A DFT and kinetic study: Is it possible to prepare epoxides without catalysts using the in-situ generated peroxy radicals or peroxides by one-step method?

DFT calculations and kinetic analysis have been employed to comprehensively explore the possibility to prepare epoxides by one-step method using the in-situ generated peroxy radicals or hydroperoxides as epoxidizing agents. Computational studies demonstrated that the selectivities for the reaction systems of O2 /R2/R1, O2 /CuH/R1, O2 /CuH/styrene, O2 /AcH/R1 were 68.2%, 69.6%, 100% and 93.3%, respectively. The in-situ generated peroxide radicals, such as HOO˙, CuOO˙ and AcOO˙, could react with R1 or styrene by attacking the CC double bond to form a CO bond and subsequently undergoing a cleavage of OO bond to yield epoxides. Peroxide radicals could abstract a hydrogen atom from methyl group on R1, forming unwanted by-products. It should be noted that the hydrogen atoms of HOO˙ is easy to be abstracted by CC double bond and simultaneously the oxygen atom is connected to the CH moiety to form an alkyl peroxy radical (Rad11), greatly limiting the selectivity. The comprehensive mechanistic studies provide a deep understanding on preparing epoxides by one-step method.

Biomimetic Antithrombotic Tissue-Engineered Vascular Grafts for Converting Cholesterol and Free Radicals into Nitric Oxide.

Small-diameter tissue-engineered vascular grafts (sdTEVGs) are essential materials used in bypass or replacement surgery for cardiovascular diseases; however, their application efficacy is limited because of patency rates, especially under hyperlipidemia, which is also clinically observed in patients with cardiovascular diseases. In such cases, improving sdTEVG patency is challenging because cholesterol crystals easily cause thrombosis and impede endothelialization. Herein, the development of a biomimetic antithrombotic sdTEVG incorporating cholesterol oxidase and arginine into biomineralized collagen-gold hydrogels on a sdTEVG surface is described. Biomimetic antithrombotic sdTEVGs represent a multifunctional substrate for the green utilization of hazardous substances and can convert cholesterol into hydrogen peroxide, which can react with arginine to generate nitric oxide (NO). NO is a vasodilator that can simulate the antithrombotic action of endothelial cells under hyperlipidemic conditions. In vivo studies show that sdTEVGs can rapidly produce large amounts of NO via a cholesterol catalytic cascade to inhibit platelet aggregation, thereby improving the blood flow velocity and patency rates 60 days after sdTEVG transplantation. A practical and reliable strategy for transforming "harmful" substances into "beneficial" factors at early transplantation stages is presented, which can also promote vascular transplantation in patients with hyperlipidemia.

PtoMPO1, a negative mediator, functions in poplar drought tolerance.

Drought, as one of the most severe abiotic stresses in nature, adversely affects plant growth and development. Poplar is a woody plant which is prone to water-deficit sensitivity. Therefore, it is important to improve our understanding of how poplar responds to drought stress. Here, we cloned a gene from Populus tomentosa, namely PtoMPO1. PtoMPO1 encodes a DUF962 domain protein that is a homolog of yeast dioxygenase Mpo1 and Arabidopsis MHP1. The transcripts of PtoMPO1 were repressed by drought stress and ABA. Atmhp1-1 was a T-DNA insertion mutant lacking AtMHP1, and heteroexpression of PtoMPO1 in Atmhp1-1 significantly alleviated the sensitivity of Atmhp1-1 to ABA and NaCl, implying the functional replacement of PtoMPO1 to AtMHP1. PtoMPO1 overexpression decreased but PtoMPO1 mutation enhanced poplar drought tolerance. Furthermore, the expression of drought-related gene PtoRD26 is markedly lower in PtoMPO1-overexpressing plants and notably higher in Ptompo1 mutants compared to that in the wild type. Overall, these results suggested that PtoMPO1 functions as a novel negative mediator for drought tolerance in poplar.

Electronic Properties and Carrier Dynamics at the Alloy Interfaces of WS2x Se2-2x Spiral Nanosheets.

Electronic properties at the interfaces between different-composition domains of 2D-alloys are key for their optical, electronic, and optoelectronic applications. Understanding the interfacial electronic structures and carrier dynamics is essential for designing and fabricating devices that use these alloys. Here, WS2x Se2-2x spiral nanosheets are prepared using the physical vapor deposition method, and the nonlinear optical and electronic properties, as well as the carrier dynamics at the interfaces between the WS and WSe domains, are studied. Second-harmonic generation tests demonstrate that these nanosheets exhibit a very strong layer-dependent nonlinear optical effect. Atomic-resolution scanning tunneling microscopy (STM) and spectroscopy (STS) measurements reveal that S and Se atoms are non-uniformly distributed, forming WS domains, WSe domains, and defect-related areas. Atomic STM images and STS maps reveal enhanced local density of states by electron scattering at the WS/WSe interfaces, providing a detailed nanoscale interpretation of the S/Se-ratio-dependent lifetimes observed in pump-probe spectroscopy measurements. This work provides valuable interfacial characterization of 2D-alloy materials, using state-of-the-art methods with high temporal and spatial resolutions. The obtained insights are likely to be useful for prospective applications.