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Structure and catalytic mechanism of a human triacylglycerol-synthesis enzyme 期刊论文
NATURE, 2020, 581 (7808) : 323-+
作者:  Nikoo, Mohammad Samizadeh;  Jafari, Armin;  Perera, Nirmana;  Zhu, Minghua;  Santoruvo, Giovanni;  Matioli, Elison
收藏  |  浏览/下载:19/0  |  提交时间:2020/07/03

Triacylglycerols store metabolic energy in organisms and have industrial uses as foods and fuels. Excessive accumulation of triacylglycerols in humans causes obesity and is associated with metabolic diseases(1). Triacylglycerol synthesis is catalysed by acyl-CoA diacylglycerol acyltransferase (DGAT) enzymes(2-4), the structures and catalytic mechanisms of which remain unknown. Here we determined the structure of dimeric human DGAT1, a member of the membrane-bound O-acyltransferase (MBOAT) family, by cryo-electron microscopy at approximately 3.0 angstrom resolution. DGAT1 forms a homodimer through N-terminal segments and a hydrophobic interface, with putative active sites within the membrane region. A structure obtained with oleoyl-CoA substrate resolved at approximately 3.2 angstrom shows that the CoA moiety binds DGAT1 on the cytosolic side and the acyl group lies deep within a hydrophobic channel, positioning the acyl-CoA thioester bond near an invariant catalytic histidine residue. The reaction centre is located inside a large cavity, which opens laterally to the membrane bilayer, providing lipid access to the active site. A lipid-like density-possibly representing an acyl-acceptor molecule-is located within the reaction centre, orthogonal to acyl-CoA. Insights provided by the DGAT1 structures, together with mutagenesis and functional studies, provide the basis for a model of the catalysis of triacylglycerol synthesis by DGAT.


Cryo-electron microscopy structures and functional and mutagenesis studies provide insights into the catalysis of triacylglycerol synthesis by human acyl-CoA diacylglycerol acyltransferase at its intramembrane active site.


  
Recycling and metabolic flexibility dictate life in the lower oceanic crust 期刊论文
NATURE, 2020, 579 (7798) : 250-+
作者:  Zhou, Peng;  Yang, Xing-Lou;  Wang, Xian-Guang;  Hu, Ben;  Zhang, Lei;  Zhang, Wei;  Si, Hao-Rui;  Zhu, Yan;  Li, Bei;  Huang, Chao-Lin;  Chen, Hui-Dong;  Chen, Jing;  Luo, Yun;  Guo, Hua;  Jiang, Ren-Di;  Liu, Mei-Qin;  Chen, Ying;  Shen, Xu-Rui;  Wang, Xi;  Zheng, Xiao-Shuang;  Zhao, Kai;  Chen, Quan-Jiao;  Deng, Fei;  Liu, Lin-Lin;  Yan, Bing;  Zhan, Fa-Xian;  Wang, Yan-Yi;  Xiao, Geng-Fu;  Shi, Zheng-Li
收藏  |  浏览/下载:37/0  |  提交时间:2020/05/13

The lithified lower oceanic crust is one of Earth'  s last biological frontiers as it is difficult to access. It is challenging for microbiota that live in marine subsurface sediments or igneous basement to obtain sufficient carbon resources and energy to support growth(1-3) or to meet basal power requirements(4) during periods of resource scarcity. Here we show how limited and unpredictable sources of carbon and energy dictate survival strategies used by low-biomass microbial communities that live 10-750 m below the seafloor at Atlantis Bank, Indian Ocean, where Earth'  s lower crust is exposed at the seafloor. Assays of enzyme activities, lipid biomarkers, marker genes and microscopy indicate heterogeneously distributed and viable biomass with ultralow cell densities (fewer than 2,000 cells per cm(3)). Expression of genes involved in unexpected heterotrophic processes includes those with a role in the degradation of polyaromatic hydrocarbons, use of polyhydroxyalkanoates as carbon-storage molecules and recycling of amino acids to produce compounds that can participate in redox reactions and energy production. Our study provides insights into how microorganisms in the plutonic crust are able to survive within fractures or porous substrates by coupling sources of energy to organic and inorganic carbon resources that are probably delivered through the circulation of subseafloor fluids or seawater.


  
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.


  
Stakeholders strategies in poverty alleviation and clean energy access: A case study of China's PV poverty alleviation program 期刊论文
ENERGY POLICY, 2019, 135
作者:  Xu, Li;  Zhang, Qin;  Shi, Xunpeng
收藏  |  浏览/下载:8/0  |  提交时间:2020/02/17
Poverty alleviation  Access to clean energy  China  PV  Evolutionary game  GMCR  
A Historical Evaluation of the U15 Complex, Nevada National Security Site, Nye County, Nevada 科技报告
来源:US Department of Energy (DOE). 出版年: 2014
作者:  Drollinger, Harold;  Holz, Barbara A;  Bullard, Thomas F;  Goldenberg, Nancy G;  Ashbaugh, Laurence J;  Griffin, Wayne R
收藏  |  浏览/下载:8/0  |  提交时间:2019/04/05
This report presents a historical evaluation of the U15 Complex on the Nevada National Security Site (NNSS) in southern Nevada. The work was conducted by the Desert Research Institute at the request of the U.S. Department of Energy  National Nuclear Security Administration Nevada Field Office and the U.S. Department of Defense  Defense Threat Reduction Agency. Three underground nuclear tests and two underground nuclear fuel storage experiments were conducted at the complex. The nuclear tests were Hard Hat in 1962  Tiny Tot in 1965  and Pile Driver in 1966. The Hard Hat and Pile Driver nuclear tests involved different types of experiment sections in test drifts at various distances from the explosion in order to determine which sections could best survive in order to design underground command centers. The Tiny Tot nuclear test involved an underground cavity in which the nuclear test was executed. It also provided data in designing underground structures and facilities to withstand a nuclear attack. The underground nuclear fuel storage experiments were Heater Test 1 from 1977 to 1978 and Spent Fuel Test - Climax from 1978 to 1985. Heater Test 1 was used to design the later Spent Fuel Test - Climax experiment. The latter experiment was a model of a larger underground storage facility and primarily involved recording the conditions of the spent fuel and the surrounding granite medium. Fieldwork was performed intermittently in the summers of 2011 and 2013  totaling 17 days. Access to the underground tunnel complex is sealed and unavailable. Restricted to the surface  four buildings  four structures  and 92 features associated with nuclear testing and fuel storage experiment activities at the U15 Complex have been recorded. Most of these are along the west side of the complex and next to the primary access road and are characteristic of an industrial mining site  albeit one with scientific interests. The geomorphological fieldwork was conducted over three days in the summer of 2011. It was discovered that major modifications to the terrain have resulted from four principal activities. These are road construction and maintenance  mining activities related to development of the tunnel complex  site preparation for activities related to the tests and experiments  and construction of drill pads and retention ponds. Six large trenches for exploring across the Boundary geologic fault are also present. The U15 Complex  designated historic district 143 and site 26NY15177  is eligible to the National Register of Historic Places under Criteria A  C  and D of 36 CFR Part 60.4. As a historic district and archaeological site eligible to the National Register of Historic Places  the Desert Research Institute recommends that the area defined for the U15 Complex  historic district 143 and site 26NY15117  be left in place in its current condition. The U15 Complex should also be included in the NNSS cultural resources monitoring program and monitored for disturbances or alterations.  
Access to Energy in Developing Countries 科技报告
来源:Ecologic Institute (EU). 出版年: 2011
作者:  Eike Karola Velten
收藏  |  浏览/下载:2/0  |  提交时间:2019/04/05
access to energy  developing countries  rural regions  renewable energies  development policy  Developing countries  Sub-Saharan Africa  India