真核基因启动子非依赖的功能转录延伸复合物的体外组装(英文)

真核生物RNA聚合酶Ⅱ的持续合成能力对基因转录过程中每一个阶段,包括启动子脱离、转录暂停、转录终止以及转录偶联DNA损伤修复过程的调节至关重要.在RNA聚合酶Ⅱ介导的转录延伸过程中,其和模板DNA及转录产物RNA紧密结合,形成一个非常稳定的延伸三维复合物(elongationcomplex,EC).此特征性“泡”状结构的形成是RNA聚合酶Ⅱ持续合成能力所必需的.在不依赖启动子及众多转录起始因子的条件下,利用人工合成的RNA与DNA寡核苷酸,在体外组装形成具有功能转录活性的延伸复合物.结果表明,长度为9个核苷酸的RNA与模板DNA形成的杂合分子对转录延伸复合物的形成是必需的,而非转录模板DNA链的加入导致最终活性转录“泡”状复合物的形成,并可转录形成与模板相关的转录产物,进一步通过在模板DNA的特定位置引入一个乙酰氧乙酰氨基芴修饰基团,可特异性地阻断转录延伸过程,从而显示该系统在研究真核基因转录及转录偶联DNA损伤修复机制中的潜在应用价值.

Enhanced stability of highly-dispersed copper catalyst supported by hierarchically porous carbon for long term selective hydrogenation

Copper based catalysts have high potential for the substituent of noble-metal based catalysts as their high selectivity and moderate activity for selective hydrogenation reaction;however,achieving further high catalytic stability is very difficult.In this work,the carbonization process of Cu-based organic frameworks was explored for the synthesis of highly-dispersed Cu supported by hierarchically porous carbon with high catalytic performance for selective hydrogenation of 1,3-butadiene.The porous hierarchy of carbon support and the dispersion of copper nanoparticles can be precisely tuned by controlling the carbonization process.The resultant catalyst carbonized at 600°C exhibits a rather low reaction temperature at 75°C for 100%butadiene conversion with 100%selectivity to butenes,due to its reasonable porous hierarchy and highly-dispersed copper sites.More importantly,unprecedentedly stability of the corresponding Cu catalyst was firstly observed for selective 1,3-butadiene hydrogenation,with both 100%butadiene conversion and 100%butenes selectivity over 120 h of reaction at 75°C.This study verifies that a simply control the carbonization process of metal organic frameworks can be an effective way to obtain Cu-based catalysts with superior catalytic performance for selective hydrogenation reaction.

Hydrophilic bi-functional B-doped g-C_(3)N_(4) hierarchical architecture for excellent photocatalytic H_(2)O_(2) production and photoelectrochemical water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has attracted great interest in photocatalysis and photoelectrocatalysis.However,their poor hydrophilicity poses a great challenge for their applications in aqueous environment.Here,we demonstrate synthesis of a hydrophilic bi-functional hierarchical architecture by the assembly of B-doped g-C_(3)N_(4)nanoplatelets.Such hierarchical B-doped g-C_(3)N_(4)material enables full utilization of their highly enhanced visible light absorption and photogenerated carrier separation in aqueous medium,leading to an excellent photocatalytic H_(2)O_(2)production rate of 4240.3μM g^(-1)h^(-1),2.84,2.64 and 2.13 times higher than that of the bulk g-C_(3)N_(4),g-C_(3)N_(4)nanoplatelets and bulk B doped g-C_(3)N_(4),respectively.Photoanodes based on these hierarchical architectures can generate an unprecedented photocurrent density of 1.72 m A cm^(-2)at 1.23 V under AM 1.5 G illumination for photoelectrochemical water splitting.This work makes a fundamental improvement towards large-scale exploitation of highly active,hydrophilic and stable metal-free g-C_(3)N_(4)photocatalysts for various practical applications.

双功能Cu-TiO_(2)/CuO光催化剂用于大规模协同处理含有机污染物和重金属离子的废水

大多数所制备的光催化剂通常只用于单一地降解有机污染物或还原Cr(VI)的光催化.然而,无机和有机污染物通常共存于工业污水中.同时消除混合的无机和有机污染物仍然存在着巨大的挑战.在本文中,我们通过原位掺杂和异质结工程策略,制备出了新型的双功能CuTiO_(2)/CuO光催化剂用于大规模高效协同光催化消除废水中的有机污染物和过渡金属离子.具体而言,这种双功能光催化剂在RhB和Cr(VI)共存溶液中的光催化RhB降解率和Cr(VI)还原率分别是在单一RhB或Cr(VI)污染物溶液中对应值的2.35和3.84倍.光催化染料分子降解和Cr(VI)还原之间存在显著增强的协同效应.此外,该双功能光催化剂在大规模光催化消除混合污染物方面也表现出较好的活性和稳定性.理论计算表明,铜掺杂和异质结工程促进了高效的光吸收、增高的载流子密度以及快速的光生载流子转移,从而产生高效的协同光催化作用.这种双功能光催化剂的概念为大规模工业废水处理和净化开辟了新途径.

Three-dimensionally ordered macroporous materials for pollutants abatement,environmental sensing and bacterial inactivation

Owing to their facile reactants migration channels,large surface area,maximized exposure of reaction sites and efficient light utilization,three-dimensionally ordered macroporous(3DOM)materials have been extensively adopted in environmental fields such as pollutants removal,environmental detection as well as bacterial disinfection.In this review,the up-to-date 3DOM materials,the corresponding synthesis protocols and the related environmental applications involving photo/electrocatalytic pollutants decomposition,thermocatalytic volatile organic compounds(VOCs)elimination,hazardous substances sensing and bacteria inactivation are completely presented.Simultaneously,the inherent advantages and mechanisms of 3DOM materials in different environmental utilization are thoroughly demonstrated and summarized.Furthermore,the improved performance of environmental applications and the methods of fabricating 3DOM materials are correlated in depth,being favorable for readers to obtain the fundamental knowledge and to motivate some innovative thoughts for modifying 3DOM materials with further elevated environmental remediation capability.Finally,the current difficulties and prospects of 3DOM materials for large-scale and commercial applications are outlooked.This critical review is anticipated to promote the optimization of 3DOM materials and to ripen the related environmental remediation techniques.

My Journey to DNA Repair

I completed my medical studies at the Karolinska Institute in Stockholm but have always been devoted to basic research. My longstanding interest is to understand fundamental DNA repair mechanisms in the fields of cancer therapy, inherited human genetic disorders and ancient DNA. I initially measured DNA decay, including rates of base loss and cytosine deamination. I have dis- covered several important DNA repair proteins and determined their mechanisms of action. The discovery of uracil-DNA glycosylase defined a new category of repair enzymes with each specialized for different types of DNA damage. The base excision repair pathway was first reconstituted with human proteins in my group. Cell-free analysis for mammalian nucleotide excision repair of DNA was also developed in my laboratory. I found multiple distinct DNA ligases in mammalian cells, and led the first genetic and biochemical work on DNA ligases I, III and IV. I discovered the mam- malian exonucleases DNase III （TREX1） and IV （FEN1）. Interestingly, expression of TREXI was altered in some human autoimmune diseases. I also showed that the mutagenic DNA adduct O6-methylguanine （O6mG） is repaired without removing the guanine from DNA, identifying a sur- prising mechanism by which the methyl group is transferred to a residue in the repair protein itself. A further novel process of DNA repair discovered by my research group is the action of AlkB as an iron-dependent enzyme carrying out oxidative demethylation.

The effect of hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios on its pore structure and catalytic performance

Hierarchical single-crystal ZSM-5 zeolites with different Si/Al ratios(Hier-ZSM-5-x,where x=50,100,150 and 200)were synthesized using an ordered mesoporous carbon-silica composite as hard template.Hier-ZSM-5-x exhibits improved mass transport properties,excellent mechanical and hydrothermal stability,and higher catalytic activity than commercial bulk zeolites in the benzyl alcohol self-etherification reaction.Results show that a decrease in the Si/Al ratio in hierarchical single-crystal ZSM-5 zeolites leads to a significant increase in the acidity and the density of micropores,which increases the final catalytic conversion.The effect of porous hierarchy on the diffusion of active sites and the final catalytic activity was also studied by comparing the catalytic conversion after selectively designed poisoned acid sites.These poisoned Hier-ZSM-5-x shows much higher catalytic conversion than the poisoned commercial ZSM-5 zeolite,which indicates that the numerous intracrystalline mesopores significantly reduce the diffusion path of the reactant,leading to the faster diffusion inside the zeolite to contact with the acid sites in the micropores predominating in ZSM-5 zeolites.This study can be extended to develop a series of hierarchical single-crystal zeolites with expected catalytic performance.

Template-free synthesis of hierarchically macro-mesoporous Mn-TiO2 catalysts for selective reduction of NO with NH3

This study described a template-flee method for the synthesis of hierarchically macro-mesoporous Mn- TiO2 catalysts. The promoting effect of Mn doping and the hierarchically macro-mesoporous architecture on TiO2 based catalysts was also investigated for the selective reduction of NO with NH3. The results show that the catalytic performance of TiO2 based catalysts was improved greatly after Mn doping. Meanwhile, the Mn- TiO2 catalyst with the hierarchically macro-mesoporous architecture has a better catalytic activity than that without such an architecture.

Maintenance of Genome Stability

It was ever thought that genomic information is transmitted faithfully from generation to generation. But our current knowledge does not indicate that it is the case. For example, genomic variations can be generated from DNA replication infidelity and unequal chromosome segregation. Natural decay of DNA molecules is also a fundamental source of changing genomic information. In addition, cellular and organismal exposure to exogenous genotoxic agents such as ultraviolet （UV） light, oxidative stress, chemical mutagens, and radiation can lead to a variety of modifications on DNA constituents, resulting in genome alterations. Fortunately, cells have evolved several response systems to tackle numerous DNA lesions in order to maintain their genome integrity. Among them, check- point control is probably the most well-known one. For exam- ple, checkpoint responds to replication stress, replication fork stalling, double-strand DNA breaks, and various other types of DNA lesions. Increasing experimental evidence indicates that genomic instability is probably the fundamental reason for carcinogenesis. Genomic instability is also found to be a main etiological factor of neurodegenerative diseases, aging, immunodeficiency, etc. Thus, to understand how cells regulate to maintain their genomic stability is of fundamental importance.

Superconducting fault current limiter(SFCL)for fail-safe DC-DC conversion:From power electronic device to micro grid protection

In DC micro grids and networks,DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads.Most of the semiconductor-based devices suffer from poor fault withstanding abilities,but conventional power electronic protection schemes have the bottlenecks of the time-delay,self-malfunction and mis-judgement.This paper presents a novel solution using the superconducting fault current limiter(SFCL)to protect a power electronic device and extend the usage to a micro grid.This SFCL is actually a self-triggering,recoverable,and passive current limiter,which does not involve any additional circuit hardware and software.Experimental investigations and simulation analyses clarify the feasibility of using this superconductor-based protection scheme to implement the self-acting fail-safe protection of DC-DC converters.Further system-level simulations explore the SFCL to suppress the over-current and stabilize the bus voltage of a photovoltaic based DC micro grid,particularly facing millisecond-level transients and faults.Our experimental and theoretical investigations lay some technical bases to establish a superconductor-semiconductor-coupled interdisciplinary application from the view from the applied superconductivity,to power electronics,and to micro grids.