氢转移反应对分子筛催化甲醇和二甲醚动态自催化反应历程的贡献:深入理解甲醛的生成机理和作用机制

甲醇制烯烃(MTO)已成为从非石油资源获取低碳烯烃的最为成功的工业化路线,受到学术界和工业界的广泛关注.MTO反应是一个动态的自催化过程,其中烯烃、甲基环戊烯和芳烃物种作为(自)催化剂.氢转移(HT)反应是构建MTO自催化剂和烷烃副产物的主要途径,对于深入理解MTO反应的动态特性及其复杂反应网络至关重要.作为反应物甲醇/二甲醚发生HT反应的产物,甲醛对MTO反应中自催化的引发和失活具有重要作用.然而,由于甲醛的反应活性高、浓度低且对色谱FID检测器的灵敏度低,因此甲醛难以像其它烃类产物一样通过常规手段进行在线定量监测,迄今甲醛在整个反应过程中的演变规律仍不清楚,这阻碍了对反应物诱导的HT反应以及整个反应网络的全面认识.本文借助实验及理论计算研究了SAPO-34分子筛上甲醇和二甲醚转化过程中的HT反应,尤其是生成甲醛的反应物诱导的HT反应.首先,建立了一种定量检测甲醛的实验方法,实现在真实反应条件下,原位定量监测整个MTO和二甲醚制烯烃(DTO)过程中甲醛浓度的变化.在此基础上,将甲醛浓度变化规律与其它反应规律关联起来,更为详细地追踪整个反应过程中H原子的轨迹,并进一步结合DFT计算、operando光谱分析、12C/13C同位素切换、失活动力学分析,研究了MTO/DTO不同反应阶段中甲醛的生成机理,揭示了甲醇和二甲醚的甲基化活性和氢转移活性,及其对反应网络和积碳失活的影响,从而确定了MTO和DTO反应的失活机理和模型.结合甲醛的定量检测,还研究了共进料H_(2)O和高压H_(2)对MTO/DTO反应的影响.综合上述信息,提出减缓催化剂积碳失活的策略,并加以实践应用.反应物诱导的HT反应在反应物未能完全转化的初始阶段和失活阶段尤为突出,两个阶段检测到少量和大量的甲醛,分别主要由分子筛催化的甲醇/二甲醚与甲氧基和烯烃之间的HT反应产生;而产物诱导的HT反应在高效反应阶段占主导地位.这种动态演变的HT反应作为“暗线”与作为“明线”的烯烃生成的主反应同时发生并相互作用,共同构成MTO和DTO完整的动态反应网络.HT反应不仅能够生成作为自催化剂的不饱和活性中间体,而且能够生成积碳并导致失活,对MTO自催化网络从启动到衰退的动态演变起到关键作用.DTO反应中,由于二甲醚的HT反应能力较弱,参与HT反应的能垒较高,因此,反应物诱导的HT反应受到抑制,相应的甲醛、烷烃以及缺氢物种的生成相对受到抑制,这使得DTO反应中烯烃循环相对突出,并表现出相对温和的反应历程和缓慢的失活过程.相比之下,甲醇具有很强的HT能力:一方面作为氢受体生成甲烷和缺氢物种,直接参与并促进积碳失活的发生;另一发面,作为氢供体生成甲醛,引发甲醛介导的失活过程,间接参与并促进积碳生成.同时,甲醇较强的HT能力加剧了甲醇甲基化反应与HT反应之间的竞争,使得反应物诱导的HT和失活过程在MTO反应中至关重要.共进料H_(2)O和高压H_(2)的MTO/DTO反应中仍然能够检测到甲醛,且含量略小于或者等于非共进料体系.特别指出,HT能力较弱和传质受限引起局部催化微环境中反应物的化学势较低是二甲醚反应的两大特点.共进料高压H_(2)对MTO反应的影响包括不饱和烃类物种的加氢、加氢消碳和抑制HT反应的发生.利用上述两点对反应机理的理解,采用二甲醚(而不是甲醇)与高压H_(2)共进料,可进一步使得反应过程中的HT反应受到抑制,进而调节动态反应网络以更温和的自催化演变方式发生,实现反应高效且长周期的运行,该反应过程具有实际工业应用潜力.综上,本工作的研究和实践尝试对于高效的工艺和催化剂的开发和应用,并以此实现对动态复杂反应网络的精准调控具有重要意义.

Coking and decoking chemistry for resource utilization of polycyclic aromatic hydrocarbons(PAHs)and low-carbon process

Low-carbon process for resource utilization of polycyclic aromatic hydrocarbons(PAHs)in zeolitecatalyzed processes,geared to carbon neutrality-a prominent trend throughout human activities,has been bottlenecked by the lack of a complete mechanistic understanding of coking and decoking chemistry,involving the speciation and molecular evolution of PAHs,the plethora of which causes catalyst deactivation and forces regeneration,rendering significant CO_(2) emission.Herein,by exploiting the high-resolution matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry(MALDI FT-ICR MS),we unveil the missing fingerprints of the mechanistic pathways for both formation and decomposition of cross-linked cage-passing PAHs for SAPO-34-catalyzed,industrially relevant methanol-to-olefins(MTO)as a model reaction.Notable is the molecule-resolved symmetrical signature:their speciation originates exclusively from the direct coupling of in-cage hydrocarbon pool(HCP)species,whereas water-promoted decomposition of cage-passing PAHs initiates with selective cracking of inter-cage local structures at 8-rings followed by deep aromatic steam reforming.Molecular deciphering the reversibly dynamic evolution trajectory(fate)of full-spectrum aromatic hydrocarbons and fulfilling the real-time quantitative carbon resource footprints advance the fundamental knowledge of deactivation and regeneration phenomena(decay and recovery motifs of autocatalysis)and disclose the underlying mechanisms of especially the chemistry of coking and decoking in zeolite catalysis.The positive yet divergent roles of water in these two processes are disentangled.These unprecedented insights ultimately lead us to a steam regeneration strategy with valuable CO and H_(2) as main products,negligible CO_(2) emission in steam reforming and full catalyst activity recovery,which further proves feasible in other important chemical processes,promising to be a sustainable and potent approach that contributes to carbon-neutral chemical industry.

Project-Based Teaching in Control Theory Education Based on V-REP: A Cart Inverted Pendulum Case

This paper provides a teaching concept for control theory education based on Virtual Robot Experimentation Platform(V-REP).A cart inverted pendulum virtual physical model is developed on V-REP.Students must analyze,design,and implement a suitable controller for the cart inverted pendulum system using their knowledge of the control theory.Different from traditional experiment and numerical simulation,virtual experiment is safe and less constrained.Moreover,the experiment results are more intuitive and obvious.This study can improve students’interest in learning the control theory and help students understand the relevant content better.

Three‑Dimensional Ordered Mesoporous Carbon Spheres Modified with Ultrafine Zinc Oxide Nanoparticles for Enhanced Microwave Absorption Properties

Currently,electromagnetic radiation and interference have a significant effect on the operation of electronic devices and human health systems.Thus,developing excellent microwave absorbers have a huge significance in the material research field.Herein,a kind of ultrafine zinc oxide(ZnO)nanoparticles(NPs)supported on three-dimensional(3D)ordered mesoporous carbon spheres(ZnO/OMCS)is prepared from silica inverse opal by using phenolic resol precursor as carbon source.The prepared lightweight ZnO/OMCS nanocomposites exhibit 3D ordered carbon sphere array and highly dispersed ultrafine ZnO NPs on the mesoporous cell walls of carbon spheres.ZnO/OMCS-30 shows microwave absorbing ability with a strong absorption(−39.3 dB at 10.4 GHz with a small thickness of 2 mm)and a broad effective absorption bandwidth(9.1 GHz).The outstanding microwave absorbing ability benefits to the well-dispersed ultrafine ZnO NPs and the 3D ordered mesoporous carbon spheres structure.This work opened up a unique way for developing lightweight and high-efficient carbon-based microwave absorbing materials.

Developing high-efficiency base editors by combining optimized synergistic core components with new types of nuclear localization signal peptide

The clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPR-associated protein(Cas) system has been widely used for genome editing. In this system, the cytosine base editor(CBE) and adenine base editor(ABE) allow generating precise and irreversible base mutations in a programmable manner and have been used in many different types of cells and organisms. However, their applications are limited by low editing efficiency at certain genomic target sites or at specific target cytosine(C) or adenine(A) residues. Using a strategy of combining optimized synergistic core components, we developed a new multiplex super-assembled ABE(sABE) in rice that showed higher base-editing efficiency than previously developed ABEs. We also designed a new type of nuclear localization signal(NLS) comprising a FLAG epitope tag with four copies of a codon-optimized NLS(F4NLS^(r2)) to generate another ABE named F4NLS-sABE. This new NLS increased editing efficiency or edited additional A at several target sites. A new multiplex super-assembled CBE(sCBE) and F4NLS^(r2) involved F4NLS-sCBE were also created using the same strategy. F4NLS-sCBE was proven to be much more efficient than sCBE in rice. These optimized base editors will serve as powerful genome-editing tools for basic research or molecular breeding in rice and will provide a reference for the development of superior editing tools for other plants or animals.

Highly efficient CRISPR-SaKKH tools for plant multiplex cytosine base editing

Base editing, as an expanded clustered regularly interspaced short palindromic repeats(CRISPR)-Cas genome editing strategy, permits precise and irreversible nucleotide conversion. SaKKH, an efficient variant of a Cas9 ortholog from Staphylococcus aureus(SaCas9), is important in genome editing because it can edit sites with HHHAAT protospacer adjacent motif(PAM) that the canonical Streptococcus pyogenes Cas9(SpCas9) or its variants(e.g. xCas9, Cas9-NG) cannot. However, several technical parameters of SaKKH involved base editors have not been well defined and this uncertainty limits their application. We developed an effective multiplex cytosine base editor(SaKKHn-pBE) and showed that it recognized NNARRT, NNCRRT, NNGRGT, and NNTRGT PAMs. Based on 27 targets tested, we defined technical parameters of SaKKHn-pBE including the editing window, the preferred sequence context, and the mutation type. The editing efficiency was further improved by modification of the SaKKH sgRNA. These advances can be applied in future research and molecular breeding in rice and other plants.

Effect of propofol pretreatment on apoptosis in rat brain cortex after focal cerebral ischemia and reperfusion

The present study aimed to observe cortical expression of Bcl-2 and Bax,cysteine-dependent aspartate directed proteases-3 activity and apoptotic cell death in a rat model of middle cerebral artery occlusion pretreated with propofol.Results showed that,propofol pretreatment significantly reduced oxidative stress levels and attenuated neuronal apoptosis in the cortex of rats.Propofol pretreatment upregulated Bcl-2 expression,and downregulated Bax expression and cysteine-dependent aspartate directed proteases-3 activity.These findings indicate that propofol pretreatment inhibits cell apoptosis during focal cerebral ischemia/reperfusion injury.This neuroprotective effect is most likely achieved through the Bcl-2/Bax/cysteine-dependent aspartate directed proteases-3 pathway.

Rapid Molecular Identification of Tribolium destructor

In this study, a rapid molecular identification method of Tribolium destructor was established with PCR and PCR-RFLP （polymerase chain reaction-restriction fragment length polymorphism） technology. According to the results, （ 1 ） with PCR method, specific primers were designed based on CO1 gene of T. destructor for PCR amplification, and electrophoresis detection confirmed that PCR method could be used to rapidly and accurately identify T. destructor; （2） with PCR-RFLP method, two pairs of degenerate primers were used to amplify CO1 gene of Tribolium species, PCR products were digested with HindIII and detected by electrophoresis, results indicated that PCR-RFLP method could also be used for rapid identification of T. destructor in quarantine practice.

以累积和分析法研究保留耻骨后间隙机器人辅助根治性前列腺切除术的学习曲线

目的通过应用累积和分析(CUSUM)法,探讨保留耻骨后间隙机器人辅助根治性前列腺切除术(RsRARP)的学习曲线,评估手术者的学习过程。方法回顾性分析2016年10月至2021年9月1日由单术者连续进行的161例RsRARP患者的临床资料。应用CUSUM法以手术时间作为衡量指标分析RsRARP学习曲线。根据CUSUM分析结果,确定手术学习曲线的拐点,利用学习曲线变化的拐点划分学习阶段,比较学习曲线各阶段的术中失血量、手术时间、并发症、切缘阳性率和术后尿控等指标。并采用Kaplan-Meier曲线计算术后尿控情况。结果161例患者手术均顺利完成,无中转开放。根据CUSUM分析,学习曲线可分为三个阶段:早期学习37例,技能提高71例,熟练掌握53例。随着手术例数的增加,手术时间明显缩短(P<0.001),术中出血明显减少(P<0.001),术后住院时间明显缩短(P<0.001)。熟练掌握阶段中位手术时间为185 min,术后即刻尿控率为64.2%,pT_(2)期患者切缘阳性率为11.3%,pT_(2)期患者的1年无生化复发率为96.7%。三个阶段的即刻尿控率、并发症发生率、切缘阳性率、生化复发率差异无统计学意义。结论通过应用CUSUM分析方法,对RsRARP的学习曲线进行了量化评估,为该手术的培训和推广提供了重要参考。

Developing an efficient and visible prime editing system to restore tobacco 8-hydroxy-copalyl diphosphate gene for labdane diterpene Z-abienol biosynthesis

Prime editing(PE)is a versatile CRISPR-Cas based precise genome-editing platform widely used to introduce a range of possible base conversions in various organisms.However,no PE systems have been shown to induce heritable mutations in tobacco,nor in any other dicot.In this study,we generated an efficient PE system in tobacco that not only introduced heritable mutations,but also enabled anthocyanin-based reporter selection of transgene-free T_(1) plants.This system was used to confer Zabienol biosynthesis in the allotetraploid tobacco cultivar HHDJY by restoring a G>T conversion in the NtCPS2 gene.High levels of Z-abienol were detected in the leaves of homozygous T_(1) plants at two weeks after topping.This study describes an advance in PE systems and expands genome-editing toolbox in tobacco,even in dicots,for use in basic research and molecular breeding.And restoring biosynthesis of Z-abienol in tobacco might provide an efficient way to obtain Z-abienol in plants.

Discriminated sgRNAs-Based SurroGate System Greatly Enhances the Screening Efficiency of Plant Base-Edited Cells

The development of CRISPR/Cas9-mediated base editing has made genomic modification more efficient. However, selection of genetically modified cells from millions of treated cells, especially plant cells, is still challenging. In this study, an efficient surrogate reporter system based on a defective hygromycin resistance gene was established in rice to enrich base-edited cells. After step-by-step optimization, the Discriminated sgRNAs-based SurroGate system (DisSUGs) was established by artificially differentiating the editing abilities of a wild-type single guide RNA (sgRNA) targeting the surrogate reporter gene and an enhanced sgRNA targeting endogenous sites. The DisSUGs enhanced the efficiency of screening base-edited cells by 3- to 5-fold for a PmCDA1-based cytosine-to-tyrosine base editor (PCBE), and 2.5- to 6.5-fold for an adenine base editor (ABE) at endogenous targets. These targets showed editing efficiencies of <25% in the conventional systems. The DisSUGs greatly enhanced the frequency of homozygous substitutions and expanded the activity window slightly for both a PCBE and an ABE. Analyses of the total number of single-nucleotide variants from whole-genome sequencing revealed that, compared with the no-enrichment PCBE strategy, the DisSUGs did not alter the frequency of genome-wide sgRNA-independent off-target mutations, but slightly increased the frequency of target-dependent off-target mutations. Collectively, the DisSUGs developed in this study greatly enhances the efficiency of screening plant base-edited cells and will be a useful system in future applications.

Versatile Nucleotides Substitution in Plant Using an Improved Prime Editing System

Dear Editor,Base editors(BEs)based on the CRISPR/Cas9 system,including cytosine base editors and adenine base editors,which can efficiently perform four transition mutations(C·G-to-T·A and A·T-to-G·C),have been well studied and widely used to produce base mutations in a variety of organisms,including in plants such as rice.

Expanding base editing scope to near-PAMless with engineered CRISPR/Cas9 variants in plants

Dear Editor,Base editors(BEs),including cytosine base editor(CBE)and adenine base editor(ABE),have been widely used to generate irreversible nucleotide substitution in plants and animals.However,their wide applications are largely hindered by the strict NG protospacer adjacent motif(PAM)sequences recognized by Streptococcus pyogenes Cas9(SpCas9)and its engineered variants,such as SpCas9-NG and xCas9(Hua et al.,2019;Ren et al.,2019;Wu et al.,2019;Zhong et al.,2019;Zhang et al.,2020).Most recently,it was reported that three new SpCas9 variants,SpCas9-NRRH,SpCas9-NRTH,and SpCas9-NRCH,could recognize non-G PAMs(NRNH,where R is A or G and H is A,C,or T)in human cells(Miller et al.,2020).Meanwhile,SPRY,another new SpCas9 variant,was developed to greatly expand the editing scope of BEs to nearly PAMless(Walton et al.,2020).In this study,we generated a series of efficient BE toolkits and almost achieved C-to-T mutation without PAM restriction except for NTG PAM,and largely expanded A-to-G mutation scope in stable transformed rice,providing a reference for application in other plants.

The lncRNA39896–miR166b–HDZs module affects tomato resistance to Phytophthora infestans

The yield and quality of tomatoes(Solanum lycopersicum)is seriously affected by Phytophthora infestans.The long non-coding RNA(lnc RNA)Sl-lnc RNA39896 is induced after P.infestans infection and was previously predicted to act as an endogenous target mimic(eTM)for the micro RNA Sl-miR166b,which function in stress responses.Here,we further examined the role of Sl-lncRNA39896 and Sl-mi R166b in tomato resistance to P.infestans.Sl-miR166b levels were higher in Sl-lnc RNA39896-knockout mutants than in wild-type plants,and the mutants displayed enhanced resistance to P.infestans.A six-point mutation in the region of Sl-lncRNA39896 that binds to Sl-miR166b disabled the interaction,suggesting that Sl-lnc RNA39896 acts as an e TM for Sl-mi R166b.Overexpressing Sl-miR166b yielded a similar phenotype to that produced by Sl-lncRNA39896-knockout,whereas silencing of Sl-mi R166b impaired resistance.We verified that Sl-miR166b cleaved transcripts of its target classⅢhomeodomain-leucine zipper genes Sl HDZ34and Sl HDZ45.Silencing of Sl HDZ34/45 decreased pathogen accumulation in plants infected with P.infestans.Additionally,jasmonic acid and ethylene contents were elevated following infection in the plants with enhanced resistance.Sl-lnc RNA39896is the first known lnc RNA to negatively regulate resistance to P.infestans in tomato.We propose a novel mechanism in which the lnc RNA39896–mi R166b–HDZ module modulates resistance to P.infestans.

Configuration and operation combined optimization for EV battery swapping station considering PV consumption bundling

Integration of electric vehicles(EVs),demand response and renewable energy will bring multiple opportunities for low carbon power system.A promising integration will be EV battery swapping station(BSS)bundled with PV(photovoltaic)power.Optimizing the configuration and operation of BSS is the key problem to maximize benefit of this integration.The main objective of this paper is to solve infrastructure configuration of BSS.The principle challenge of such an objective is to enhance the swapping ability and save corresponding investment and operation cost under uncertainties of PV generation and swapping demand.Consequently this paper mainly concentrates on combining operation optimization with optimal investment strategies for BSS considering multiscenarios PV power generation and swapping demand.A stochastic programming model is developed by using state flow method to express different states of batteries and its objective is to maximize the station’s net profit.The model is formulated as a mixed-integer linear program to guarantee the efficiency and stability of the optimization.Case studies validate the effectiveness of the proposed approach and demonstrate that ignoring the uncertainties of PV generation and swapping demand may lead to an inappropriate batteries,chargers and swapping robots configuration for BSS.

Exhumation of deeply subducted crust:Review and outlook

The discovery of ultrahigh-pressure(UHP)index minerals such as coesite and micro-diamond in supracrustal rocks indicate that a large amount of crustal rocks were subducted to mantle depths and subsequently returned to the Earth’s surface.However,exhumation mechanism of the deeply subducted crustal rocks has been a hot topic in geodynamic community and remains controversial.Previous studies have been performed by petrologic observations,analogue experiments and numerical simulations for exhumation processes and mechanisms of deeply subducted crustal rocks,and a series of important results have been achieved.In this paper,we summerize in detail recent progresses and existing problems on types of subduction zones,exhumation processes and mechanisms of deeply subducted crustal rocks,and related factors.Based on these,three forthcoming prospects are presented:(1)The geological processes within the exhuming crust;(2)the interaction between the exhuming crust and the surface process;(3)the interaction between the exhuming crust and the mantle.

Protein-protein interaction analysis in crude bacterial lysates using combinational method of ^19F site-specific incorporation and ^19F NMR

Protein-protein interactions （PPI） are essential for a variety of cellular functions. Many PPI analyses were conducted in vitro, using purified proteins. In this report, the unnatural amino acid tfmF was site-specifically incorporated into several different sites of two Phox-Beml （PB1） domains from two mitogen activated protein kinases （MEKK3 and/ or MEK5） in the E. coil cells.

Erratum to： Protein-protein interaction analysis in crude bacterial lysates using combinational method of ^19F site-specific incorporation and ^19F NMR

ERRATUM TO： PROTEIN CELL 2017, 8（2）：149-154 DOI 10.1007/S13238-016-0336-8In the original publication of this article the correspondence authors＇ e-mail has been missed out. The missing e-mail addresses are provided in this erratum.OPEN ACCESS This article is distributed under the terms of the Creative Commons Attribution 4.0 international License （http：//creativecommons.org/ licenses/by/4.0/）, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author（s） and the source, provide a link to the Creative Commons license, and indicate if changes were made.