A homogeneous chitosan–ferrocene/graphene oxide/glucose oxidase (CS–Fc/GO/GOx) nanocomposite film was successfully constructed as a novel platform for the fabrication of glucose biosensor. The ...morphologies and electrochemistry of the nanocomposite film were investigated by using scanning electron microscopy and electrochemical techniques including electrochemical impedance spectroscopy and cyclic voltammetry, respectively. Results demonstrated that the uniformly dispersed GO within the CS matrix could significantly improve the stability of GO and make it exhibit a positive charge, which was more favorable for the further immobilization of biomolecules, such as GOx, with higher loading. Further attaching redox mediator ferrocene group (Fc) to CS could not only effectively prevent the leakage of Fc from the matrix and retain its electrochemical activity, but also improve the electrical conductivity of CS and promote the electron-transfer between GOx and electrode. Biosensors based on this CS–Fc/GO/GOx film had advantages of fast response, excellent reproducibility, high stability, and showed a linear response to glucose in the concentration range from 0.02 to 6.78
mM with a detection limit of 7.6
μM at a signal-to-noise ratio of 3 and exhibited a higher sensitivity of 10
μA
mM
−1
cm
−2. The proposed strategy based on CS–Fc/GO nanocomposite for the immobilization of enzymes can be of practical relevance for the facile design of biosensors, as well as for the construction of new multifunctional bioelectrochemical systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We design two artificial substrate peptides to synthesize blue-emissive Cu nanoclusters and red-emissive Au nanoclusters, respectively. In addition to the biomineralization function, these two ...peptides retain the biological activity to be phosphorylated by protein kinase and digested by carboxypeptidase Y. In the absence of protein kinase, the peptides capped on the nanoclusters suffer consecutive exocleavage by carboxypeptidase Y, resulting in oxidation and thus fluorescence quenching of the nanoclusters due to the losing of peptide protection. In the presence of protein kinase A and casein kinase II, the phosphorylation modification on corresponding substrate peptides protects the peptides against carboxypeptidase Y digestion and then the fluorescence of the nanoclusters can be retained. Since a single excitation wavelength can excite the both nanoclusters, blue and red emissive signals can be collected at the same time and then the quantitative determination of protein kinase A and casein kinase II can be achieved simultaneously.
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A facile and green approach has been developed for synthesis of boron nitride quantum dots (BNQDs). The obtained BNQDs exhibit strong fluorescence and excellent stabilities, including high ...thermostability, good salt tolerance stability, pH-independence ability, and excellent antiphotobleaching capability. The strong inner filter effect between 2,4,6-trinitrophenol (TNP) and BNQDs resulted in fluorescence quenching of BNQDs. Thus, TNP can be selectively and sensitively detected in the concentration range of 0.25–200 μM, with a limit detection of 0.14 μM. The BNQD-based turn-off sensor shows potential prospects for rapidly and selectively detecting TNP in natural water samples without tedious sample pretreatment processes.
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Systematic dissection of the ubiquitylation proteome is emerging as an appealing but challenging research topic because of the significant roles ubiquitylation play not only in protein degradation ...but also in many other cellular functions. High-throughput experimental studies using mass spectrometry have identified many ubiquitylation sites, primarily from eukaryotes. However, the vast majority of ubiquitylation sites remain undiscovered, even in well-studied systems. Because mass spectrometry-based experimental approaches for identifying ubiquitylation events are costly, time-consuming and biased toward abundant proteins and proteotypic peptides, in silico prediction of ubiquitylation sites is a potentially useful alternative strategy for whole proteome annotation. Because of various limitations, current ubiquitylation site prediction tools were not well designed to comprehensively assess proteomes.
We present a novel tool known as UbiProber, specifically designed for large-scale predictions of both general and species-specific ubiquitylation sites. We collected proteomics data for ubiquitylation from multiple species from several reliable sources and used them to train prediction models by a comprehensive machine-learning approach that integrates the information from key positions and key amino acid residues. Cross-validation tests reveal that UbiProber achieves some improvement over existing tools in predicting species-specific ubiquitylation sites. Moreover, independent tests show that UbiProber improves the areas under receiver operating characteristic curves by ~15% by using the Combined model.
The UbiProber server is freely available on the web at http://bioinfo.ncu.edu.cn/UbiProber.aspx. The software system of UbiProber can be downloaded at the same site.
Supplementary data are available at Bioinformatics online.
Electrochemical nitrogen fixation techniques have emerged as a promisingly sustainable approach to face the challenge associated with nitrogen activation of ammonia synthesis by the Haber–Bosch ...process under ambient conditions. Herein, the performance of electrocatalytic nitrogen reduction for the production of α‐Fe2O3 nanospindles coated with mesoporous TiO2 with different crystallinity denoted as α‐Fe2O3@mTiO2‐X (X=300, 400, and 500 °C) were investigated. The as‐prepared α‐Fe2O3@mTiO2‐400 composite exhibits a large NH3 yield (27.2 μg h−1 mgcat.−1) at −0. 5 V vs. the reversible hydrogen electrode and a high Faradaic efficiency (13.3 %) in 0.1 m Na2SO4, with excellent electrochemical durability. This work presents a novel avenue for the rational design of efficient unique hetero‐phase nanocatalysts toward sustainable electrocatalytic N2 fixation.
Quick fix: Amorphous/crystalline hetero‐phase TiO2 coated α‐Fe2O3 core–shell nanospindles are identified as electrocatalysts for effective artificial N2 fixation to NH3 under ambient conditions. In 0.1 m Na2SO4, this electrocatalyst achieves a high NH3 yield of 27.2 μg h−1 mgcat.−1 with a Faradaic efficiency of 13.3 % at −0.5 V, outperforming most reported aqueous‐ and iron‐based N2 reduction electrocatalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Mercury ions (Hg2+) and lead ions (Pb2+) are two of the most toxic heavy metal ions; thus, the efficient and effective removal of them is of great significance. Herein, a one-pot synthesis protocol ...has been proposed to synthesize boron carbon nitride nanosheets (BCN NSs) via the pyrolysis of the mixture of melamine and boric acid. To optimize the synthesis conditions, a series of products were made by varying the molar ratio and heating temperature. Finally, the BCN NSs obtained from the mixture of melamine and boric acid with the molar ratio of 3:3 at 550 °C was selected for the best Hg2+ and Pb2+ removal efficiency. Due to the successfully introduction of abundant function groups, enhanced specific surface area and hydrophilicity and electrostatic attraction ability, BCN NSs exhibit excellent adsorption performance toward Hg2+ and Pb2+ with the maximum adsorption capacity of 625.0 and 210.97 mg g–1, respectively. The sorption isotherms fit well with the Langmuir adsorption model which suggest the monolayer adsorption behavior, and the pseudo-second-order kinetic adsorption processes indicate the chemisorption mechanism. Besides, BCN NSs show excellent chemical stability, and the adsorption capacities remain more than 90% even after 6 adsorption/desorption cycles. By virtue of the cost-effective and facile production methodology, combined with the excellent absorption performance, the BCN NSs show great potential for practical application in the field of wastewater purification.
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In this work, we synthesized a two-dimensional fluorescent covalent–organic framework (TFPB–TTA COF) nanosheet by selecting and designing reactive monomers to realize the dual-functional processing ...of nitrophenols. The staggered benzene ring, triazine structure, and imine bond (CN) of the TFPB–TTA COF can capture free nitrophenols through hydrogen bonding and conjugation interaction, and then, the photoinduced electron transfer and fluorescence resonance energy transfer (FRET) between the TFPB–TTA COF and nitrophenols affects the fluorescence emission of the TFPB–TTA COF, realizing the fluorescence sensing of nitrophenols. The large K sv values and the low detection limit suggest that the TFPB–TTA COF can serve as sensitive and selective fluorescence sensors for nitrophenol detection in an aqueous system. At the same time, the strong interaction combined with the porous network structure of the TFPB–TTA COF facilitates the efficient adsorption and removal of nitrophenols. Especially for 2,4,6-trinitrophenol, the maximum adsorption capacity can reach 1045.53 mg/g with good recyclability and high structural stability of the TFPB–TTA COF. This work proposed a simple synthetic method for the construction of a fluorescent COF platform for the sensitive determination and efficient adsorption of nitrophenols.
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A simple and sensitive photoluminescence (PL) assay for the activity of a protein kinase based on the selective aggregation of phosphorylated peptide–graphene quantum dot (GQD) conjugates triggered ...by Zr4+ ion coordination has been established. With more sophisticated design of the peptide substrate sequences, detecting other enzymes could also be possible. Under optimal conditions, a linear relationship between the decreased PL intensity of peptide–GQD conjugates and the concentration of casein kinase II (CK2) in the range from 0.1 to 1.0 unit mL–1 with a detection limit of 0.03 unit mL–1 (3σ) was obtained. The EC50 value (i.e., the enzyme concentration producing 50% substrate conversion) for CK2 was evaluated to be 0.34 unit mL–1. The proposed method showed potential applications in kinase inhibitor screening. To demonstrate the potential of this GQD-based platform for screening of kinase inhibitors in real biological systems, the inhibition of CK2 phosphorylation activity by four different inhibitors (ellagic acid, 5,6-dichlorobenzimidazole-l-β-d-ribofuranoside, emodin, and quercetin) was tested in human serum by comparing signals from samples incubated with the inhibitors against that without any inhibitor. As expected, in the presence of inhibitors, the PL intensity increased with increasing inhibitor efficiency. The IC50 value (inhibitor concentration producing 50% inhibition) for ellagic acid was estimated to be 0.041 μM. The developed protocol provides a new and promising tool for the analysis of both the enzyme and its inhibitors with low cost and excellent performance.
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Copper is a highly toxic environmental pollutant with bioaccumulative properties. Therefore, sensitive detection of Cu2+ is very important to prevent over-ingestion, and visual detection is preferred ...for practical applications. In this work, we developed a simple and environmental friendly approach to synthesize hyperbranched polyethyleneimine-protected copper nanoclusters (hPEI-Cu NCs) with great stability against extreme pH, high ionic strength, thiols etching and light illumination, which were then conjugated to the surface of silica coated CdSe quantum dots (QDs) to design a ratiometric fluorescence probe. In the presence of different amounts of Cu2+ ions, the fluorescence of Cu NCs can be drastically quenched, while the emission from QDs stayed constant to serve as a reference signal and the color of the probe changed from yellow-green to red, resulting in ratiometric and visualization detection of Cu2+ ion with high accuracy. The detection limit for Cu2+ was estimated to be 8.9 nM, much lower than the allowable level of Cu2+ in drinking water (∼20 μM) set by U.S. Environmental Protection Agency. Additionally, this probe can be also applied for the determination of Cu2+ ion in complex real water samples.
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•We developed a ratiometric fluorescence probe for ratiometric and visualization detection of copper ions.•Copper nanoclusters was conjugated to silica coated CdSe quantum dots to design a ratiometric fluorescence probe.•Highly sensitive and visualized detection of Cu2+ was achieved.•This method provided a built-in correction for environmental interference.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abstract Extracting uranium from real water samples remains a great challenge due to low uranium concentration, concentrated competing ions and volumes of water. The design and preparation of uranium ...adsorbents with high efficiency and affinity are still difficult. Herein, we presented a facile one‐pot strategy to obtain a novel metal organic framework (denoted as Mn‐NDISA) for stable and efficient trapping of low concentration uranium. Mn‐NDISA with a built‐in hydrophobic cavity can boost the absorption affinity to 1.99 × 10 6 mL g −1 through the cooperative capture composed of electrostatic interaction, coordination force and hydrogen binding. Owing to the coordination‐available oxygen sites in flexible framework, a rapid kinetic equilibrium was achieved in just 25 min. Moreover, these exceptional adsorption features enabled Mn‐NDISA to successfully capture the naturally occurring uranium traces (~ppb) in wastewater samples, making it one of the most influential absorbents toward UO 2 2+ ever reported. The experimental and theoretical studies revealed that the electrostatic attraction came from the surface negatively charged Mn‐NDISA and the positively charged UO 2 2+ . The coordination originated from Lewis basic hydroxyl, carbonyl groups, and Lewis acid UO 2 2+ , while hydrogen bonds further reinforced the as‐formed uranium binding complex. This research offered a promising cooperative capture strategy to improve the uranium affinity of the pristine MOF for trace contaminants removal in environmental remediation fields.
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