Cytosine base editors (CBEs) enable efficient cytidine-to-thymidine (C-to-T) substitutions at targeted loci without double-stranded breaks. However, current CBEs edit all Cs within their activity windows, generating undesired bystander mutations. In the most challenging circumstance, when a bystander C is adjacent to the targeted C, existing base editors fail to discriminate them and edit both Cs. To improve the precision of CBE, we identified and engineered the human APOBEC3G (A3G) deaminase; when fused to the Cas9 nickase, the resulting A3G-BEs exhibit selective editing of the second C in the 5′-CC-3′ motif in human cells. Our A3G-BEs could install a single disease-associated C-to-T substitution with high precision. The percentage of perfectly modified alleles is more than 6000-fold for disease correction and more than 600-fold for disease modeling compared with BE4max. On the basis of the two-cell embryo injection method and RNA sequencing analysis, our A3G-BEs showed minimum genome- and transcriptome-wide off-target effects, achieving high targeting fidelity.
Selective catalytic reduction (SCR) of NO x with H 2 as ar eductant is the most promising denitration technology at low temperature. Achieving the conversion of NO x into N 2 at ambient temperature not only prolongs the service life of the catalyst, but also provides more freedomf or the arrangemento fd enitration units throughout the flue gas treatment equipment.H owever,t he development of highly efficient,s table, and environmentally benign supported platinum-based catalysts for H 2 -SCR at ambientt emperature is still am ajor challenge. Herein, a0 .5 wt %P t/ZrO 2 @C catalyst, which was composed of carbon-coated octahedral ZrO 2 with highly dispersed Pt particles, was prepared by using an ew stabilization strategy based on UiO-66-NH 2 (a zirconium metal-organic framework) as at emplate. The catalytic performance of this Pt/ZrO 2 @C in H 2 -SCR was tested and confirmed to achieven ear 100 %N O x conversion at 90 8C. Also, 70 %N 2 selectivity of the catalyst was achieved. The morphology, structure, and porous properties of the as-synthesized nanocomposites were characterizedb yu sing data obtained from field-emission SEM, TEM, XRD, Ramans pectroscopy,t hermogravimetric analysis,X -ray photoelectrons pectroscopy,a nd N 2 adsorption-desorption isotherms. The results show that residual carbon formed by pyrolysis treatment is coated on octahedral ZrO 2 ,a nd effectively prevents the agglomeration of platinum particles on the surface.
Zirconium diboride is one of the most promising ultra high temperature ceramics, which are urgently required in the development of hypersonic flight, atmospheric re-entry and rocket propulsion. In this work, the zirconium diboride coating is successfully obtained on different substrates by electrochemical deposition from a NaCl-KCl-K 2 ZrF 6 -KBF 4 melt. The effects of current density, operating temperature, electrodeposition time and substrate materials on the microstructure and phase composition of the coating are also investigated by SEM, EDX, and XRD. Besides, the electrochemical reduction of zirconium, boron and zirconium diboride has been investigated by cyclic voltammetry and chronopotentiometry. The results show that various morphological and structure of ZrB 2 coatings can be synthesized on stainless steel, graphite and carbon fiber reinforced carbon composite (C/C composite) substrates and the synthesis of ZrB 2 mainly follow two subsequent electrochemical reactions and a chemical reaction.
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