Search

Let C be an abelian monoidal category. It is proved that the nilpotent category Nil (C) of C admits almost monoidal structure except the unit axiom. As an application, it is proved that Hom and Tensor functors exist over Nil (C) and tensor–hom adjunction remains true over the nilpotent category of the category of finite-dimensional vector spaces, which develops some recent results on this topic. [ABSTRACT FROM AUTHOR]

Oxygen evolution reaction catalysts capable of working efficiently in acidic media are highly demanded for the commercialization of proton exchange membrane water electrolysis. Herein, we report a Zn-doped RuO2 nanowire array electrocatalyst with outstanding catalytic performance for the oxygen evolution reaction under acidic conditions. Overpotentials as low as 173, 304, and 373 mV are achieved at 10, 500, and 1000 mA cm−2, respectively, with robust stability reaching to 1000 h at 10 mA cm−2. Experimental and theoretical investigations establish a clear synergistic effect of Zn dopants and oxygen vacancies on regulating the binding configurations of oxygenated adsorbates on the active centers, which then enables an alternative Ru−Zn dual-site oxide path of the reaction. Due to the change of reaction pathways, the energy barrier of rate-determining step is reduced, and the over-oxidation of Ru active sites is alleviated. As a result, the catalytic activity and stability are significantly enhanced. Ru-based materials are promising catalysts for oxygen evolution reaction in acidic condition, but their catalytic performance needs to be further improved. Here, the authors report Zn-RuO2 nanowires with a Ru−Zn dual-site oxide reaction pathway with enhanced activity and stability for acidic oxygen evolution reaction. [ABSTRACT FROM AUTHOR]

In present study, we have mined a transaminase (TA) from Rhizobium sp. from the pool of fully sequenced genomes by using an ω-TA sequence from Vibrio fluvialis JS17 as a template in a BLASTP search. The protein sequence of the TA from Rhizobium sp. exhibits 53% sequence identity to that from V. fluvialis. The TA with S-selectivity showed close evolutionary relationship with a pyruvate transaminase from Alcaligenes denitrificans Y2k-2 and an S-selective aminotransferase from Sphaerobacter thermophilus. The gene of the ω-TA was inserted into pET-28a and functionally expressed in E. coli BL21. Results showed that the recombinant ω-TA has a specific activity of 7.46 U/mg at pH 8.0, 30 ℃. The substrate specificity test found the ω-TA presented significant reactivity toward aromatic amino donors and amino acceptors containing aldehydes. More importantly, the ω-TA also exhibited a good affinity towards some cyclic substrates. The homology model of the ω-TA was built by Discovery Studio and docking was performed to describe the relative activity towards some substrates. [ABSTRACT FROM AUTHOR]

Background: Laccase, a multicopper oxidase that catalyzes the oxidation of phenols, aromatic amines, and benzenethiols, has attracted much attention in applications of organic synthesis, bioremediation, and pulp/textile bleaching. However, free laccases cannot be recycled and are easily inactivated in diverse environmental conditions. Enzyme immobilization is a promising strategy to improve stability, resistance to extreme conditions, and reusability of laccase.Results: In this study, amino-functionalized magnetic Fe3O4 nanoparticles were synthesized for co-immobilization of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and laccase by glutaraldehyde cross-linking method. The magnetic nanoparticles were characterized with FTIR, XRD and VSM. Cyclic voltammetry was carried out to verify electrochemical behaviors of the co-immobilized laccase and TEMPO nanoparticles. When the co-immobilized laccase and TEMPO nanoparticles were used to decolorize acid fuchsin, the maximum decolorization rate of 77.41% was obtained with the ratio of TEMPO to laccase being 0.3 mM/g:120 U/g.Conclusion: The co-immobilized nanoparticles retained above 50% residual activity after eight cycles of operation, which presented an approach to develop a co-immobilized laccase and mediator system for potential industrial application. [ABSTRACT FROM AUTHOR]