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.

CO_(2)作为化学品原料的高效利用途径:与烷烃耦合反应

CO_(2)作为碳资源的规模化高附加值利用是实现其减排的重要方向.然而,由于其热力学稳定,以CO_(2)为原料高效转化为大宗化学品一直是一个巨大的挑战.工业上普遍以富氢的石脑油为原料生产相对缺氢的烯烃和芳烃产品,但其存在原料和目标产品之间的碳氢不平衡问题.理论上,采用CO_(2)与富氢的烷烃耦合,可以改善二者的平衡关系,提高目标产物选择性,同时实现CO_(2)资源化利用.已有研究采用CO_(2)与烷烃反应,将CO_(2)转化为CO并减少氢气的生成,但CO_(2)的碳原子没有进入烃类产物中.本文系统研究了酸性分子筛催化的CO_(2)与烷烃耦合反应,大幅提高了芳烃选择性,证实部分CO_(2)中的碳原子直接进入了芳烃产品中.本文以H-ZSM-5为催化剂,对比研究了正丁烷、正戊烷和正己烷在He和CO_(2)气氛中的转化反应,并详细研究了反应温度、CO_(2)/n-butane比例、接触时间以及分子筛酸量等条件对耦合反应的影响.结果表明,CO_(2)的引入可大幅促进芳烃的生成,同时甲烷和乙烷等小分子烷烃的生成受到抑制.在优化反应条件下,CO_(2)/n-butane比例为0.475时,CO_(2)和n-butane转化率分别可达17.5%和100%,芳烃选择性高达80%.使用^(13)C同位素标记的CO_(2)与n-butane进行耦合反应,发现芳烃产物中含有部分13C同位素标记的碳原子,表明这部分碳原子来自CO_(2)中的碳.对耦合反应后的催化剂进行溶积碳并采用色质谱分析,发现大量甲基取代的内酯和甲基取代的环烯酮等含氧物种.同位素标记实验结果表明,这些含氧中间体由CO_(2)与烃类耦合转化生成.通过设计实验验证了反应途径,即CO_(2)与碳正离子反应得到环内酯,环内酯进一步转化为甲基环烯酮,甲基环烯酮转化为芳烃产物.提出了H-ZSM-5催化CO_(2)与烷烃耦合反应的机理,并采用密度泛函理论计算了耦合反应机理各步骤的能垒,结果验证了耦合反应机理的可行性.综上,本文提出的耦合反应为CO_(2)碳资源的大规模直接利用提供了一条有效的途径,具有广阔的应用前景.

A Combining Call Admission Control and Power Control Scheme for D2D Communications Underlaying Cellular Networks

As device-to-device(D2D) communications usually reuses the resource of cellular networks, call admission control(CAC) and power control are crucial problems. However in most power control schemes, total data rates or throughput are regarded as optimization criterion. In this paper, a combining call admission control(CAC) and power control scheme under guaranteeing QoS of every user equipment(UE) is proposed. First, a simple CAC scheme is introduced. Then based on the CAC scheme, a combining call admission control and power control scheme is proposed. Next, the performance of the proposed scheme is evaluated. Finally, maximum DUE pair number and average transmitting power is calculated. Simulation results show that D2 D communications with the proposed combining call admission control and power control scheme can effectively improve the maximum DUE pair number under the premise of meeting necessary QoS.

A novel miRNA negatively regulates resistance to Glomerella leaf spot by suppressing expression of an NBS gene in apple

Glomerella leaf spot(GLS)of apple(Malus×domestica Borkh.),caused by Glomerella cingulata,is an emerging fungal epidemic threatening the apple industry.Little is known about the molecular mechanism underlying resistance to this devastating fungus.In this study,high-throughput sequencing technology was used to identify microRNAs(miRNAs)involved in GLS resistance in apple.We focused on miRNAs that target genes related to disease and found that expression of a novel miRNA,Md-miRln20,was higher in susceptible apple varieties than in resistant ones.Furthermore,its target gene Md-TN1-GLS exhibited the opposite expression pattern,which suggested that the expression levels of Md-miRln20 and its target gene are closely related to apple resistance to GLS.Furthermore,downregulation of MdmiRln20 in susceptible apple leaves resulted in upregulation of Md-TN1-GLS and reduced the disease incidence.Conversely,overexpression of Md-miRln20 in resistant apple leaves suppressed Md-TN1-GLS expression,with increased disease incidence.We demonstrated that Md-miRln20 negatively regulates resistance to GLS by suppressing Md-TN1-GLS expression and showed,for the first time,a crucial role for miRNA in response to GLS in apple.

Selective exchange of alkali metal ions on EAB zeolite

EAB zeolite was successfully prepared and applied to selective adsorption of Li^(+),Na^(+)and K^(+)ions.The physical and chemical properties of the adsorbent were characterized by X-ray diffraction(XRD),X-ray fluorescence(XRF),scanning electron microscope(SEM)and thermogravimetry(TG)methods.The ion exchange behaviours for Li^(+),Na^(+)and K^(+)ions in monomcomponent and multicomponent solutions were studied.In independent ion exchange,the ion exchange capacities ratiosα(/Na/Li)andα(K/Li)were 3.8 and 6.2,respectively.In competitive ion exchange,the selectivitiesβ(Na/Li)andβ(K/Li)increased with the initial concentrations and reached 409 and 992 when the initial concentrations was 100 mmol/L.The thermodynamic study results showed that Gibbs free energy change(ΔGΘ)of ion exchange reaction between Li-EAB and K^(+)was-34.96 kJ/mol,indicating that ion exchange of K^(+)ions was more energetically favourable than Li^(+)ions.The calculation results showed that the energy barriers of ion exchange increased in the order K^(+)Na^(+)<Li^(+).The study shows that EAB zeolite is potential to be used in the separation of alkali ions.

Methylcyclopentenyl cation mediated reaction route in methanol-to-olefins reaction over H-RUB-50 with small cavity

Methylcyclopentenyl cations(MCP+)have been regarded as active intermediates during methanol conversion,however,their function mode in the reaction are still uncertain.In our recent report,trimethylcyclopentenyl cation(triMCP+)and its deprotonated counterpart(trimethylcyclopentadiene,tri MCP)were directly captured on H-RUB-50 catalyst with small cavity by the aid of in situ 13C MAS NMR spectroscopy,and their higher catalytic reactivity were clarified by 12C/13C-CH3OH isotopic switch experiment.In this contribution,an alternative route-cyclopentadienes-based cycle was applied on methanol conversion catalyzed on the H-RUB-50,in which ethene was produced with the participation of tri MCP+as critical intermediate.Then the cyclopentadienes-based cycle was predicted to be energetically favorable for ethene formation by density functional theory(DFT)calculations.The energetic comparison of paring mechanism in the aromatics-based cycle and cyclopentadienes-based cycle with the involvements of trimethylcyclopentadienyl(tri MCPdi+)and tri MCP+as the corresponding active intermediates suggests that cyclopentadienes-based cycle is a feasible route for ethene formation.Furthermore,this work highlights the importance of the steric constraint and the host-guest interaction induced by the zeolite with cavity structure in the formation of intermediates and reaction pathway.

Genome-wide characterization of graft-transmissible mRNA-coding P450 genes of cucumber(Cucumis sativus L.)

P450(cytochrome P450)is a supergene family,which is involved in various metabolic pathways in plants.Based on previous study,we found some of cucumber P450 mRNAs were systemic mobile in cucumber/pumpkin grafts.However,the reason that why P450 mRNAs were endorsed as signaling,and what specific motif(s)did they harbored is not clear yet.Here,we first identified 221 CsaP450 genes in cucumber genomewide level.Combining with graft-transmissiblemRNAs datasets in cucumber,we elucidated 15mobile-CsaP450-coding genes,of which 5 and 10 belonged to A-type and non-A type respectively.Compared with Arabidopsis and pumpkin(Cucubit moschata)graft-induced-transmissible P450 mRNAs,a phylogenetic treewas constructed and divided into eight clans by usingmultiple-sequence alignment.Gene ontology(GO)enrichment and Kyoto Encyclopedia of Genes and Genomes(KEGG)annotations indicated that the expression patterns of the mobile-mRNA-coding CsaP450 genes in different tissues of cucumber was specifically enriched in oxidoreductase activity and secondary metabolic pathways.The structures and motifs of these 15 mobile-mRNA-coding CsaP450 genes and their types of regulatory elements told that the proportion of CU-rich motifs was higher than nonmobile-mRNA-coding CsaP450 genes.The integrated analysis of mobility direction and mRNA abundance of 15 mobilemRNA-coding CsaP450 genes allowed to conclude that there was rarely relationship between them.The study provided a new insight into the relationship between the motifs and functional characterization of mobile-mRNA-coding P450 genes of cucumber in genome-wide levels.

Efficacy and Safety of Adding and Subtracting Decoction of Rehmanniae Combined with Western Medicine in the Treatment of Hypertension:A Systematic Review and Meta-analysis

Objective:Systematically evaluating the efficacy and safety of adding and subtracting decoction of rehmanniae combined with Western medicine in the treatment of hypertension.Methods:PubMed,The Cochrane Library,EMBASE,Web of Science,CNKI,Wanfang Database,VIP database and China Biomedical Literature Service System(CBM)were searched.All randomized controlled studies(RCTs)on adding and subtracting decoction ofrehmanniae combined with Western medicine in the treatment of hypertension were retrieved.The retrieval period is from the database construction to November 2021.Two investigators independently screened the literature,collected baseline data of patients and data on related indicators,and evaluated the risk of bias in the included randomized controlled trials.Meta-analysis was performed by RevMan5.3 software.Results:Five randomized controlled trials including 380 patients were obtained after screening by inclusing and exclusing criteria.Meta-analysis results showed that:In the experimental group,TCM syndrome score(MD=-4.08,95%CI:-5.32 to-2.84,P<0.00001),systolic blood pressure(SBP)(MD=-7.77,95%CI:-12.03 to-3.51,P=0.0003),diastolic blood pressure(DBP)(MD=-6.76,95%CI:-9.59 to-3.93,P<0.00001)were better than the control group,and the differences were statistically significant.Conclusion:The current evidence shows that compared with the simple use of Western medicine,adding and subtracting decoction of rehmanniae combined with Western medicine in the treatment of hypertension has more advantages in improving TCM syndromes and reducing systolic and diastolic blood pressure,and the conclusion is reliable.However,due to the limited number and low quality of included randomized controlled trials,more randomized,double-blind,large-sample clinical studies are needed to confirm the above conclusions.

Cucumber malate decarboxylase,CsNADP-ME2,functions in the balance of carbon and amino acid metabolism in fruit

Central metabolism produces carbohydrates and amino acids that are tightly correlated to plant growth and thereby crop productivity.Malate is reported to link mitochondrial respiratory metabolism with cytosolic biosynthetic pathways.Although the function of malate metabolism-related enzymes in providing carbon has been characterized in some plants,evidence for this role in the fleshy fruit of cucumber is lacking.Here,radiolabeled bicarbonate fed into the xylem stream from the cucumber roots was incorporated into amino acids,soluble sugars,and organic acids in the exocarp and vasculature of fruits.The activities of decarboxylases,especially decarboxylation from NADP-dependent malic enzyme(NADP-ME),were higher in cucumber fruit than in the leaf lamina.Histochemical localization revealed that CsNADP-ME2 was mainly located in the exocarp and vascular bundle system of fruit.Radiotracer and gas-exchange analysis indicated that overexpression of CsNADP-ME2 could promote carbon flux into soluble sugars and starch in fruits.Further studies combined with metabolic profiling revealed that the downregulation of CsNADP-ME2 in RNA interference(RNAi)lines caused the accumulation of its substrate,malate,in the exocarp.In addition to inhibition of glycolysis-related gene expression and reduction of the activities of the corresponding enzymes,increased amino acid synthesis and decreased sugar abundance were also observed in these lines.The opposite effect was found in CsNADP-ME2-overexpressing lines,suggesting that there may be a continuous bottom-up feedback regulation of glycolysis in cucumber fruits.Overall,our studies indicate that CsNADP-ME2 may play potential roles in both central carbon reactions and amino acid metabolism in cucumber fruits.

Based on network pharmacology to explore the mechanism of nephrotoxicity of Xanthii Fructus

Objective:To explore the potential mechanism of nephrotoxicity induced by Xanthii Fructus(XF)through network pharmacology.Methods:The active ingredients and targets of XF were screened through Traditional Chinese Medicine Systems Pharmacology Database,PubChem Database and Swiss Target Prediction Database,and the related pathogenic genes of nephrotoxicity were downloaded from Genecards,pharmGKB and OMIM databases.The potential target is the intersection of XF and the pathogenic gene of nephrotoxicity.Cytoscape software was used to construct a network of“XF-Potential active ingredient-Target-Nephrotoxicity network”.Protein protein interaction(PPI)network was constructed by String database,and the data was analyzed and sorted out to obtain the key active components and core target proteins of XF.GO functional enrichment analysis and KEGG pathway enrichment analysis of key target proteins were performed by R software.Results:11 active components,167 targets,6839 nephrotoxicity related pathogenic genes and 139 intersection target genes were screened from XF.After constructing the network of“XF-Potential active ingredient-target-nephrotoxicity network”and PPI network,the key active ingredients of XF were identified as Moupinamide,Beta-sitosterol and Stigmasterol,and the core target proteins were CASP3,HSP90AA1 and TP53.There were 2072 GO entries(P<0.05),including 1876 Biological Process(BP),64 Cellular Component(CC)and 132 Molecular Function(MF).KEGG enrichment analysis revealed 138 pathways(P<0.05),mainly involving p53 signaling pathway,IL-17 signaling pathway,PI3K-Akt signaling pathway were strongly correlated with the nephrotoxicity of XF.Conclusion:The core target protein of XF HSP90AA1,CASP3 and TP53 participate in p53 signaling Pathway,PI3K-Akt signaling Pathway,IL-17 signaling Pathway and other pathways to regulate apoptosis and induce inflammatory responses,resulting in kidney damage.

Does the China Railway Express Promote Equitable Regional Development?Evidence from Manufacturing Relocation

The China Railway Express(CRE)has improved regional economic integration with external markets and has reshaped regional development by encouraging the relocation of manufacturing activities("manufacturing transfer").We analyzed data from 284 prefecture-level cities in China to evaluate the impact of the CRE on regional manufacturing relocation,using a staggered difference-in-diferences model with entropy balancing.We found that the launch of the CRE significantly stimulated the relocation of manufacturing industries to node cities-key hubs for transportation and logistics within the CRE network-especially in the central,western,and northeastern regions.Specifically,the CRE significantly increased manufacturing dynamism,firm profitability,openness,and foreign investment in node cities,which attracted more manufacturing industries to relocate in this area.Higher levels of infrastructure development moderated the CRE's effect.Further analysis showed that significant moderating effects of infrastructure development occurred only in the western region.Overall,our conclusions provide useful insights into how to promote equitable regional development through manufacturing development in China.

Y_(4)GeO_(8):Er^(3+),Yb^(3+) up-conversion phosphors for optical temperature sensor based on FIR technique

Herein,we reported novel Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors elaborated via conventional solid-state reaction.and we further explored their properties as optical thermometer by using fluorescence intensity ratio(FIR)method complemented by detailed analysis on crystal structure,up-conversion luminescence and energy transfer from Yb^(3+)to Er^(3+).Upon 980 nm laser excitation,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors present525,547 and 659 nm emission bands assigned to the characteristic transitions of Er^(3+).Furthermore,Y_(4)GeO_(8):Er^(3+),Yb^(3+)samples show outstanding temperature sensing performances.To be specific,the minimal temperature resolution is 0.03 K(303 K),and the relative sensitivity of FIR can be up to 1.152%/K(303 K).Hence,Y_(4)GeO_(8):Er^(3+),Yb^(3+)phosphors can be possible candidates for thermometry devices.

植物标记和非标记定量蛋白质组学技术

蛋白质是细胞中重要的有机大分子,是生命活动的主要执行者.植物在受到外界信号干扰时其主要反应是通过调节细胞内蛋白质的合成和降解来恢复稳态.因而,蛋白质的定量分析有助于人们更深入地揭示植物细胞中蛋白质的动态变化及其分子功能.随着高分辨质谱技术的发展,使用质谱方法对蛋白质进行高通量定量和定性分析的蛋白质组学技术已经成为研究蛋白质功能的重要分析手段,同时也是植物生物学研究领域的热点之一.结合本课题组取得的研究成果,本文总结和概述了植物蛋白质组学定量方法的最新进展,包括非标记定量和稳定同位素标记分析方法,比较不同方法在蛋白定量的精确度、蛋白组覆盖率和稳定性等方面的优缺点,分析其在植物生物学研究中的应用范围,并对这方面的研究热点进行展望.

Transcriptome and genome analysis to identify C2H2 genes participating in low-temperature conditioning-alleviated postharvest chilling injury of peach fruit

Objectives:This work intended to identify candidate C2H2 genes participating in low-temperature conditioning(LTC)-alleviated postharvest chilling injury of peach fruit.Materials and Methods:For LTC treatment,fruit were pre-stored at 10℃for 5 d and then transferred to 0℃storage.Fruit firmness was measured by a hardness tester.H_(2)O_(2)content was determined by luminosity measurement model using a multifunctional enzyme labeler.Identification of C2H2 family members was performed by HMMSCAN according to peach genome.The cis-acting element of gene promoters was analyzed using the Plant CARE website.Weighted gene coexpression network analysis(WGCNA)was performed by the WGCNA package in the BMK Cloud platform.Results:LTC treatment decreased flesh browning rate and H_(2)O_(2)production of‘Beijing No.9’peach.Transcription factor identification of differentially expressed genes in 0℃and the LTC treatment indicated that peach C2H2 participated in the regulation of chilling injury.A total of 47 C2H2 genes were identified based on peach genome.Real-time quantitative polymerase chain reaction(qRT-PCR),phylogenetic analysis and promoter cis-acting element analysis revealed that ZFP21 was involved in the regulation of LTC-alleviated chilling injury in peach.WGCNA and dual luciferase assay suggested that ZFP21 participated in LTC-alleviated chilling injury by downregulating the expression of reactive oxygen species-related genes Rboh.Conclusions:Our investigation,based on genome and RNA-seq,revealed that ZFP21 was involved in LTC treatment-alleviated chilling injury of peach fruit.This work is useful for the identification of peach cold tolerance-related genes and the study of C2H2 family in peach.

The chemistry,stability and health effects of phenolic compounds in cultivated hawthorn(Crataegus pinnatifida var.major):a review

Cultivated hawthorn(Crataegus pinnatifida var.major),the principal cultivated hawthorn species in China,is rich in phenolic compounds.These phytochemicals are considered essential bioactive ingredients in different organs of cultivated hawthorn,contributing to its health effects.However,there is lack of a comprehensive review that systematically summarizes the chemistry,health effects,and stability of phenolic substances.This review summarizes recent progress in the characterization,classification,and distribution of phenolic compounds in C.pinnatifida var.major,including procyanidins,flavonoids,phenolic acids,lignans,and others.Importantly,the stability of these compounds was found to be influenced by factors such as the hawthorn development process,postharvest storage,postharvest processing,and the gastrointestinal tract environment.Additionally,the health effects of phenolic compounds in cultivated hawthorn and their underlying mechanisms were discussed.This review provides valuable insights into the utilization of hawthorn resources and the development of the hawthorn industry.