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Baicalin, a flavonoid compound extracted from the dry root of Scutellaria baicalensis Georgi, has been shown to have anti-inflammation, anti-viral, anti-bacterial, and immunomodulatory activity. However, the effect of baicalin against avian infectious bronchitis virus (IBV) remains unknown. The purpose of this study was to investigate the anti-IBV activity and underlying mechanism of baicalin in vitro. The results showed that baicalin has a direct virucidal effect but no prophylactic effect on IBV infection. The mRNA and protein of IBV N were decreased significantly when IBV-infected cells were treated with baicalin during the multiple stages of the virus replication cycle, including viral adsorption, invasion, internalization, and release. Stress granule (SG) formation resulted from the increase of G3BP1 and the phosphorylation of the PKR/eIF2α due to the treatment of IBV-infected cells with baicalin. The inhibitory activity of baicalin on IBV replication was increased when G3BP1 expression was inhibited, and the down-regulation of G3BP1 expression occurred when the expression of PKR and eIF2α was inhibited. These findings revealed that baicalin activates phosphorylation of the PKR/eIF2α pathway and induces SG formation by targeting G3BP1, initiating the antiviral response to suppress IBV replication in Vero cells. The results suggest that baicalin is a promising candidate drug to treat or prevent IBV infection. RESEARCH HIGHLIGHTS Baicalin inhibits IBV replication by reducing IBV N protein and mRNA. Baicalin disturbs multiple stages of the IBV life cycle. Baicalin activates PKR/eIF2α pathway and induces stress granule formation to exert anti-IBV response. [ABSTRACT FROM AUTHOR]

Graphene quantum dots (GQDs), inheriting the superb property of graphene oxide, possess smaller lateral size and high biocompatibility, thus having potential in biomedical applications. We previously discovered that GQDs, combining with Cu2+ions, could cleave DNA primarily through an oxidative pathway; yet, oxidative DNA cleavage is not practically preferred in biology. In this work, we explore the DNA cleavage ability of GQDs with Zn2+and Ni2+. Zn2+and Ni2+alone are incapable of cleaving supercoiled DNA, but when combining with the GQDs, Zn2+and Ni2+exhibit DNA cleavage activity. However, the activity of these two systems is much lower than that of GQDs/Cu2+, and GQDs/Ni2+is less active than GQDs/Zn2+. The functional mechanism of GQDs/Ni2+and GQDs/Zn2+is different from that of GQDs/Cu2+. The GQDs play a key role in the two systems; the redox inactive Zn2+and Ni2+ions assist to generate the oxidative species that eventually lead to the DNA cleavage. The current results together with our previous result indicate that GQDs together with metal ions can cleave supercoiled DNA, and their cleavage activities depend on the properties of metal ions: for redox active metal ions, metal ions play key roles, for redox inactive metal ions, GQDs are dominant. [ABSTRACT FROM PUBLISHER]

A reliable indirect competitive enzyme-linked immunosorbent assay (ELISA) based on a new specific monoclonal antibody was developed to determine olaquindox in animal feed. The influence of several physicochemical factors (nonfat dried milk solution, organic solvent, incubation time) on the immunoassay was investigated. In the optimized system, the 50% inhibition concentration was 9.66 ± 1.81 µ g L−1. The limits of detection for porcine, chicken, and fish feed were 0.28, 0.46, and 0.48 µg kg−1. The limits of quantification were 1.00 µg kg−1for the feed samples. The recoveries from porcine, chicken, and fish feed spiked with olaquindox were 90–104%, 77–103%, and 78–107%, respectively, with coefficients of variation (CVs) between 3.8 and 14.1%. The cross-reactivity was less than 2.08% with four structurally related compounds and no recognition of five other restricted or forbidden drugs was observed. Parallel analysis of the three spiked feed samples showed comparable results between the indirect competitive ELISA and the standard high-performance liquid chromatography method in China (R2 = 0.9985 for porcine feed, R2 = 0.9896 for chicken feed, and R2 = 0.9987 for fish feed). These data suggest that the developed indirect competitive ELISA is a specific and convenient method and is suitable for olaquindox determination in animal feed. [ABSTRACT FROM PUBLISHER]

To explore the effect of the metal center on catechol oxidase and tyrosinase activities, four complexes, Cu2(μ-Cl)2(hbpg)2 (1), [Cu2(μ-OH2)2(hbpg)2](NO3)2(H2O)2 (2), [Fe2(μ-Cl)2(hbpg)2]Cl2(H2O)2 (3), and [Mn2(μ-Cl)2(hbpg)2](H2O)2 (4) (hbpg = N-(2-hydroxybenzyl)-N-(2-picolyl)glycine), were synthesized and characterized with elemental analysis, single-crystal X-ray diffraction, molar conductivity measurements, mass spectrometry, UV-Visible, and FT-IR spectroscopies. The X-ray crystal structural analysis indicates that 1 has a binuclear copper, coordinated with N2O2 ligands. Complementary characterizations suggested that 2, 3, and 4 have similar coordination sphere. Complex 3 exhibits much higher catechol oxidase and tyrosinase-like activity than 1, 2, and 4. The results suggested that with a similar coordination sphere, the redox potential of the metal center is critical for catalytic activity. This work provides valuable information for improving the polyphenol oxidase activity of metal complexes for phenolic degradation. [ABSTRACT FROM PUBLISHER]

Catalase-like activity of a dinuclear manganese-salen (Mn-salen) complex, [Mn(salen)(H2O)]2(ClO4)2 (salen = N,N '-bis(salicylidene)-1,2-diaminoethane), was investigated. The dinuclear Mn-salen complex exhibits higher catalase-like activity than that of the mononuclear Mn-salen compound, and its activity can be enhanced by an external base. Different reaction intermediates in the presence and absence of an external base were observed, and the catalytically active species was dimeric as evidenced by UV-Vis spectroscopic studies and mass spectrometry data. [ABSTRACT FROM AUTHOR]