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Molecular tuning of CO2-to-ethylene conversion 期刊论文
NATURE, 2020, 577 (7791) : 509-+
作者:  Li, Fengwang;  39;Brien, Colin P.
收藏  |  浏览/下载:11/0  |  提交时间:2020/07/03

The electrocatalytic reduction of carbon dioxide, powered by renewable electricity, to produce valuable fuels and feedstocks provides a sustainable and carbon-neutral approach to the storage of energy produced by intermittent renewable sources(1). However, the highly selective generation of economically desirable products such as ethylene from the carbon dioxide reduction reaction (CO2RR) remains a challenge(2). Tuning the stabilities of intermediates to favour a desired reaction pathway can improve selectivity(3-5), and this has recently been explored for the reaction on copper by controlling morphology(6), grain boundaries(7), facets(8), oxidation state(9) and dopants(10). Unfortunately, the Faradaic efficiency for ethylene is still low in neutral media (60 per cent at a partial current density of 7 milliamperes per square centimetre in the best catalyst reported so far(9)), resulting in a low energy efficiency. Here we present a molecular tuning strategy-the functionalization of the surface of electrocatalysts with organic molecules-that stabilizes intermediates for more selective CO2RR to ethylene. Using electrochemical, operando/in situ spectroscopic and computational studies, we investigate the influence of a library of molecules, derived by electro-dimerization of arylpyridiniums(11), adsorbed on copper. We find that the adhered molecules improve the stabilization of an '  atop-bound'  CO intermediate (that is, an intermediate bound to a single copper atom), thereby favouring further reduction to ethylene. As a result of this strategy, we report the CO2RR to ethylene with a Faradaic efficiency of 72 per cent at a partial current density of 230 milliamperes per square centimetre in a liquid-electrolyte flow cell in a neutral medium. We report stable ethylene electrosynthesis for 190 hours in a system based on a membrane-electrode assembly that provides a full-cell energy efficiency of 20 per cent. We anticipate that this may be generalized to enable molecular strategies to complement heterogeneous catalysts by stabilizing intermediates through local molecular tuning.


Electrocatalytic reduction of CO2 over copper can be made highly selective by '  tuning'  the copper surface with adsorbed organic molecules to stabilize intermediates for carbon-based fuels such as ethylene


  
Lactonization as a general route to beta-C(sp(3))-H functionalization 期刊论文
NATURE, 2020, 577 (7792) : 656-+
作者:  Washington, Harriet A.
收藏  |  浏览/下载:17/0  |  提交时间:2020/07/03

Functionalization of the beta-C-H bonds of aliphatic acids is emerging as a valuable synthetic disconnection that complements a wide range of conjugate addition reactions(1-5). Despite efforts for beta-C-H functionalization in carbon-carbon and carbon-heteroatom bond-forming reactions, these have numerous crucial limitations, especially for industrial-scale applications, including lack of mono-selectivity, use of expensive oxidants and limited scope(6-13). Notably, the majority of these reactions are incompatible with free aliphatic acids without exogenous directing groups. Considering the challenge of developing C-H activation reactions, it is not surprising that achieving different transformations requires independent catalyst design and directing group optimizations in each case. Here we report a Pd-catalysed beta-C(sp(3))-H lactonization of aliphatic acids enabled by a mono-N-protected beta-amino acid ligand. The highly strained and reactive beta-lactone products are versatile linchpins for the mono-selective installation of diverse alkyl, alkenyl, aryl, alkynyl, fluoro, hydroxyl and amino groups at the beta position of the parent acid, thus providing a route to many carboxylic acids. The use of inexpensive tert-butyl hydrogen peroxide as the oxidant to promote the desired selective reductive elimination from the Pd(IV) centre, as well as the ease of product purification without column chromatography, render this reaction amenable to tonne-scale manufacturing.


  
Dietary modifications for enhanced cancer therapy 期刊论文
NATURE, 2020, 579 (7800) : 507-517
作者:  Keller, Matthew D.;  Ching, Krystal L.;  Liang, Feng-Xia;  Dhabaria, Avantika;  Tam, Kayan;  Ueberheide, Beatrix M.;  Unutmaz, Derya;  Torres, Victor J.;  Cadwell, Ken
收藏  |  浏览/下载:17/0  |  提交时间:2020/07/03

Tumours depend on nutrients supplied by the host for their growth and survival. Modifications to the host'  s diet can change nutrient availability in the tumour microenvironment, which might represent a promising strategy for inhibiting tumour growth. Dietary modifications can limit tumour-specific nutritional requirements, alter certain nutrients that target the metabolic vulnerabilities of the tumour, or enhance the cytotoxicity of anti-cancer drugs. Recent reports have suggested that modification of several nutrients in the diet can alter the efficacy of cancer therapies, and some of the newest developments in this quickly expanding field are reviewed here. The results discussed indicate that the dietary habits and nutritional state of a patient must be taken into account during cancer research and therapy.


  
Lipid availability determines fate of skeletal progenitor cells via SOX9 期刊论文
NATURE, 2020
作者:  Obata, Yuuki;  Castano, Alvaro;  Boeing, Stefan;  Bon-Frauches, Ana Carina;  Fung, Candice;  Fallesen, Todd;  De Aguero, Mercedes Gomez;  Yilmaz, Bahtiyar;  Lopes, Rita;  Huseynova, Almaz;  Horswell, Stuart;  Maradana, Muralidhara Rao;  Boesmans, Werend;  Vanden Berghe, Pieter;  Murray, Andrew J.;  Stockinger, Brigitta;  Macpherson, Andrew J.;  Pachnis, Vassilis
收藏  |  浏览/下载:26/0  |  提交时间:2020/07/03

Lipid starvation results in skeletal progenitors favouring commitment to chondrogenic over osteogenic fate, a process mediated by FOXO transcription factors and SOX9.


The avascular nature of cartilage makes it a unique tissue(1-4), but whether and how the absence of nutrient supply regulates chondrogenesis remain unknown. Here we show that obstruction of vascular invasion during bone healing favours chondrogenic over osteogenic differentiation of skeletal progenitor cells. Unexpectedly, this process is driven by a decreased availability of extracellular lipids. When lipids are scarce, skeletal progenitors activate forkhead box O (FOXO) transcription factors, which bind to the Sox9 promoter and increase its expression. Besides initiating chondrogenesis, SOX9 acts as a regulator of cellular metabolism by suppressing oxidation of fatty acids, and thus adapts the cells to an avascular life. Our results define lipid scarcity as an important determinant of chondrogenic commitment, reveal a role for FOXO transcription factors during lipid starvation, and identify SOX9 as a critical metabolic mediator. These data highlight the importance of the nutritional microenvironment in the specification of skeletal cell fate.


  
Glucagon stimulates gluconeogenesis by INSP3R1-mediated hepatic lipolysis 期刊论文
NATURE, 2020, 579 (7798) : 279-+
作者:  Liu, Xiaomeng;  Gao, Hongyan;  Ward, Joy E.;  Liu, Xiaorong;  Yin, Bing;  Fu, Tianda;  Chen, Jianhan;  Lovley, Derek R.;  Yao, Jun
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/03

Although it is well-established that reductions in the ratio of insulin to glucagon in the portal vein have a major role in the dysregulation of hepatic glucose metabolism in type-2 diabetes(1-3), the mechanisms by which glucagon affects hepatic glucose production and mitochondrial oxidation are poorly understood. Here we show that glucagon stimulates hepatic gluconeogenesis by increasing the activity of hepatic adipose triglyceride lipase, intrahepatic lipolysis, hepatic acetyl-CoA content and pyruvate carboxylase flux, while also increasing mitochondrial fat oxidation-all of which are mediated by stimulation of the inositol triphosphate receptor 1 (INSP3R1). In rats and mice, chronic physiological increases in plasma glucagon concentrations increased mitochondrial oxidation of fat in the liver and reversed diet-induced hepatic steatosis and insulin resistance. However, these effects of chronic glucagon treatment-reversing hepatic steatosis and glucose intolerance-were abrogated in Insp3r1 (also known as Itpr1)-knockout mice. These results provide insights into glucagon biology and suggest that INSP3R1 may represent a target for therapies that aim to reverse nonalcoholic fatty liver disease and type-2 diabetes.


  
Synthesis of rare sugar isomers through site-selective epimerization 期刊论文
NATURE, 2020: 403-+
作者:  Jackson, Hartland W.;  Fischer, Jana R.;  Zanotelli, Vito R. T.;  Ali, H. Raza;  Mechera, Robert;  Soysal, Savas D.;  Moch, Holger;  Muenst, Simone;  Varga, Zsuzsanna;  Weber, Walter P.;  Bodenmiller, Bernd
收藏  |  浏览/下载:15/0  |  提交时间:2020/07/03

Glycans have diverse physiological functions, ranging from energy storage and structural integrity to cell signalling and the regulation of intracellular processes(1). Although biomass-derived carbohydrates (such as d-glucose, d-xylose and d-galactose) are extracted on commercial scales, and serve as renewable chemical feedstocks and building blocks(2,3), there are hundreds of distinct monosaccharides that typically cannot be isolated from their natural sources and must instead be prepared through multistep chemical or enzymatic syntheses(4,5). These '  rare'  sugars feature prominently in bioactive natural products and pharmaceuticals, including antiviral, antibacterial, anticancer and cardiac drugs(6,7). Here we report the preparation of rare sugar isomers directly from biomass carbohydrates through site-selective epimerization reactions. Mechanistic studies establish that these reactions proceed under kinetic control, through sequential steps of hydrogen-atom abstraction and hydrogen-atom donation mediated by two distinct catalysts. This synthetic strategy provides concise and potentially extensive access to this valuable class of natural compounds.


Various rare sugars that cannot be isolated from natural sources are synthesized using light-driven epimerization, a process which may find application in other synthetic scenarios.


  
Gram-scale bottom-up flash graphene synthesis 期刊论文
NATURE, 2020, 577 (7792) : 647-651
作者:  Long, Haizhen;  Zhang, Liwei;  Lv, Mengjie;  Wen, Zengqi;  Zhang, Wenhao;  Chen, Xiulan;  Zhang, Peitao;  Li, Tongqing;  Chang, Luyuan;  Jin, Caiwei;  Wu, Guozhao;  Wang, Xi;  Yang, Fuquan;  Pei, Jianfeng;  Chen, Ping;  Margueron, Raphael;  Deng, Haiteng;  Zhu, Mingzhao;  Li, Guohong
收藏  |  浏览/下载:13/0  |  提交时间:2020/07/03

Most bulk-scale graphene is produced by a top-down approach, exfoliating graphite, which often requires large amounts of solvent with high-energy mixing, shearing, sonication or electrochemical treatment(1-3). Although chemical oxidation of graphite to graphene oxide promotes exfoliation, it requires harsh oxidants and leaves the graphene with a defective perforated structure after the subsequent reduction step(3,4). Bottom-up synthesis of high-quality graphene is often restricted to ultrasmall amounts if performed by chemical vapour deposition or advanced synthetic organic methods, or it provides a defect-ridden structure if carried out in bulk solution(4-6). Here we show that flash Joule heating of inexpensive carbon sources-such as coal, petroleum coke, biochar, carbon black, discarded food, rubber tyres and mixed plastic waste-can afford gram-scale quantities of graphene in less than one second. The product, named flash graphene (FG) after the process used to produce it, shows turbostratic arrangement (that is, little order) between the stacked graphene layers. FG synthesis uses no furnace and no solvents or reactive gases. Yields depend on the carbon content of the source  when using a high-carbon source, such as carbon black, anthracitic coal or calcined coke, yields can range from 80 to 90 per cent with carbon purity greater than 99 per cent. No purification steps are necessary. Raman spectroscopy analysis shows a low-intensity or absent D band for FG, indicating that FG has among the lowest defect concentrations reported so far for graphene, and confirms the turbostratic stacking of FG, which is clearly distinguished from turbostratic graphite. The disordered orientation of FG layers facilitates its rapid exfoliation upon mixing during composite formation. The electric energy cost for FG synthesis is only about 7.2 kilojoules per gram, which could render FG suitable for use in bulk composites of plastic, metals, plywood, concrete and other building materials.


Flash Joule heating of inexpensive carbon sources is used to produce gram-scale quantities of high-quality graphene in under a second, without the need for a furnace, solvents or reactive gases.


  
Redox-switchable carboranes for uranium capture and release 期刊论文
NATURE, 2020, 577 (7792) : 652-+
作者:  Marques, Joao C.;  Li, Meng;  Schaak, Diane;  Robson, Drew N.;  Li, Jennifer M.
收藏  |  浏览/下载:31/0  |  提交时间:2020/07/03

The uranyl ion (UO22+  U(vi) oxidation state) is the most common form of uranium found in terrestrial and aquatic environments and is a central component in nuclear fuel processing and waste remediation efforts. Uranyl capture from either seawater or nuclear waste has been well studied and typically relies on extremely strong chelating/binding affinities to UO22+ using chelating polymers(1,2), porous inorganic(3-5) or carbon-based(6,7) materials, as well as homogeneous(8) compounds. By contrast, the controlled release of uranyl after capture is less established and can be difficult, expensive or destructive to the initial material(2,9). Here we show how harnessing the redox-switchable chelating and donating properties of an ortho-substituted closo-carborane (1,2-(Ph2PO)(2)-1,2-C2B10H10) cluster molecule can lead to the controlled chemical or electrochemical capture and release of UO22+ in monophasic (organic) or biphasic (organic/aqueous) model solvent systems. This is achieved by taking advantage of the increase in the ligand bite angle when the closo-carborane is reduced to the nido-carborane, resulting in C-C bond rupture and cage opening. The use of electrochemical methods for uranyl capture and release may complement existing sorbent and processing systems.


Redox-switchable chelation is demonstrated for a carborane cluster molecule, leading to controlled chemical or electrochemical capture and release of uranyl in monophasic or biphasic model solvent systems.


  
Multivalent anions as universal latent electron donors 期刊论文
NATURE, 2019, 573 (7775) : 519-+
作者:  Tang, Cindy G.;  Syafiqah, Mazlan Nur;  Koh, Qi-Mian;  Zhao, Chao;  Zaini, Jamal;  Seah, Qiu-Jing;  Cass, Michael J.;  Humphries, Martin J.;  Grizzi, Ilaria;  Burroughes, Jeremy H.;  Png, Rui-Qi;  Chua, Lay-Lay;  Ho, Peter K. H.
收藏  |  浏览/下载:13/0  |  提交时间:2019/11/27
Secondary organic aerosol reduced by mixture of atmospheric vapours 期刊论文
NATURE, 2019, 565 (7741) : 587-593
作者:  McFiggans, Gordon;  Mentel, Thomas F.;  Wildt, Juergen;  Pullinen, Iida;  Kang, Sungah;  Kleist, Einhard;  Schmitt, Sebastian;  Springer, Monika;  Tillmann, Ralf;  Wu, Cheng;  Zhao, Defeng;  Hallquist, Mattias;  Faxon, Cameron;  Le Breton, Michael;  Hallquist, Asa M.;  Simpson, David;  Bergstrom, Robert;  Jenkin, Michael E.;  Ehn, Mikael;  Thornton, Joel A.;  Alfarra, M. Rami;  Bannan, Thomas J.;  Percival, Carl J.;  Priestley, Michael;  Topping, David;  Kiendler-Scharr, Astrid
收藏  |  浏览/下载:11/0  |  提交时间:2019/11/27