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Oxalicine B (1) is an α -pyrone meroterpenoid with a unique bispirocyclic ring system derived from Penicillium oxalicum. The biosynthetic pathway of 15-deoxyoxalicine B (4) was preliminarily reported in Penicillium canescens , however, the genetic base and biochemical characterization of tailoring reactions for oxalicine B (1) has remained enigmatic. In this study, we characterized three oxygenases from the metabolic pathway of oxalicine B (1), including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/ α -KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 OxaB. Intriguingly, OxaK can catalyze various multicyclic intermediates or shunt products of oxalicines with impressive substrate promiscuity. OxaB was further proven via biochemical assays to have the ability to convert 15-hydroxdecaturin A (3) to 1 with a spiro-lactone core skeleton through oxidative rearrangement. We also solved the mystery of OxaL that controls C-15 hydroxylation. Chemical investigation of the wild-type strain and deletants enabled us to identify 10 metabolites including three new compounds, and the isolated compounds displayed potent anti-influenza A virus bioactivities exhibiting IC 50 values in the range of 4.0−19.9 μmol/L. Our studies have allowed us to propose a late-stage biosynthetic pathway for oxalicine B (1) and create downstream derivatizations of oxalicines by employing enzymatic strategies. The late-stage biosynthetic pathway of meroterpenoid oxalicine B was proposed, and three oxygenases, including a cytochrome P450 hydroxylase OxaL, a hydroxylating Fe(II)/ α -KG-dependent dioxygenase OxaK, and a multifunctional cytochrome P450 monooxygenase OxaB, were biochemically characterized. [Display omitted] [ABSTRACT FROM AUTHOR]

Metal anodizations have attracted much attention, but the formation mechanisms of the porous anodic oxides are still unclear. Compared with the Ti anodization, the anodization of Zr is relatively less studied. In order to compare the anodizing processes of Ti and Zr, a comparative study of Ti and Zr was carried out under the different voltages of anodizing process in the same mixed electrolyte of ammonium fluoride and phosphate acid. It was found that the structure and morphology of their nanotubes were very different. The anodizing curve of Ti showed a state of constant current. However, the anodizing curve of Zr did not show the state of constant current and ZrO 2 nanotubes were still formed. This indicates that there is no equilibrium between oxide growth and dissolution in the anodization. TiO 2 nanotubes show an orderly array of nanotubes, but ZrO 2 nanotubes have three kinds of composite structures: nanoflower, nanotube and dense films. By comparing the great difference of current-time curves between the two anodizing processes, the composite structure of ZrO 2 nanotubes are interpreted reasonably by combining electronic current theory and oxygen bubble mold. [ABSTRACT FROM AUTHOR]

This study investigated the removal of tetracycline (TC) using multilayered graphene-phase biochar (MGB) derived from waste chicken feather. MGB was produced through a two-stage carbonization and KOH-activation method. MGB was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), Fourier transform infrared (FT-IR), Raman spectra, Zeta potential and elemental analysis. Various chemical functional groups were demonstrated on the surface of MGB. MGB was featured by a very large BET surface area of 1838 m 2 /g. A rapid equilibrium (within 30 s) and an ultrahigh removal efficiency (up to 99.65%) were obtained when MGB was used in the adsorption of TCs. The adsorption processes were temperature-dependent and the maximum adsorption capacity of MGB was 388.33 mg/g at 30 °C. The data of adsorption isotherms and kinetics were represented well by the Langmuir and Elovich models, respectively. The chemical monolayer adsorption could play an important role in this process. Furthermore, the adsorption of MGB was tolerant with wide pH, high ionic strength and even co-existing anions. Regeneration experiments indicated the removal efficiency was still satisfied (96.61%) even after four cycles. These results have important implications for the future application of animal waste-derived adsorbents in the treatment of wastewater containing antibiotic residues. [ABSTRACT FROM AUTHOR]