Copper-catalyzed efficient dithiocyanation of styrenes: Synthesis of dithiocyanates

A novel Cu-catalyzed intermolecular chemoselectivity dithiocyanation of styrenes with ammonium thiocyanate has been developed under mild conditions. This reaction exhibits a wide range of functional-group tolerance in styrenes to afford various dithiocyanates. The reaction mechanism was primarily investigated and a radical process was proposed.     

Ultrasensitive photometric and visual determination of organophosphorus pesticides based on the inhibition of enzyme-triggered formation of core-shell gold-silver nanoparticles

The authors describe a colorimetric assay for the determination of organophosphorous pesticides (OPPs) based on enzyme-triggered deposition of silver nanoparticles on the surface of gold nanoparticles (AuNP). In this method, alkaline phosphatase (ALP) catalyzes the dephosphorylation of the substrate p-aminophenyl phosphate (p-APP) to form p-aminophenol (p-AP) which is capable of reducing Ag(I) ion to Ag metal which is spontaneously deposited on the surface of AuNP to form Au@Ag NPs. As a result, the color of the colloidal solution first changes from red to yellow, and then to gray with further increases in the thickness of the Ag shell. This can be detected visually or by spectrophotometry. OPPs act as inhibitors of ALP so that the dephosphorylation of p-APP is blocked and silver deposition on the AuNP is retarded or completely suppressed. As a result, the color change from red to yellow is less distinct. This finding forms the basis for the determination of OPPs. Under optimum conditions, the absorbance at 370 nm depends linearly on the logarithm of inhibitor concentration over the ranges from 0.05 to 500 μg?L^?1 and from 0.1 to  500 μg?L^?1, with detection limits of 0.025 μg?L^?1 for methamidophos and 0.036 μg?L^?1 for malathion (at an S/N ratio of 3). Both values are much lower than the maximum residue limits specified in the U.S. Department of Agriculture and European Union pesticide regulations. The validation and practicability of this method for the measurement of OPPs was demonstrated by analyzing (spiked) tap water and lake water.

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Graphical abstract The alkaline phosphatase (ALP) activity is inhibited by organophosphorus pesticides (OPPs). As a result, the ALP-trigged formation of core-shell gold-silver nanoparticles depends on the amount of OPPs, which showed different absorbances and colors.

     

Rapid screening,identification, and purification of neuraminidase inhibitors from Lithospermum erythrorhizon Sieb.et Zucc. by ultrafiltration with HPLC–ESI‐TOF‐MS combined with semipreparative HPLC

We put forward an efficient strategy based on bioassay guidance for the rapid screening, identification, and purification of the neuraminidase inhibitors from traditional Chinese medicines, and apply to the discovery of anti‐influenza components from Lithospermiun erythrorhizon Sieb.et Zucc. Ultrafiltration with high‐performance liquid chromatography and electrospray ionization time‐of‐flight mass spectrometry was employed for the rapid screening and preliminarily identification of anti‐influenza components from Zicao. Semipreparative high‐performance liquid chromatography was used for the rapid separation and purification of the target compounds. NMR spectroscopy, mass spectrometry, and UV spectroscopy were used for further structural identification, and the activity of the compounds was verified by in vitro assay. Five compounds were found to have neuraminidase inhibitory activity by this method. Subsequently, the five compounds were separated by semipreparative high‐performance liquid chromatography with the purity over 98% for all of them by high‐performance liquid chromatography test. Combined with the NMR spectroscopy, mass spectrometry, and UV spectroscopy data, they were identified as alkannin, acetylalkannin, isobutyrylalkannin, β,β‐dimethylacryloylalkannin and isovalerylalkannin. The in vitro assay showed that all five compounds had good neuraminidase inhibitory activities. These results suggested that the method is highly efficient, and it can provide platform and methodology supports for the rapid discovery of anti‐influenza active ingredients from complex Chinese herbal medicines.     

Environmentally friendly solid‐phase microextraction coupled with gas chromatography and mass spectrometry for the determination of biogenic amines in fish samples

In this work, a facile and environmentally friendly solid‐phase microextraction assay based on on‐fiber derivatization coupled with gas chromatography and mass spectrometry was developed for determining four nonvolatile index biogenic amines (putrescine, cadaverine, histamine, and tyramine) in fish samples. In the assay, the fiber was firstly dipped into a solution with isobutyl chloroformate as derivatization reagent and isooctane as extraction solvent. Thus, a thin organic liquid membrane coating was developed. Then the modified fiber was immersed into sample solution to extract four important bioamines. Afterwards, the fiber was directly inserted into gas chromatography injection port for thermal desorption. 1,7‐Diaminoheptane was employed as internal standard reagent for quantification of the targets. The limits of detection of the method were 2.98–45.3 μg/kg. The proposed method was successfully applied to the detection of bioamines in several fish samples with recoveries ranging 78.9–110%. The organic reagent used for extraction was as few as microliter that can greatly reduce the harm to manipulator and environment. Moreover, the extraction procedures were very simple without concentration and elution procedures, which can greatly simplify the pretreatment process. The assay can be extended to the in situ screening of other pollutant in food safety by changing the derivatization reagent.     

Metabolomics method based on ultra high performance liquid chromatography with time‐of‐flight mass spectrometry to analyze toxins in fresh and dried toad venom

Drying is a critical step to prolong the storage time in natural medicine processing but it changes the chemical characteristics of the product. In this study, research was performed to characterize the metabolomic changes in toad venom induced by vacuum‐drying at 60°C and air‐drying at room temperature by ultra high performance liquid chromatography coupled with pattern recognition approaches. In total 52 metabolites, down‐regulated or up‐regulated, were identified as potential chemical markers. Compared with fresh toad venom, vacuum‐drying at 60°C succeeded in raising the conjugated‐type bufadienolide content significantly, while the content of free‐type bufadienolides were slightly reduced. On the other hand, toad venom air‐dried at room temperature presented a relatively low amount of bufadienolides compared with fresh venom. For example, the content of several known anti‐tumor components (gamabufotalin, bufotalin, cinobufagin, etc.) were significantly reduced. The 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide bioassay further showed that venom air‐dried at room temperature had weaker anti‐tumor activity on human hepatocellular carcinoma SMMC‐7721 proliferation in vitro than samples vacuum‐dried at 60°C. These results showed that the great metabolomic changes of toad venom occurred during the drying process, suggesting that a proper drying procedure is important for sustaining the chemical quality of natural medicines.     

Fabrication of Thickness‐Controllable Micropatterned Polyelectrolyte‐Film/Nanoparticle Surfaces by Using the Plasma Oxidation Method

We have demonstrated a novel way to form thickness‐controllable polyelectrolyte‐film/nanoparticle patterns by using a plasma etching technique to form, first, a patterned self‐assembled monolayer surface, followed by layer‐by‐layer assembly of polyelectrolyte‐films/nanoparticles. Octadecyltrimethoxysilane (ODS) and (3‐aminopropyl)triethoxysilane (APTES) self‐assembled monolayers (SAMs) were used for polyelectrolyte‐film and nanoparticle patterning, respectively. The resolution of the proposed patterning method can easily reach approximately 2.5 μm. The height of the groove structure was tunable from approximately 2.5 to 150 nm. The suspended lipid membrane across the grooves was fabricated by incubating the patterned polyelectrolyte groove arrays in solutions of 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine (DOPC) giant unilamellar vesicles (GUVs). The method demonstrated here reveals a new path to create patterned 2D or 3D structures.     

Superelastic,Macroporous Polystyrene‐Mediated Graphene Aerogels for Active Pressure Sensing

Three‐dimensional (3D) graphene‐based polymer/graphene aerogels with excellent mechanical properties are crucial for broad applications. The creation of such polymer/graphene aerogels remains challenging because of the poor dispersion and compatibility of polymer within the graphene matrix. By using the freezing‐directed assembly of graphene under the assistance of surfactant, 3D macroporous polystyrene/graphene aerogels (MPS‐GAs) with lightweight, superelastivity (80 % strain), high strength (80 kPa), and good electrical properties have been achieved in this study. The as‐prepared MPS‐GAs shows excellent electromechanical performance with stable cyclic resilient properties and sensitive resistance responses, thus making the MPS‐GAs promising candidates for applications in actuators, elastic conductors, strain/pressure sensors, and wearable devices.     

A pH-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration

We present here a p H-responsive activatable aptamer probe for targeted cancer imaging based on i-motif-driven conformation alteration. This p H-responsive activatable aptamer probe is composed of two single-stranded DNA. One was used for target recognition, containing a central, target specific aptamer sequence at the 3′-end and an extension sequence at the 5′-end with 5-carboxytetramethylrhodamine(TAMRA) label(denoted as strand A). The other(strand I), being competent to work on the formation of i-motif structure, contained four stretches of the cytosine(C) rich domain and was labeled with a Black Hole Quencher 2(BHQ2) at the 3′-end. At neutral or slightly alkaline p H, strand I was hybridized to the extension sequence of strand A to form a double-stranded DNA probe, termed i-motif-based activatable aptamer probe(I-AAP). Because of proximityinduced energy transfer, the I-AAP was in a "signal off" state. The slightly acidic p H enforced the strand I to form an intramolecular i-motif and then initiated the dehybridization of I-AAP, leading to fluorescence readout in the target recognition. As a demonstration, AS1411 aptamer was used for MCF-7 cells imaging. It was displayed that the I-AAP could be carried out for target cancer cells imaging after being activated in slightly acidic environment. The applicability of I-AAP for tumor tissues imaging has been also investigated by using the isolated MCF-7 tumor tissues. These results implied the I-AAP strategy is promising as a novel approach for cancer imaging.     

Antifungal activity of some diaryl ethers

Several diaryl ethers were synthesized and tested in vitro against seven phytopathogenic fungi, namely Fusarium graminearum, Alternaria alternate, Helminthosporium sorokinianum, Pyricularia oryzae, Fusarium oxysporum f. sp. vasinfectum, Fusarium oxysporum f. sp. cucumarinum and Alternaria brassicae. Compared to a commercial agricultural fungicide, hymexazol, especially compounds a, b, e, g and k were found to be more effective at 50 mug/ml against F. graminearum, F. oxysporum f. sp. vasinfectum and F. oxysporum f. sp. cucumarinum. Meantime, some structure-activity relationships were also observed.