A Peptoid-like Approach Led to Lactam-Lactam Dimer Formation in 2-Hydroxy-N-alkyl-N-phenyl-nicotinamides and Their Polymorphism and Solvatomorphism.

Four 2-hydroxy-N-alkyl-N-phenyl-nicotinamides (1-4) were synthesized, and their crystal structures were analyzed to investigate the effect of substitution on their crystal packing of N-phenyl-2-hydroxynicotinanilides. In these compounds, substituents were introduced on the amide N, leading to a peptoid-like structure. One solvent-free form and two hydrates were harvested for compound 1, and one anhydrous form and one hydrate were obtained for compound 2. Polymorphism was observed in compounds 3 and 4. The molecules were found to be in the keto form rather than the enol tautomer. Because of steric effects, the molecules took on an E configuration, leading to a hairpin-like geometry. A lactam-lactam dimer synthon was formed in all solvent-free structures, and a tetramer motif was observed for the first time. Dehydration of the two hydrates of 1 and the hydrate of 2 led to their respective solvent-free form. Phase transition between the polymorphs was revealed in compound 3. Theoretical calculations, including conformational energy evaluation, hydrate forming propensity assessment, and lattice energy appraisal, were performed to provide a reasonable explanation for the keto tautomer and the formation of the hydrates of compound 1.

Species diversity of coral reef fishes around the West Island of Sanya City, South China Sea, based on environmental DNA.

Background: West Island is the second largest island in the Hainan Province, China and its surrounding sea area has a well-preserved coral reef ecosystem and high species diversity of coral reef fishes. Undoubtedly, coral reef fishes and coral reefs have complex symbiotic relationships and fish species diversity should reflect the healthy status of coral reef ecosystems. Environmental DNA (eDNA) is a useful and sensitive tool to detect fish species and causes less environmental damage than traditional fish survey methods. This paper investigated coral reef fish species of West Island, Hainan Province, China, based on eDNA and provided scientific data for understanding and protection of the coral reef ecosystem of the South China Sea. New information: The sea area surrounding West Island is the most important component of the coral reef ecosystem in the northern part of the South China Sea, which is also an essential part of the largest National Coral Reef Reserve in China. However, complete data of fish species distributed in this region have been a long-term gap. This study provides information on 41 fish species belonging to 28 genera, 16 families and three orders in this sea area and is the first complete record of coral reef fishes surrounding the West Island. In addition, the information of Molecular Operational Taxonomic Units (MOTUs) for taxon identification were also provided and it could contribute to building specific eDNA taxonomy database of coral reef fishes of the South China Sea. The study includes three datasets, with aspects of fish taxon-occurrences, MOTUs sequences and information of environmental indicators surrounding West Island, Hainan Province, China. The "fish taxon occurrences" dataset presents records involving taxonomic, distribution, habitat condition, latitude and longitude of 41 coral reef fish species detected, based on eDNA, the "MOTUs sequences" dataset provides MOTUs sequences and their abundance of 31 species detected and the "information of environmental indicators" dataset presents records of transparency, temperature, water pressure, dissolved oxygen, electrical conductivity, hydrogen and redox potential measured from five sampling localities.

Feature-Based Diversity Optimization for Problem Instance Classification.

Understanding the behaviour of heuristic search methods is a challenge. This even holds for simple local search methods such as 2-OPT for the Travelling Salesperson Problem (TSP). In this article, we present a general framework that is able to construct a diverse set of instances which are hard or easy for a given search heuristic. Such a diverse set is obtained by using an evolutionary algorithm for constructing hard or easy instances which are diverse with respect to different features of the underlying problem. Examining the constructed instance sets, we show that many combinations of two or three features give a good classification of the TSP instances in terms of whether they are hard to be solved by 2-OPT.

Reversible luminescent humidity chromism of organic-inorganic hybrid PEA2MnBr4 single crystals.

Organic-inorganic hybrids have drawn great attention for gas sensors due to their high sensitivity, good selectivity and acceptable stability at room temperature. There are two main approaches by which organic-inorganic hybrids convert gas information to electric or optical signals (vapochromism). Here, we have reported a new organic-inorganic hybrid PEA2MnBr4 for humidity detection by luminescent visible chromism. PEA2MnBr4 single crystals were grown by the solution method and determined by single-crystal X-ray diffraction. Luminescent humidity chromism was found on PEA2MnBr4 from green emission at the water-desorption state to pink emission at the water-adsorption state within 18 s at a relative humidity of 38% RH. This obviously visible chromism was further used to check the water content in toluene with a low detection limit between 0.02 and 0.05 vol%.

All-Inorganic Copper Halide as a Stable and Self-Absorption-Free X-ray Scintillator.

Lead halide perovskites have recently shown great potential as X-ray scintillators; however, the toxicity of the lead element seriously restricts their applications. Herein we report a new lead-free and self-absorption-free scintillator based on Rb2CuCl3 metal halide. The Rb2CuCl3 exhibits a near-unity photoluminescence quantum yield (99.4%) as well as a long photoluminescence lifetime (11.3 µs). Furthermore, Rb2CuCl3 demonstrates an appreciable light yield of 16 600 photons per megaelectronvolt and a large scintillation response with a linear range from 48.6 nGyair s-1 to 15.7 µGyair s-1. Notably, the detection limit is as low as 88.5 nGyair s-1, enabling a reduced radiation dose to the human body when a medical and security check is conducted. In addition, Rb2CuCl3 exhibits good stability against the atmosphere, continuous ultraviolet light, as well as X-ray irradiation. The combination of the decent scintillation performance, low toxicity and good stability suggests the Rb2CuCl3 could be a possible promising X-ray scintillator.

An assessment of the interaction for three Chrysanthemum indicum flavonoids and α-amylase by surface plasmon resonance.

This study evaluated the interaction of Chrysanthemum indicum (CI) flavonoids (luteolin, acacetin, and buddleoside) with α-amylase. Surface plasmon resonance (SPR) assay showed their equilibrium dissociation constants (KD ) are 1.9695 ± 0.12, 2.9240 ± 0.20, and 3.2966 ± 0.08 mM at pH 6.0, respectively. Furthermore, their binding affinities were influenced by KCl, MgCl2, and CaCl2. Enzymatic kinetic studies revealed that three flavonoids exhibited noncompetitive α-amylase inhibitory activity. The inhibitory sequence is luteolin > acacetin > buddleoside, which was in accordance with the results of binding affinity from SPR. 1,1-diphenyl-2-picryl hydrazyl radical assay demonstrated that antioxidant activities of three flavonoids were inhibited significantly with α-amylase. Meanwhile, the study reveals that hydroxyl on C'-4, C'-5, and C-7 of flavonoids play an important role on the interaction of three flavonoids with α-amylase. Also, SPR could be used as sensor for rapid screening inhibitors of α-amylase and provide useful information for the application of C. indicum flavonoids in food and pharmaceutical area.

A highly sensitive tetracycline sensor based on a combination of magnetic molecularly imprinted polymer nanoparticles and surface plasmon resonance detection.

A method is reported for in-situ detection of the antibiotic tetracycline (TC). It is based on a combination of extraction of TC by magnetic molecularly imprinted polymers nanoparticles (MMIPs NPs) and detection by surface plasmon resonance (SPR). The TC-captured MMIPs NPs were flowed over the surface of the SPR chip that was modified with mercaptoethylamine. The SPR signal undergoes a strong increase through the use of MMIPs NPs. It increases linearly in the 5.0-100 pg·mL-1 TC concentration range, and the detection limit is as low as 1.0 pg·mL-1 (at S/N = 3). This method shows selectivity to TC compared with structurally analogues. In order to demonstrate the power of the method, it was applied to the analysis of milk spiked with TC. These results were validated by comparing them to those of an enzyme-linked immunoassay. The average recovery is in the range of 95.7-104.6%. Graphical abstract Schematic representation of a surface plasmon resonance assay for the sensitive determination of tetracycline in milk using the magnetic molecularly imprinted polymers nanoparticles that can extract tetracycline and amplify the SPR signal.

Circularly polarized light detection using chiral hybrid perovskite.

Circularly polarized light (CPL) detection is required in various fields such as drug screening, security surveillance and quantum optics. Conventionally, CPL photodetector needs the installation of optical elements, imposing difficulties for integrated and flexible devices. The established CPL detectors without optical elements rely on chiral organic semiconductor and metal metamaterials, but they suffer from extremely low responsivity. Organic-inorganic hybrid materials combine CPL-sensitive absorption induced by chiral organics and efficient charge transport of inorganic frameworks, providing an option for direct CPL detection. Here we report the CPL detector using chiral organic-inorganic hybrid perovskites, and obtain a device with responsivity of 797 mA W-1, detectivity of 7.1 × 1011 Jones, 3-dB frequency of 150 Hz and one-month stability, a competitive combined feature for circularly polarized light detection. Thanks to the solution processing, we further demonstrate flexible devices on polyethylene terephthalate substrate with comparable performance.

Strategical isolation of efficient chicken feather-degrading bacterial strains from tea plantation soil sample.

Chicken feather waste is generally insufficiently utilized despite its high content of protein, constituting an environmental issue. Biodegradation of the waste with enabling microbes provides an advantageous option among the available solutions. In this study, an efficient whole feather-degrading strain was strategically isolated from a soil sample taken from a local tea plantation that has little or nothing to do with feathers. The strain was identified as Bacillus thuringiensis (designated as FDB-10) according to the cloned complete 16S rRNA sequence. The FDB-10 could efficiently degrade briefly heat-treated whole feather (102 °C, 5 min; up to 90% of a maximum concentration of 30 g/L) in a salt medium supplemented with 0.1 g/L yeast extract within 24 h (37 °C, 150 rpm). Addition of carbon sources (glycerol, glucose, starch, Tween 20, Tween 80, 1.25 g/L as glycerol) to the fermentation medium could improve the degradation. However, significant inhibition could be observed when the added carbon source reached the amount usually adopted in the investigation of carbon source preference (1%). Nitrogen source (NH4Cl, (NH4)2SO4, peptone) adversely influenced the performance of the strain. When the molar concentrations of NH4+ were equal for the two salt, the inhibitory effect on degradation of whole feathers was similar. Entirely different from other reported feather-degrading strains showing a preference to melanin-free feather substrates, the strain isolated in this study could degrade melanin-containing feather equally efficiently, and higher protease activity could be detected in the digest mix. As a plus, the strain could degrade feathers in rice wash produced in daily cooking, indicating its potential use in the simultaneous treatment of rice cooker wastewater produced by a rice processing plant. All these results imply that the FDB-10 is a strain with great potential in the biodegradation of feather waste.

Surface Passivation of Bismuth-Based Perovskite Variant Quantum Dots To Achieve Efficient Blue Emission.

Metal halide perovskite quantum dots (QDs) recently have attracted great research attentions. However, blue-emitting perovskite QDs generally suffer from low photoluminescence quantum yield (PLQY) because of easily formed defects and insufficient surface passivation. Replacement of lead with low toxicity elements is also preferred toward potential commercial applications. Here, we apply Cl-passivation to boost the PLQY of MA3Bi2Br9 QDs to 54.1% at the wavelength of 422 nm, a new PLQY record for blue emissive, lead-free perovskite QDs. Because of the incompatible crystal structures between MA3Bi2Br9 and MA3Bi2Cl9 and the careful kinetic control during the synthesis, Cl- anions are engineered to mainly locate on the surface of QDs acting as passivating ligands, which effectively suppress surface defects and enhance the PLQY. Our results highlight the potential of MA3Bi2Br9 QDs for applications of phosphors, scintillators, and light-emitting diodes.

Investigation of the interaction for three Citrus flavonoids and α-amylase by surface plasmon resonance.

Flavonoids, a class of natural drugs with broad biological activity, exhibit inhibitory effect on α-amylase. Citrus peel is a good source of flavonoids. The real-time interactions between three Citrus flavonoids (naringin, neohesperidin, hesperidin) and α-amylase were investigated by surface plasmon resonance biosensor, and were compared with the α-amylase inhibitors, acarbose. These results showed the binding affinities of naringin, neohesperidin and hesperidin with α-amylase reach the highest at pH6 with KD values of 2.27±0.18mM, 3.09±0.20mM and 3.51±0.09mM, and can be reinforced with 0.2M NaCl and 0.1M CaCl2, respectively. The results of 1, 1-diphenyl-2-picryl hydrazyl radical assay indicate that the antioxidant activities of naringin, neohesperidin and hesperidin are significantly inhibited by interacting with α-amylase, and the inhibition percentage are 47.61±0.034%, 22.81±0.037% and 21.01±0.051%, respectively. Additionally, it is found that both the number and the position of hydroxyl group play an important role in the interaction of three Citrus flavonoids and α-amylase. These results provide useful information for rapid screening inhibitors of α-amylase from plant-based food.