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加拿大发布《2030年减排计划》 快报文章
气候变化快报,2022年第08期
作者:  董利苹
Microsoft Word(16Kb)  |  收藏  |  浏览/下载:848/0  |  提交时间:2022/04/20
Canada  Emissions Reduction Plan  Clean Air  Strong Economy  Next Steps  
美国实施可持续发展目标的步骤建议 快报文章
资源环境快报,2021年第8期
作者:  牛艺博
Microsoft Word(22Kb)  |  收藏  |  浏览/下载:468/0  |  提交时间:2021/04/30
US  SDG  Steps  
One Earth载文提出拯救地球的4个步骤 快报文章
资源环境快报,2021年第3期
作者:  董利苹
Microsoft Word(16Kb)  |  收藏  |  浏览/下载:499/0  |  提交时间:2021/02/15
Four Steps for the Earth  the Post-2020 Global Biodiversity Framework  
DNA-repair enzyme turns to translation 期刊论文
NATURE, 2020, 579 (7798) : 198-199
作者:  Bian, Zhilei;  Gong, Yandong;  Huang, Tao;  Lee, Christopher Z. W.;  Bian, Lihong;  Bai, Zhijie;  Shi, Hui;  Zeng, Yang;  Liu, Chen;  He, Jian;  Zhou, Jie;  Li, Xianlong;  Li, Zongcheng;  Ni, Yanli;  Ma, Chunyu;  Cui, Lei;  Zhang, Rui;  Chan, Jerry K. Y.;  Ng, Lai Guan;  Lan, Yu;  Ginhoux, Florent;  Liu, Bing
收藏  |  浏览/下载:38/0  |  提交时间:2020/07/03

A key DNA-repair enzyme has a surprising role during the early steps in the assembly of ribosomes - the molecular machines that translate the genetic code into protein.


  
A metabolic pathway for bile acid dehydroxylation by the gut microbiome 期刊论文
NATURE, 2020
作者:  Zhong, Miao;  Tran, Kevin;  Min, Yimeng;  Wang, Chuanhao;  Wang, Ziyun;  Dinh, Cao-Thang;  De Luna, Phil;  Yu, Zongqian;  Rasouli, Armin Sedighian;  Brodersen, Peter;  Sun, Song;  Voznyy, Oleksandr;  Tan, Chih-Shan;  Askerka, Mikhail;  Che, Fanglin;  Liu, Min;  Seifitokaldani, Ali;  Pang, Yuanjie;  Lo, Shen-Chuan;  Ip, Alexander;  Ulissi, Zachary;  Sargent, Edward H.
收藏  |  浏览/下载:44/0  |  提交时间:2020/07/03

The biosynthetic pathway that produces the secondary bile acids DCA and LCA in human gut microbes has been fully characterized, engineered into another bacterial host, and used to confer DCA production in germ-free mice-an important proof-of-principle for the engineering of gut microbial pathways.


The gut microbiota synthesize hundreds of molecules, many of which influence host physiology. Among the most abundant metabolites are the secondary bile acids deoxycholic acid (DCA) and lithocholic acid (LCA), which accumulate at concentrations of around 500 mu M and are known to block the growth ofClostridium difficile(1), promote hepatocellular carcinoma(2)and modulate host metabolism via the G-protein-coupled receptor TGR5 (ref.(3)). More broadly, DCA, LCA and their derivatives are major components of the recirculating pool of bile acids(4)  the size and composition of this pool are a target of therapies for primary biliary cholangitis and nonalcoholic steatohepatitis. Nonetheless, despite the clear impact of DCA and LCA on host physiology, an incomplete knowledge of their biosynthetic genes and a lack of genetic tools to enable modification of their native microbial producers limit our ability to modulate secondary bile acid levels in the host. Here we complete the pathway to DCA and LCA by assigning and characterizing enzymes for each of the steps in its reductive arm, revealing a strategy in which the A-B rings of the steroid core are transiently converted into an electron acceptor for two reductive steps carried out by Fe-S flavoenzymes. Using anaerobic in vitro reconstitution, we establish that a set of six enzymes is necessary and sufficient for the eight-step conversion of cholic acid to DCA. We then engineer the pathway intoClostridium sporogenes, conferring production of DCA and LCA on a nonproducing commensal and demonstrating that a microbiome-derived pathway can be expressed and controlled heterologously. These data establish a complete pathway to two central components of the bile acid pool.


  
Extra help for neuron grafts 期刊论文
NATURE, 2020, 582 (7810) : 39-40
作者:  Raz, Mical
收藏  |  浏览/下载:14/0  |  提交时间:2020/07/03

Grafts of stem-cell-derived precursors of dopamine neurons could be used to treat Parkinson'  s disease, but this approach has limitations. Injecting a growth factor three weeks after transplantation can overcome some of these limits.


Steps to improve function and survival of dopamine-neuron transplants.


  
A general carbonyl alkylative amination for tertiary amine synthesis 期刊论文
NATURE, 2020
作者:  Ouyang, David;  He, Bryan;  Ghorbani, Amirata;  Yuan, Neal;  Ebinger, Joseph;  Langlotz, Curtis P.;  Heidenreich, Paul A.;  Harrington, Robert A.;  Liang, David H.;  Ashley, Euan A.;  Zou, James Y.
收藏  |  浏览/下载:26/0  |  提交时间:2020/07/03

The ubiquity of tertiary alkylamines in pharmaceutical and agrochemical agents, natural products and small-molecule biological probes(1,2) has stimulated efforts towards their streamlined synthesis(3-9). Arguably the most robust method for the synthesis of tertiary alkylamines is carbonyl reductive amination(3), which comprises two elementary steps: the condensation of a secondary alkylamine with an aliphatic aldehyde to form an all-alkyl-iminium ion, which is subsequently reduced by a hydride reagent. Direct strategies have been sought for a '  higher order'  variant of this reaction via the coupling of an alkyl fragment with an alkyl-iminium ion that is generated in situ(10-14). However, despite extensive efforts, the successful realization of a '  carbonyl alkylative amination'  has not yet been achieved. Here we present a practical and general synthesis of tertiary alkylamines through the addition of alkyl radicals to all-alkyl-iminium ions. The process is facilitated by visible light and a silane reducing agent, which trigger a distinct radical initiation step to establish a chain process. This operationally straightforward, metal-free and modular transformation forms tertiary amines, without structural constraint, via the coupling of aldehydes and secondary amines with alkyl halides. The structural and functional diversity of these readily available precursors provides a versatile and flexible strategy for the streamlined synthesis of complex tertiary amines.


The synthesis of tertiary amines is achieved through a carbonyl alkylative amination reaction facilitated by visible light, in which an aldehyde and an amine condense to form an iminium ion that subsequently reacts with alkyl radical.


  
The stepwise assembly of the neonatal virome is modulated by breastfeeding 期刊论文
NATURE, 2020
作者:  Medina, Christopher B.;  Mehrotra, Parul;  Arandjelovic, Sanja;  Perrys, Justin S. A.;  Guo, Yizhan;  Morioka, Sho;  Barron, Brady;  Walk, Scott F.;  Ghesquiere, Bart;  Lorenz, Ulrike;  Krupnick, Alexander S.;  Ravichandran, Kodi S.
收藏  |  浏览/下载:47/0  |  提交时间:2020/07/03

The infant gut is colonized first by temperate bacteriophages induced from pioneer bacteria and later by viruses that replicate in human cells, the populations of which are modulated by breastfeeding.


The gut of healthy human neonates is usually devoid of viruses at birth, but quickly becomes colonized, which-in some cases-leads to gastrointestinal disorders(1-4). Here we show that the assembly of the viral community in neonates takes place in distinct steps. Fluorescent staining of virus-like particles purified from infant meconium or early stool samples shows few or no particles, but by one month of life particle numbers increase to 10(9) per gram, and these numbers seem to persist throughout life(5-7). We investigated the origin of these viral populations using shotgun metagenomic sequencing of virus-enriched preparations and whole microbial communities, followed by targeted microbiological analyses. Results indicate that, early after birth, pioneer bacteria colonize the infant gut and by one month prophages induced from these bacteria provide the predominant population of virus-like particles. By four months of life, identifiable viruses that replicate in human cells become more prominent. Multiple human viruses were more abundant in stool samples from babies who were exclusively fed on formula milk compared with those fed partially or fully on breast milk, paralleling reports that breast milk can be protective against viral infections(8-10). Bacteriophage populations also differed depending on whether or not the infant was breastfed. We show that the colonization of the infant gut is stepwise, first mainly by temperate bacteriophages induced from pioneer bacteria, and later by viruses that replicate in human cells  this second phase is modulated by breastfeeding.


  
Control and single-shot readout of an ion embedded in a nanophotonic cavity 期刊论文
NATURE, 2020, 580 (7802) : 201-+
作者:  Rollie, Clare;  Chevallereau, Anne;  Watson, Bridget N. J.;  Chyou, Te-yuan;  Fradet, Olivier;  McLeod, Isobel;  Fineran, Peter C.;  Brown, Chris M.;  Gandon, Sylvain;  Westra, Edze R.
收藏  |  浏览/下载:44/0  |  提交时间:2020/07/03

Distributing entanglement over long distances using optical networks is an intriguing macroscopic quantum phenomenon with applications in quantum systems for advanced computing and secure communication(1,2). Building quantum networks requires scalable quantum light-matter interfaces(1) based on atoms(3), ions(4) or other optically addressable qubits. Solid-state emitters(5), such as quantum dots and defects in diamond or silicon carbide(6-10), have emerged as promising candidates for such interfaces. So far, it has not been possible to scale up these systems, motivating the development of alternative platforms. A central challenge is identifying emitters that exhibit coherent optical and spin transitions while coupled to photonic cavities that enhance the light-matter interaction and channel emission into optical fibres. Rare-earth ions in crystals are known to have highly coherent 4f-4f optical and spin transitions suited to quantum storage and transduction(11-15), but only recently have single rare-earth ions been isolated(16,17) and coupled to nanocavities(18,19). The crucial next steps towards using single rare-earth ions for quantum networks are realizing long spin coherence and single-shot readout in photonic resonators. Here we demonstrate spin initialization, coherent optical and spin manipulation, and high-fidelity single-shot optical readout of the hyperfine spin state of single Yb-171(3+) ions coupled to a nanophotonic cavity fabricated in an yttrium orthovanadate host crystal. These ions have optical and spin transitions that are first-order insensitive to magnetic field fluctuations, enabling optical linewidths of less than one megahertz and spin coherence times exceeding thirty milliseconds for cavity-coupled ions, even at temperatures greater than one kelvin. The cavity-enhanced optical emission rate facilitates efficient spin initialization and single-shot readout with conditional fidelity greater than 95 per cent. These results showcase a solid-state platform based on single coherent rare-earth ions for the future quantum internet.


Single ytterbium ion qubits in nanophotonic cavities have long coherence times and can be optically read out in a single shot, establishing them as excellent candidates for optical quantum networks.


  
REFUGEE CAMPS RACE TO AVERT CORONAVIRUS CATASTROPHE 期刊论文
NATURE, 2020, 581 (7806) : 18-18
作者:  Schewe, Phillip F.
收藏  |  浏览/下载:4/0  |  提交时间:2020/07/03

From Bangladesh to Somalia, researchers and aid workers are taking different steps to protect people among the most vulnerable to the pandemic.


From Bangladesh to Somalia, researchers and aid workers are taking different steps to protect people among the most vulnerable to the pandemic.