Rational design of an iminocoumarin-based fluorescence probe for peroxynitrite with high signal-to-noise ratio.

As a high reactive oxygen species (ROS) and a reactive nitrogen species (RNS), peroxynitrite anion (ONOO- ) is widely present in organisms and plays influential roles in physiological and pathological processes. It is of great significance to develop effective fluorescent probes for imaging peroxynitrite variation in living systems. Herein we present a novel fluorescent probe TQC0 for monitoring ONOO- based on the iminocoumarin platform, and this probe was synthesized by the knoevenagel condensation between a dihydropyridine-salicylaldehyde derivative and 2-benzothiazole-acetonitrile, and subsequently masked with the boronate moiety. The obtained probe TQC0 exhibited a high signal-to-noise ratio (206-fold) and a quick 'turn-on' response (about 10 min) with great selectivity and sensitivity. Furthermore, the probe TQC0 was successfully applied for imaging ONOO- in living cells with low cytotoxicity.

Effects of Low Concentration Benzophenone-3 Exposure on the Sex Ratio and Offspring Development of Zebrafish (Danio rerio).

Benzophenone-3 (BP-3) is an important ultraviolet (UV)-screening agent using in cosmetics, however, the associated environmental pollution and the toxicity to organisms, particularly aquatic organisms, cannot be neglected. In this study, the potential risks posed to zebrafish when exposed to environmental residual concentrations of BP-3 were evaluated. Zebrafish embryos (F0) were exposed to 0, 0.056, 2.3, and 38 µg/L BP-3 until 42 days' post-fertilization (dpf). The effects of BP-3 on the sex ratio and gene expression of F0 zebrafish were investigated. In the F1 embryos, cumulative hatching rate, body length, and heartbeats were observed. The result showed that F0 and F1 exposure to concentrations of 0.056 and 38 µg/L BP-3 elicited stronger toxicity at 96 hpf than single generation exposures. Overall, our results provide a new understanding on the effects of low BP-3 concentration chronic exposure on sex ratio and offspring developmental toxicity of the F0 zebrafish.

2D gel electrophoresis reveals dynamics of t-loop formation during the cell cycle and t-loop in maintenance regulated by heterochromatin state.

Linear chromosome ends are capped by telomeres that have been previously reported to adopt a t-loop structure. The lack of simple methods for detecting t-loops has hindered progress in understanding the dynamics of t-loop formation and its function in protecting chromosome ends. Here, we employed a classical two-dimensional agarose gel method (2D gel method) to innovatively apply to t-loop detection. Briefly, restriction fragments of genomic DNA were separated in a 2D gel, and the telomere sequence was detected by in-gel hybridization with telomeric probe. Using this method, we found that t-loops are present throughout the cell cycle, and t-loop formation tightly couples to telomere replication. We also observed that t-loop abundance positively correlates with chromatin condensation, i.e. cells with less compact telomeric chromatin (ALT cells and trichostatin A (TSA)-treated HeLa cells) exhibited fewer t-loops. Moreover, we observed that telomere dysfunction-induced foci, ALT-associated promyelocytic leukemia bodies, and telomere sister chromatid exchanges are activated upon TSA-induced loss of t-loops. These findings confirm the importance of the t-loop in protecting linear chromosomes from damage or illegitimate recombination.

Kinetics of inhibitory effect of isoferulic acid on mushroom tyrosinase.

A study on the kinetics of inhibitory effect of isoferulic acid on the monophenolase and diphenolase activity of mushroom tyrosinase was carried out using enzymological kinetic analysis method in a Na2HPO4-NaH2PO4 buffer solution (pH = 6.8) at 30°C. It was found that isoferulic acid efficiently inhibits both monophenolase and diphenolase activities of mushroom tyrosinase under experimental conditions. Concentrations of isoferulic acid leading to 50% rate inhibition (IC50) on monophenolase and diphenolase activity were calculated to be 0.13 mmol/L and 0.39 mmol/L, respectively, which are much lower than that of arbutin (IC50 = 5.3 mmol/L for diphenolase activity). The presence of isoferulic acid also prolongs the lag period in the oxidation process of l-tyrosine via tyrosinase-a 4.3-min lagging was observed with the presence of 0.20 mmol/L isoferulic acid-compared to a 1.1-min lagging in the absence of isoferulic acid. The Lineweaver-Burk plot demonstrates a competitive behavior of isoferulic acid in the tyrosinase oxidation of l-3,4-dihydroxyphenylalanine, with maximum reaction rate (vm) and inhibition constant (KI) at 64.5 µM/min and 0.11 mmol/L, respectively.

An ion-imprinted imidazole-functionalized ordered mesoporous silica for selective removal of chromium(VI) from electroplating effluents.

In this work, ion imprinted technology incorporated with mesoporous silica materials (MCM-41) to obtain the novel specific adsorbent, ion imprinted mesoporous silica. Cr(VI) imprinted mesoporous silica (Cr(VI)IMS) was synthesized and used for adsorption studies and waste water application. A synthesized imidazolyl silane agent act as the functional monomer in the imprinted process to build up highly ordered functionalized imprinted materials. The chemical composition, porosity, and highly ordered morphology were characterized by Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance (NMR), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. The Brunauer-Emmett-Teller (BET) surface area was 1054.51 m2 g-1 in this study. The Cr(VI)IMS showed great adsorption capacity to hexavalent chromium ions in acidic solution up to 45.6 mg g-1. Cr(VI)IMS reached the adsorption equilibrium in a short time (10 min) at acid and weak acid conditions, while most of adsorbents need more than 30 min to achieve adsorption equilibrium. Cr(VI)IMS displayed much higher adsorption capacity to Cr(VI) ions than other negative ions. The relative selectivity coefficient was 2.56, higher than those of other anions (below 1.5). After eight adsorption-regeneration cycles, the adsorption efficiency of Cr(VI)IMS still reached 92.5%. The Cr(VI)IMS was found to exhibit equivalent property after multiple cycles of experiments, indicating good repeatability and reproducibility.

A novel target and pH dual-activatable fluorescent probe for precisely detecting hypochlorite in lysosomes.

Hypochlorite (HClO) is involved in various physiological and pathological processes as well as regulation of lysosomal functions. Thus, it is appreciated to develop efficient molecule tools for precisely detecting HClO in lysosomes. Although several lysosomal-targetable fluorogenic probes for HClO have been developed to date, they still suffered from the discounted sensing performance under lysosomal acidic condition. Herein, on the basis of the "AND" logic gate strategy, a novel dual-activatable fluorogenic probe CS has been rationally designed by simultaneously incorporating HClO recognition site and pH-sensitive group with lysosomal-targetable characteristic into a coumarin fluorophore. Different from the single-activated ones previously reported, CS exhibited good sensitivity, high specificity and fast response towards HClO under the acidic conditions but was out of operation in the neutral or alkaline environment. Importantly, it had been successfully applied for spatial-resolution imaging of exogenous or endogenous HClO in lysosomes.

Inhibitory kinetics of paeonol on the activity of mushroom tyrosinase oxidizing L-dopa.

AIM: To evaluate the effect of paeonol on the activity of tyrosinase and provide experimental evidence for the treatment of hyperpigmentation disorders. METHODS: Tyrosinase activity was estimated by measuring the oxidation rate of L-3,4-dihydroxyphenylalanine (L-Dopa). The inhibitory effects of paeonol on the activity of mushroom tyrosinase and Michaelis-Menten kinetics were deduced from the Lineweaver-Burk plots. RESULTS: The inhibitory concentration of paeonol leading to 50% enzyme activity lost (IC50) was estimated to be 0.60 mmol x L(-1). The inhibition constants for paeonol binding free enzyme, K(I), and substrate-enzyme, K(IS), are 0.084 and 0.12 mmol x L(-1), respectively. CONCLUSION: Paeonol is a potential mixed inhibitor of mushroom tyrosinase. The mixed inhibition function may originate from its ability to form a Schiff base with a primary amino group and to chelate copper at the active site of tyrosinase.

[Microwave-assisted extraction technology of skin-lightning agent in Rhizoma Typhonii].

The microwave-assisted extraction (MAE) technology of skin-lightning agent in Rhizoma Typhonii was studied and the relative inhibitory activity of the extract against tyrosinase was used as evaluating criterion. It was concluded that the optimal condition was two doses of microwave radiation (450 W) for 7 min with a mass ratio of water to material of 10: 1. The dry extract of Rhizoma Typhonii with 20.9% yield and 47.1% relative inhibitory activity against tyrosinase was obtained. Compared with direct-heating extraction, MAE can shorten extracting duration, and improve relative inhibitory activity of the extract against tyrosinase.