circular production, using composting to obtain a high-quality and low-cost biomass fertilizer has become a very important transformation avenue. In this paper, two novel phosphorus/potassium-degradation bacterial strains were isolated from tobacco straw and identified as Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 (abbreviated as SD-1/SD-3). These identified two novel bacteria SD-1/SD-3 show that the soluble phosphorus content of SD-1/SD-3 reached 360.89 mg L-1/403.56 mg L-1 in the shake flask test, and the mass concentration of soluble potassium is 136.56 mg L-1/139.89 mg L-1. In addition, the Laccase (Lac), Lignin peroxidase (LiP), and Manganese peroxidase (MnP) activities of SD-1 and SD-3 are 54.45 U L-1/394.84 U L-1/222.79 U L-1 and 46.27 U L-1/395.26 U L-1/203.98 U L-1 respectively, with the carboxy-methyl cellulase (CMCase) of 72.07 U mL-1 and 52.69 U mL-1. Meanwhile, the effects of three different combinations of cultures, i.e., no inoculation (K1), inoculation of SD-1/SD-3 on day 21 (K2) and on day 0 (G) are investigated to understand the influence on the degradation degree of corncob residue compost. The results of K2 compost treatment showed that the effective P/K content increased nearly 3.1/2.4 times, the degradation of cellulose/lignin was 49.1/68.0%, and the germination rate was 110.23%, which were higher than other experiment groups K1/G. In conclusion, knowledge of this paper will be very useful for the industrial sector for the treatment of complex corncob residue.

Ion exchange fabrication of lanthanide functionalized layered double hydroxides microcapsules for rapid and visual detection of anthrax biomarker.

Lanthanide ion probes have recently been considered as promising sensing materials due to their high sensitivity and good optical properties. Herein, the 3D hierarchical lanthanide functionalized layered double hydroxides microcapsules were synthesized via a facile ion exchange strategy and further developed as novel fluorescent probes for detecting trace amounts of the anthrax biomarker dipicolinicacid (DPA). Benefiting from the 3D porous superstructure and abundant unsaturated coordination sites of lanthanide ion, the ternary Ni-Fe-Ln-LDHs (Ln = Tb/Eu) not only possess a large reactive contact area to improve the sensitivity of DPA detection, but also demonstrate very fast reaction rate. The design of inexpensive fluorescent test strips can perform the on-site and real-time detection via a smartphone with a color recognition application. More prominently, the sensitivity of the system was evaluated by actual spore samples with the detection limit as low as 3.54 × 104 spores/mL. The 3D lanthanide functionalized LDHs nanoprobe constructed by ion exchange exhibits a new vision for the development of a sensing platform in other research areas.

Iodine(III) promotes cross-dehydrogenative coupling of N-hydroxyphthalimide and unactivated C(sp3)-H bonds.

Cross-dehydrogenative coupling reactions provide a method to construct new chemical bonds by direct C-H activation without any pre-functionalization. Compared to functionalization of a C-H bond α- to ether oxygen, α- to carbonyl, or at a benzylic position, functionalization of unactivated hydrocarbons is difficult and often requires high temperatures, a transition-metal catalyst, or a superstoichiometric quantity of volatile, toxic, and explosive tert-butylhydroperoxide. Here, a cross-dehydrogenative C-O coupling reaction of N-hydroxyphthalimide with unactivated alkanes, nitriles, ethers, and thioethers has been realized by using iodobenzene diacetate as the radical initiator. The current protocol enables efficient functionalization of unactivated hydrocarbons and nitriles through inert C(sp3)-H bond activation under mild reaction conditions. O-substituted NHPI derivatives are generated in good yields under metal-free conditions.

Ethanol and KOH co-pretreatment towards ultra-high specific surface area carbons for high-rate and high-energy supercapacitors.

A new avenue for fabricating ultra-high specific surface area (SSA) carbons with hierarchical porous and excellent energy storage ability is achieved from the biomass-waste of pitaya peel with the pre-treating process by ethanol and KOH to optimize the microstructure and porosity, displaying excellent supercapacitance in different electrolytes.

Electrosynthesis of 2-(1,3,4-Oxadiazol-2-yl)aniline Derivatives with Isatins as Amino-Attached C1 Sources.

An intramolecular decarboxylative coupling reaction for the construction of 2-(1,3,4-oxadiazol-2-yl)aniline derivatives was developed from readily available isatins and hydrazides by virtue of electrochemistry. In this reaction, isatins were employed as amino-attached C1 sources, providing a variety of 2-(1,3,4-oxadiazol-2-yl)aniline derivatives with moderate to good yields.

A novel lignin degradation bacteria-Bacillus amyloliquefaciens SL-7 used to degrade straw lignin efficiently.

Using tobacco straw (Ts) and lignin as the sole carbon source, a strain was isolated from Ts and identified as Bacillus amyloliquefaciens SL-7 by 16S rDNA gene-sequencing technology.7-day incubation of Bacillus amyloliquefaciens SL-7 can reduce the chemical oxygen demand (COD) by 69.35% in lignin mineral salt medium. The activity of Manganese peroxidase (MnP) reached maximum level 258.57 U L-1, and Lignin peroxidase (Lip) was 422.68 U L-1 at 4th day. The highest Laccase (Lac) activity (55.95 U L-1) was observed at 3th day. After straw-liquid fermentation degradation of 15 days, the bacterial could degrade 28.55% lignin of the straw which was close to that of fungi. Compared with the control group and effective microorganisms (EM) group, the lignin degradation rate in Bacillus amyloliquefaciens SL-7 group increased by 22.26% and 11.70% at 41-day compost fermentation of tobacco straw. These show the strain has strong lignin degradation performance.

Design, synthesis and anticancer activity of naphthoquinone derivatives.

Basis on molecular docking and pharmacophore analysis of naphthoquinone moiety, a total of 23 compounds were designed and synthesised. With the help of reverse targets searching, anti-cancer activity was preliminarily evaluated, most of them are effective against some tumour cells, especially compound 12: 1-(5,8-dihydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-4-methylpent-3-en-1-yl-4-oxo-4-((4-phenoxyphenyl)amino) butanoate whose IC50 against SGC-7901 was 4.1 ± 2.6 µM. Meanwhile the anticancer mechanism of compound 12 had been investigated by AnnexinV/PI staining, immunofluorescence, Western blot assay and molecular docking. The results indicated that this compound might induce cell apoptosis and cell autophagy through regulating the PI3K signal pathway.

Synthesis of carbon-dots@SiO2@TiO2 nanoplatform for photothermal imaging induced multimodal synergistic antitumor.

For facilitating theranostic nanoplatform with multimodal therapeutic ability, we develop the core-shell structured CDs@SiO2@TiO2 nanoplatforms (CST NPs). The designed CST NPs possess excellent photothermal effect and fluorescence resonance energy transfer (FRET) induced photodynamic property, which could achieve synergistic photothermal and photodynamic therapy. Meanwhile, the photothermal ability of CST NPs acts as a key role in the application of real-time photothermal imaging, benefitting for the diagnosis of tumor accurately. Moreover, the obtained CST NPs also exhibit outstanding sonodynamic effect with huge potential for sonodynamic therapy. Under the 650 nm laser irradiation, the synthesized CST NPs not only inhibit the growth of cancer cells in vitro, but also display precise photothermal imaging and photo-induced ablation to tumor in vivo. As a result, the prepared CST NPs may potentially serve as multifunctional nanoplatform for theranostic antitumor and pave the avenue for clinic cancer therapy.

Binding Characteristics and Superimposed Antioxidant Properties of Caffeine Combined with Superoxide Dismutase.

The binding characteristics and superimposed antioxidant properties of caffeine combined with copper/zinc superoxide dismutase (SOD) were studied. The superimposed antioxidant activity of caffeine with SOD was investigated by detecting the concentration of malondialdehyde (MDA) present in cells, which was induced by hyperthermia and heavy metal exposure. The interactions between the SOD enzyme and caffeine were researched by ultraviolet spectrum, fluorescence spectrum, and molecular computation. The relative amounts of MDA contents of caffeine (0.1 mmol/L), SOD (0.1 mg/L), and caffeine (0.1 mmol/L) and SOD (0.1 mg/L) to water in cells were 0.70, 0.72, and 0.54, respectively, indicating that the antioxidant properties of caffeine combined with SOD may be superimposed. The fluorescence spectroscopy and molecular computation results show that the mixture of caffeine and SOD can result in the formation of a 1:1 complex through hydrogen bond and van der Waals forces spontaneously. The binding constant (K a) of caffeine with SOD at five different temperatures are 4.41 × 104, 3.30 × 104, 2.29 × 104, 1.71 × 104, and 1.17 × 104 L/mol. The changes of Gibbs-free energy (ΔG) are -26.50, -26.21, -25.71, -25.12, and -24.29 KJ/mol and the ΔG of molecular docking calculation is -26.95 KJ/mol. The experimental results are in accordance with the results of theoretical calculations. The combination of caffeine with SOD can change the conformation and microenvironment of SOD but does not change the activity of SOD. In addition, the combination can superimpose the antioxidant activity of caffeine and SOD.

Study on the interaction and antioxidant activity of theophylline and theobromine with SOD by spectra and calculation.

Theophylline (TP) and theobromine (TB) are the methyl derivatives of xanthine. The antioxidation of TP and TB as well as the effect of the antioxidation and activity of copper­zinc superoxide dismutase (SOD) with TP and TB were investigated. The contents of MDA in cells showed that both TP (14.49 µmol/g) and TB (14.25 µmol/g) are active in oxidation resistance and closed to the antioxidant effect of SOD (13.77 µmol/g). With the formation of TP-SOD and TB-SOD, the antioxidant ability can be superimposed. The interactions between TP/TB and SOD were studied by ultraviolet spectrum, fluorescence spectrum and molecular docking. The results showed that the complex of TP/TB and SOD with 1:1 component was stabilized by hydrogen bonding and van der Waals forces. The analysis also indicated that the microenvironment and structure of SOD were changed. All of the results indicate that the complex formation of TP-SOD and TB-SOD can maintain their respective antioxidant effects without changes in the activity of SOD.

Facile synthesis of novel carbon-dots/hemin nanoplatforms for synergistic photo-thermal and photo-dynamic therapies.

Due to the traditional therapies of cancer inducing huge pains to patients, the non-invasive photo-guided therapies are attracting massive attentions of researchers. Herein, the intelligent-designed carbon-dots/hemin nanoplatforms (HCDs NPs) were developed, owning high-authority photo-therapy for cancer. The fluorescence resonance energy transfer (FRET) effect enhanced the photo-thermal ability of HCDs NPs, endowing the synthesized nanoplatforms with photo-dynamic property simultaneously. Therefore, the obtained HCDs NPs could achieve synergetic photo-thermal and photo-dynamic therapies for cancer. Basing on the experimental results, the prepared HCDs NPs could induce the temperature enhancement high to ca 26 °C under laser irradiation, also with the outstanding photo-dynamic efficacy. More than 90% of cancer cells die after 10 min laser treatment. Thus, the dual-modal photo-therapeutic HCDs NPs are promising and excellent nanomaterials for potential application in synergistic cancer therapy.

A highly selective colorimetric and fluorescent chemosensor for Al(III) based-on simple naphthol in aqueous solution.

A colorimetric and fluorescent chemosensor (L) for Al(III) was synthesized and fully characterized. L could be both used as a colorimetric and fluorescent chemosensor for the detection of Al(3+) ions with low detection limit (8.87×10(-7) M) in CH3CN-H2O (1:1, v/v) solution. The binding ratio of L-Al(3+) was determined from the Job plot (absorption and fluorescence spectra) and MALDI-TOF MS data to be 1:1. The binding constant (Ka) of Al(3+) binding to L was calculated to be 4.8×10(5) M(-1) from a Benesi-Hildebrand plot. Moreover, the binding site of L with Al(3+) was determined by (1)H NMR titration experiment.

Characterization of the interaction between superoxide dismutase and 2-oxoisovalerate dehydrogenase.

Thermophiles are attractive microorganisms to study the adaptation of life in high temperature environment. It is revealed that superoxide dismutase (SOD) is essential for thermoadaptation of thermophiles. However, the SOD-mediated pathway of thermoadaptation remains unclear. To address this issue, the proteins interacted with SOD were characterized in Thermus thermophilus in this study. Based on co-immunoprecipitation and Western blot analyses, the results showed that 2-oxoisovalerate dehydrogenase α subunit was bound to SOD. The isothermal titration calorimetry analysis showed the existence of the interaction between SOD and 2-oxoisovalerate dehydrogenase α subunit. The bacterial two-hybrid data indicated that SOD was directly interacted with 2-oxoisovalerate dehydrogenase α subunit. Gene site-directed mutagenesis analysis revealed that the intracellular interaction between SOD and 2-oxoisovalerate dehydrogenase α subunit was dependent on their whole molecules. Therefore our study presented a novel aspect of SOD in the thermoadaptation of thermophiles by interaction with dehydrogenase, a key enzyme of tricarboxylic acid cycle.

Solvent-dependent "turn-on" fluorescence chemosensor for Mg(2+) based on combination of C=N isomerization and inhibition of ESIPT mechanisms.

A fluorescent chemosensor (L) for Mg(2+) has been synthesized and characterized, which exhibits turn-on fluorescence response for Mg(2+) only in alcohol solvent (methanol or ethanol) with high sensitivity and selectivity. But in both nonpolar and polar solvents (cyclohexane, DCM, DMSO or MeCN), L showed negligible fluorescent response for Mg(2+). In order to discover the unique phenomenon, optical measurements, liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) and a high performance liquid chromatography with a fluorescence detector (HPLC-FLD) of L and L with Mg(2+) ions in solvents were studied. In alcohol solvent, [L+alcohol molecule] was formed and the mechanism aspect of L concerning the remarkable fluorescence response for Mg(2+) has been discussed.

Determination of nitrofuran metabolites in shrimp by high performance liquid chromatography with fluorescence detection and liquid chromatography-tandem mass spectrometry using a new derivatization reagent.

A high performance liquid chromatography with fluorescence detection (HPLC-FLD) method for the simultaneous determination of total nitrofuran metabolite residues (furazolidone, furaltadone, nitrofurantoin, and nitrofurazone) in shrimp was developed. The method involves the acid hydrolysis of protein-bound metabolites, followed by the derivatization of the freed metabolites with the new fluorescent derivatization reagent 2-hydroxy-1-naphthaldehyde (HN) and subsequent liquid-liquid extraction (LLE). Separation is achieved on a YMC-Pack Polymer C18 column under alkaline conditions, and the high fluorescence intensity of the derivatives at an emission wavelength Em=463nm (Ex=395nm) enables, for the first time, their simultaneous determination in shrimp at concentrations as low as 1µg/kg by HPLC-FLD. The method was validated using blank shrimp fortified with all four metabolites at 0.5, 1.0 and 2.0µg/kg. Recoveries were >87% with relative standard deviations of <8.1% for all four metabolites. Furthermore, the results obtained by HPLC-FLD were in very good agreement with those obtained by LC-MS/MS analysis.

High-performance liquid chromatography with fluorescence detection for the determination of nitrofuran metabolites in pork muscle.

A simple and sensitive HPLC method with fluorescence detection (HPLC-FLD) is reported for the simultaneous determination of metabolites of four nitrofuran drugs (furazolidone, furaltadone, nitrofurantoin and nitrofurazone) in pork muscle. The method involves acid hydrolysis of the protein-bound drug metabolites and the conjugation of the released side-chains with a novel fluorescence agent 2-hydroxy-1-naphthaldehyde. After liquid-liquid extraction and effective separation of the derivatives on a YMC-Pack Polymer C18 column at 40°C under alkaline conditions, the high fluorescence intensity of these derivatives at emission wavelength λem = 463 nm enables their simultaneous determination in pork muscle at concentrations as low as 1 µg kg⁻¹. The method was validated using blank pork muscle fortified with all four metabolites at 0.5, 1.0 and 2.0 µg kg⁻¹. Recoveries were > 92.3% with RSDs < 8.5% for all four metabolites. The results obtained with HPLC-FLD and LC-MS/MS methods showed very good agreement for pork muscle samples.

The binding characteristics of isoniazid with copper-zinc superoxide dismutase and its effect on enzymatic activity.

BACKGROUND: Isoniazid (INH) is front-line anti-tuberculosis (TB) drugs, which are usually prescribed to TB patients for a total period of 6 months. Antituberculosis drug-induced hepatotoxicity (ATDH) is a serious adverse reaction of TB treatment. It is reported that INH-induced hepatotoxicity is associated with oxidative stress. Superoxide dismutase (SOD, EC 1.15.1.1) is the key enzyme for the protection of oxidative stress, which catalyzes the removal of superoxide radical anion, thereby raising the need to better understand the interaction between INH and SOD. RESULTS: The experimental results showed that the fluorescence intensity of Cu/Zn-SOD regularly decreased owing to form a 1:1 INH-SOD complex. According to the corresponding association constants (K SV) between INH and SOD obtained from Stern-Volmer plot, it is shown that values of K A are 1.01 × 10(4), 5.31 × 10(3), 3.33 × 10(3), 2.20 × 10(3) L · mol(-1) at four different temperatures, respectively. The binding constants, binding sites and the corresponding thermodynamic parameters ((Δ) H, (Δ) G and (Δ) S) were calculated. A value of 3.93 nm for the average distance between INH and chromophore of Cu/Zn-SOD was derived from Förster theory of non-radiation energy transfer. The conformational investigation showed that the presence of INH resulted in the microenvironment and conformational changes of Cu/Zn-SOD. In addition, Effects of INH on superoxide dismutase activity was examined. CONCLUSIONS: The results show that the hydrogen bonding and van der Waals forces play major roles in stabilizing the 1:1 INH-SOD complex. After addition of INH during the range of the experiment, the conformation and microenvironment of Cu/Zn-SOD are changed, but the activity of Cu/Zn-SOD is not changed.