Low-temperature catalysts of mesoporous Co 3 O 4 and Au/Co 3 O 4 with high catalytic activities for the trace ethylene oxidation at 0°C are reported in this paper. The catalysts were prepared by using the nanocasting method, and the mesostructure was replicated from three-dimensional (3D) cubic KIT-6 silicas. High resolution transmission electron microscopy (HRTEM) studies revealed that {110} facets were the exposed active surfaces in the mesoporous Co 3 O 4 , whereas the Co 3 O 4 nanosheets prepared by the precipitation method exhibited the most exposed {112} facets. We found that the mesoporous Co 3 O 4 was significantly more active for ethylene oxidation than the Co 3 O 4 nanosheets. The results indicated that the crystal facet {110} of Co 3 O 4 played an essential role in determining its catalytic oxidation performance. The synthesized Au/Co 3 O 4 materials, in which the gold nanoparticles were assembled into the pore walls of the Co 3 O 4 mesoporous support, exhibited stable, highly dispersed, and exposed gold sites. Gold nanoparticles present on Co 3 O 4 readily produced surface-active oxygen species and promoted ethylene oxidation to achieve a 76% conversion at 0°C, which is the highest conversion reported yet.

The recent explosive outbreak of Zika virus (ZIKV) infection has been reported in South and Central America and the Caribbean. Neonatal microcephaly associated with ZIKV infection has already caused a public health emergency of international concern. No specific vaccines or drugs are currently available to treat ZIKV infection. The ZIKV helicase, which plays a pivotal role in viral RNA replication, is an attractive target for therapy. We determined the crystal structures of ZIKV helicase-ATP-Mn2+ and ZIKV helicase-RNA. This is the first structure of any flavivirus helicase bound to ATP. Comparisons with related flavivirus helicases have shown that although the critical P-loop in the active site has variable conformations among different species, it adopts an identical mode to recognize ATP/Mn2+. The structure of ZIKV helicase-RNA has revealed that upon RNA binding, rotations of the motor domains can cause significant conformational changes. Strikingly, although ZIKV and dengue virus (DENV) apo-helicases share conserved residues for RNA binding, their different manners of motor domain rotations result in distinct individual modes for RNA recognition. It suggests that flavivirus helicases could have evolved a conserved engine to convert chemical energy from nucleoside triphosphate to mechanical energy for RNA unwinding, but different motor domain rotations result in variable RNA recognition modes to adapt to individual viral replication.Electronic supplementary materialThe online version of this article (doi:10.1007/s13238-016-0293-2) contains supplementary material, which is available to authorized users.

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To understand the nature and possible sources of environmentally persistent free radicals (EPFRs) in atmospheric aerosols, the present study used a solvent extraction method to fractionate aerosol components with different polarities and solvent resistance in fine particulate matter (PM) from Xi'an, China. The characteristics of EPFRs, that is., their concentration, type and lifetime, were obtained based on their electron paramagnetic resonance spectra. The results showed that the EPFRs in the PM samples were carbon-centered with a nearby heteroatom ( g = 2.0031) and had a long half-life of more than 3 years. Nearly all of the extractable EPFRs were detected in the water-insoluble organic fraction and showed characteristics indicating that may contain oxygen-centered radical ( g = 2.0038). Most of the total EPFRs in the PM were derived from solvent-resistant organic matter (88%), which likely consisted of graphene oxide analogues. The results suggest that previous studies may have missed the major proportion of EPFRs in atmospheric particulates if they only focused on solvent-extractable or metallic oxide-formed EPFRs. Our results showed that the EPFR concentration was significantly and positively correlated with the elemental carbon and NO concentrations, suggesting that traffic emissions may be an important source of EPFRs in PM over Xi'an.

a b s t r a c tIn this study, bimetallic Ni/Fe nanoparticles were prepared and the ability of this material to degrade DDT in aqueous solution was investigated at room temperature. Besides comparing the degradation rates of DDT using monometallic zero-valent iron and bimetallic Ni/Fe, batch investigations with bimetallic Ni/Fe nanoparticles were conducted to explore the influence of pH value on the degradation rate of DDT in aqueous solution. Results indicate that weakly acidic (4 ≤ pH < 7) or alkaline reaction (7 < pH ≤ 10) conditions afford faster degradation rates, whereas higher or lower pH inhibits the DDT degradation. In addition, the DDT degradation exhibits an interesting pathway and mechanism at higher pH value (pH > 10) in reaction solution. In strong alkaline solution, the DDT degradation becomes slow but is not quenched. The electron transfer for DDT degradation is enhanced by creating numerous galvanic cells under the Ni catalysis, and promotes the dehydrochlorination reaction. The hydrodechlorination reaction in alkaline condition is also unbroken. This phenomenon is quite different from those reported in other studies previously.

During its life cycle, Zika virus (ZIKV), an arthropod-borne flavivirus that is associated with Guillain-Barré syndrome and causes microencephaly in fetuses and newborn children, encodes a critical and indispensable helicase domain that has 5'-triphosphatase activity and performs ATP hydrolysis to generate energy and thus, sustains unwinding of double-stranded RNA during ZIKV genome replication. Of these processes, ATP hydrolysis represents the most basic event; however, its dynamic mechanisms remain largely unknown, impeding the further understanding of the function of ZIKV helicase and the ongoing anti-ZIKV drug design. In this work, we determined the crystal structure of ZIKV helicase in complex with ADP-AlF-Mn and ADP-Mn separately. The structural analysis indicates that these structures represent the intermediate state and posthydrolysis state, respectively, of the ATP hydrolysis process of ZIKV helicase. These findings, together with our earlier work, which identified the prehydrolysis state of ZIKV helicase, lead to a proposal of the ATP hydrolysis cycle for ZIKV helicase. On this basis, we used site-directed mutagenesis combined with an enzymatic study to identify successfully residues that are critical for the ATPase activity of ZIKV helicase; this will provide new ideas to understand the function for the key enzyme of ZIKV.-Yang, X., Chen, C., Tian, H., Chi, H., Mu, Z., Zhang, T., Yang, K., Zhao, Q., Liu, X., Wang, Z., Ji, X., Yang, H. Mechanism of ATP hydrolysis by the Zika virus helicase.

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