Effect of Different Carbon Sources on Antioxidant Properties of Exopolysaccharides Produced by Scleroderma areolatum (Agaricomycetes).

Five kinds of exopolysaccharides (EPS) were obtained by fermentation of Scleroderma areolatum Ehrenb. with sucrose, glucose, maltose, lactose, and fructose as carbon sources. Antioxidant abilities of the obtained EPSs were evaluated by inhibiting AAPH, HO·, and glutathione (GS·) induced oxidation of DNA and quenching 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS· and galvinoxyl radicals. The effects of carbon sources on the antioxidant properties of EPSs could be examined. The results showed that five EPSs can effectively inhibit radicals induced oxidation of DNA, and the thiobarbituric acid reactive substances (TBARS) percentages were 44.7%-80.8%, 52.3%-77.5%, and 44.7%-73.3% in inhibiting AAPH, HO·, and GS· induced oxidation of DNA, respectively. All five EPSs could scavenge ABTS· and galvinoxyh, and exhibit superior activity in scavenging free radicals. Antioxidant abilities of EPS with fructose as carbon source were highest among five EPS.

An improved sample container cup and its effect on NIRS of tobacco smoke for quality stability estimation.

This paper describes a design of an improved self-made Bruker NIR cup and analyzes the effect of the equipment modification to fit the Cambridge filter pad, which enhances experimental efficiency and reduces operational complexity. A self-made NIR cup based on the classical NIR cup is designed to speed up the operation process and reduce the experiment's time cost. To estimate the effect of this equipment modification, the NIR spectra from the classical sample cup and the new self-made cup are compared and analyzed. Furthermore, the quality evaluation results from NIR data of the two cups are also compared according to a distance metric chemometrics method, which shows quality analytical values between these two cups are approaching each other while the experiment efficiency is improved.•This paper introduces a newdesign of a self-made container cup improved from the Bruker's traditional sample container cup to better fit the filter pad and improve the experiment efficiency and convenience.•This paper also analyzes the effect of this container cup change by comparing the NIR spectra before and after modification.

Visible light-induced direct alkylation of the purine C8-H bond with ethers.

The one-step visible light-induced direct alkylation of the C8-H bond for purine derivatives by ethers was developed using Eosin Y as the photocatalyst and t-BuOOH as the oxidant at room temperature. This method describes the coupling of the α-C of the ether to the C8 of purine. Of particular interest is that substrates include purines with various functional groups and even unprotected 9H-purines. The protocol provides an effective method for the synthesis of 8-alkylpurine derivatives with high atom economy and high regioselectivity.

One-Step Visible Light Photoredox-Catalyzed Purine C8 Alkoxylation with Alcohol.

A cross-dehydrogenation coupling reaction between purines and alcohols, induced by visible light, using an acridinium photocatalyst and air as the sole oxidant, to synthesize a series of C8-alkoxy purine derivatives was developed. This protocol is a green and novel method to construct the C8-O bond on a purine ring with high step and atom economy.

A T-rich nucleic acid-enhanced electrochemical platform based on electroactive silver nanoclusters for miRNA detection.

DNA-templated silver nanoclusters (DNA/AgNCs) serve as a useful electrochemical sensing nanomaterial characterized by excellent electroactivity and good stability, while the effect of surrounding nucleotides on their electroactivity has not been studied. Herein, we validated a nucleotide-assisted enhancement mechanism of the DNA/AgNCs electroactivity caused by T-rich nucleic acid sequences in the vicinity of AgNCs. Based on the T-rich nucleic acid-enhanced AgNCs (NAE-AgNCs) combined with hybrid chain reaction (HCR), a novel signal-enhanced electrochemical biosensing platform was established for the ultrasensitive detection of miRNA. In the presence of target miRNA-155, HCR could be triggered to generate duplex strands containing both numerous AgNC synthesis sites and T-rich overhang strands upon the electrode. With the electrodeposition of adjacent AgNCs on the electrode, the larger oxidation potential of T-rich nucleic acid leaded to stronger electron-accepting capacity, which could contribute to increased current responses. The T-rich NAE HCR electrochemical strategy resulted in a detection limit of 0.39 fM for miRNA-155 detection, one order of magnitude lower than conventional HCR-based electrochemical sensors. This T-rich nucleic acid-assisted enhancement mechanism provided a new direction to construct highly sensitive, label-free, low-cost, and simple sensing platforms for applications in biomarker assays and clinic diagnosis.

Construction of a Polarity-Switchable Photoelectrochemical Biosensor for Ultrasensitive Detection of miRNA-141.

As an early-stage tumor biomarker, microRNA (miRNA) has clinical application potential and its sensitive and accurate detection is significant for early tumor diagnosis. In this study, a photoelectrochemical (PEC) biosensing platform was fabricated for ultrasensitive miRNA-141 detection, which is based on a photocurrent polarity-switchable system using CdS quantum dots (QDs) in the presence of a 5,10,15,20-tetrakis (4-aminophenyl)-21H,23H-porphine (Tph-2H)-coated glassy carbon electrode (GCE). As an excellent photoactive material, Tph-2H has a narrow band gap that effectively gathers photoelectrons under visible light irradiation and improves the transfer ability of photogenerated electrons. Further, the detection sensitivity of miRNA-141 could be significantly improved by combining an enzyme-assisted recycle amplification reaction and a magnetic bead-based separation strategy. The proposed photocurrent polarity-switchable PEC biosensor could efficiently eliminate the false-positive or false-negative signals and achieve a wide linear response range from 1 fM to 1 nM with a low detection limit of 0.33 fM for miRNA-141, providing a potentially alternative solution for detecting other biomarkers in bioanalysis and clinical diagnosis.

Mahalanobis distance based similarity regression learning of NIRS for quality assurance of tobacco product with different variable selection methods.

Quality assurance is one of the key issues in tobacco industry and many efforts have been put on the quality control. This paper introduces a new chemometrics technique to estimate the "quality similarity rate", which is used for quality control. The value of the quality similarity rate represents the similarity degree between the products and the standard reference samples, which is a global parameter that can be generated by either human assessors or machine learning. Supervised similarity regression models are built to automatically estimate the quality similarity rate value from NIRS data of tobacco leaf and smoke. For the similarity regression learning, the metric matrix is generated by a novel method which calculates the Mahalanobis distance from the segmented near infrared spectroscopy (NIRS). The results show the similarity regression learning can predict the quality similarity score well in high speed and can be improved with lasso (least absolute shrinkage and selection operator) related feature selection algorithms such as sRDA (sparse redundancy analysis) and glmnet.

A trimeric tri-Tb3+ including antimonotungstate and its Eu3+/Tb3+/Dy3+/Gd3+-codoped species with luminescence properties.

A trimeric tri-Tb3+-including antimonotungstate (AMT) hybrid Na17{(WO4)[Tb(H2O)(Ac)(B-α-SbW9O31(OH)2)]3}·50H2O (Tb3W28) was successfully synthesized, in which the capped tetrahedral {WO4} group plays a significant template role in directing the aggregation of three [B-α-SbW9O33]9- fragments and three Tb3+ ions. Eu3+/Tb3+/Dy3+/Gd3+-codoped AMT materials based on Tb3W28 were firstly prepared and their luminescence properties were investigated. The red emitter Eu3+, yellow emitter Dy3+, and nonluminous Gd3+ ions were codoped into Tb3W28 to substitute Tb3+ ions for investigating the energy transfer (ET) mechanism among Eu3+, Tb3+, and Dy3+ ions. Upon the 6H15/2 → 4I13/2 excitation at 389 nm of the Dy3+ ion, the ET1 mechanism (Dy3+ → Tb3+) was confirmed as a non-radiative dipole-dipole interaction. Under the 7F6 → 5L10 excitation at 370 nm of the Tb3+ ion, the ET2 mechanism (Tb3+ → Eu3+) was identified as a non-radiative quadrupole-quadrupole interaction. Under excitation at 389 nm, the two-step successive Dy3+ → Tb3+ → Eu3+ ET3 process was proved in Dy1.2Tb3zEu0.03Gd1.77-3zW28. Through changing the excitation wavelengths, the emission color of Dy1.2Tb1.2Eu0.03Gd0.57W28 can vary from blue to yellow, in which a near-white-light emission case was observed upon excitation at 378 nm. This work not only provides a systematic ET mechanism study of hetero-Ln-codoped AMTs, but also offers some useful guidance for designing novel performance-oriented Ln-codoped polyoxometalate-based materials.

Acetate-Decorated Tri-Ln(III)-Containing Antimonotungstates with a Tetrahedral {WO4} Group as a Structure-Directing Template and Their Luminescence Properties.

Four acetate-decorated tri-Ln-substituted trimeric antimonotungstates (AMTs) Na17{(WO4)[Ln(H2O)(Ac)(B-α-SbW9O31(OH)2)]3}·50H2O [Ln = Eu3+ (1), Dy3+ (2), Ho3+ (3), or Gd3+ (4)] were isolated by reaction of Na9[B-α-SbW9O33]·19.5H2O, Na2WO4·2H2O, and Ln(NO3)·6H2O in a HAc/NaAc buffer solution. Interestingly, a tetrahedral {WO4} group plays a significant structure-directing template role in the formation of their polyoxoanions. With regard to luminescence properties, with a change in the excitation wavelength, it is available to switch emission colors from orange to red for 1, blue to green for 2, and blue to yellow for 3. Under the O → W LMCT excitation, energy transfer from AMT fragments to Eu3+, Dy3+, and Ho3+ ions occurs because Ln3+ ions can absorb energy from O → W LMCT emission of AMT segments. The temperature-dependent luminescence behaviors (25-720 °C) of 1 together with auxiliary emitting photographs illustrate that the growing emission in the temperature range of 25-100 °C results from the loss of lattice water molecules, the decline of emission between 100 and 320 °C may occur because crystals become amorphous powders, the slow emission decay (220-320 °C) is due to the case that the emission enhancement derived from the removal of water ligands on Eu3+ ions in some degree compensates for the decline of emission intensity, the sharp decrease in emission (320-520 °C) may result from the change in the coordinate environment of Eu3+ ions, and the weak recovery of emission (620-720 °C) may be ascribed to the formation of new phase Na0.5Eu0.5WO4. This work lays a significant foundation for preparing novel POM-based luminescent materials.