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Denis Susorov, Nikita Zakharov, Ekaterina Shuvalova, Alexander Ivanov, Tatiana Egorova, Alexey Shuvalov, Ivan N Shatsky, Elena Alkalaeva
During protein synthesis, a ribosome moves along the mRNA template and, using aminoacyl-tRNAs, decodes the template nucleotide triplets to assemble a protein amino acid sequence. This movement is accompanied by shifting of mRNA-tRNA complexes within the ribosome in a process called translocation. In living cells, this process proceeds in a unidirectional manner, bringing the ribosome to the 3'-end of mRNA, and is catalyzed by the GTPase translation elongation factor 2 (EF-G in prokaryotes, eEF2 in eukaryotes)...
February 16, 2018: Journal of Biological Chemistry
Kuixin Cui, Bin Yan, Yijun Xie, Hui Qian, Xiaogang Wang, Qingxue Huang, Yuehui He, Shengming Jin, Hongbo Zeng
In this work, novel urchin-like Fe 3 O 4 @polydopamine (PDA)-Ag hollow microspheres have been prepared via a facile synthesis method by in situ reduction and growth of Ag nanoparticles on mussel-inspired PDA layers coated on Fe 3 O 4 hollow cores. The catalytic reduction efficiency and adsorption performance of the as-prepared urchin-like Fe 3 O 4 @polydopamine (PDA)-Ag hollow microspheres for model organic dyes (i.e., methylene blue and rhodamine B) under varying pH condition have been systematically investigated, which are demonstrated to be significantly enhanced as compared to that of spherical (relatively smooth) solid Fe 3 O 4 @PDA-Ag microspheres...
February 7, 2018: Journal of Hazardous Materials
Shukun Luo, Liang Tong
The cysteine protease separase opens the cohesin ring by cleaving its kleisin subunit and is a pivotal cell cycle factor for the transition from metaphase to anaphase. It is inhibited by forming a complex with the chaperone securin, and in vertebrates, also by the Cdk1-cyclin B1 complex. Separase is activated upon the destruction of securin or cyclin B1 by the proteasome, after ubiquitination by the anaphase-promoting complex/cyclosome (APC/C). Here we review recent structures of the active protease segment of Chaetomium thermophilum separase in complex with a substrate-mimic inhibitor and full-length Saccharomyces cerevisiae and Caenorhabditis elegans separase in complex with securin...
February 13, 2018: Current Opinion in Structural Biology
Markus Griesser, Ron Shah, Antonius T Van Kessel, Omkar Zilka, Evan A Haidasz, Derek A Pratt
Sterically-hindered nitroxides such as 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) have long been ascribed antioxidant activity that is thought to underlie their chemopreventive and anti-aging properties. However, the most commonly invoked reactions in this context - combination with an alkyl radical to give a redox inactive alkoxyamine or the catalysis of superoxide dismutation - are unlikely to be relevant under (most) physiological conditions. Herein we characterize the kinetics and mechanisms of the reactions of TEMPO, as well as an N-arylnitroxide and a N,N-diarylnitroxide, with alkylperoxyl radicals, the propagating species in lipid peroxidation...
February 16, 2018: Journal of the American Chemical Society
Julia Holz, Marta Ayerbe García, Wolfgang Frey, Felix Krupp, René Peters
In the last few decades, gold complexes have demonstrated huge potential for soft Lewis acid catalysis. Despite the intensive research on Au complexes and planar chiral metallacycles, enantiopure ferrocenylgold complexes have - surprisingly - not been reported until the studies presented in this article. Herein, we report the asymmetric synthesis of planar chiral ferrocenyl Au(i) complexes. These dinuclear species form helically chiral ten-membered (NCCCAu) 2 rings stabilized by aurophilic interactions. In supramolecular solid state structures, linear, zigzag or helical Au(i) wires with regular AuAu separations were observed...
February 16, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Hao Fang, Jinhu Yang, Ming Wen, Qingsheng Wu
Nanoalloys (NAs), which are distinctly different from bulk alloys or single metals, take on intrinsic features including tunable components and ratios, variable constructions, reconfigurable electronic structures, and optimizable performances, which endow NAs with fascinating prospects in the catalysis field. Here, the focus is on NA materials for chemical catalysis (except photocatalysis or electrocatalysis). In terms of composition, NA systems are divided into three groups, noble metal, base metal, and noble/base metal mixed NAs...
February 16, 2018: Advanced Materials
Andrés M Escorcia, Jeaphianne P M van Rijn, Gui-Juan Cheng, Patrick Schrepfer, Thomas B Brück, Walter Thiel
Molecular dynamics (MD) simulations have been performed to study the dynamic behavior of noncovalent enzyme carbocation complexes involved in the cyclization of geranylgeranyl diphosphate to taxadiene catalyzed by taxadiene synthase (TXS). Taxadiene and the observed four side products originate from the deprotonation of carbocation intermediates. The MD simulations of the TXS carbocation complexes provide insights into potential deprotonation mechanisms of such carbocations. The MD results do not support a previous hypothesis that carbocation tumbling is a key factor in the deprotonation of the carbocations by pyrophosphate...
February 15, 2018: Journal of Computational Chemistry
Soumitra Barman, Santu Das, Sreejith S S, Somnath Garai, Ramudu Pochamoni, Soumyajit Roy
A soft-oxometalate (SOM) based on Mo and V i.e. {MoV 9 } in their highest oxidation state reduces CO 2 to HCOOH selectively in water. Catalysis initiates without the use of any photosensitizer and solvent water acts as the sacrificial electron donor which gets oxidized to generate oxygen. Electrons and protons released in this process reduce CO 2 to HCOOH.
February 16, 2018: Chemical Communications: Chem Comm
Tyler G Saint-Denis, Ru-Yi Zhu, Gang Chen, Qing-Feng Wu, Jin-Quan Yu
Organic molecules are rich in carbon-hydrogen bonds; consequently, the transformation of C-H bonds to new functionalities (such as C-C, C-N, and C-O bonds) has garnered much attention by the synthetic chemistry community. The utility of C-H activation in organic synthesis, however, cannot be fully realized until chemists achieve stereocontrol in the modification of C-H bonds. This Review highlights recent efforts to enantioselectively functionalize C(sp 3 )-H bonds via transition metal catalysis, with an emphasis on key principles for both the development of chiral ligand scaffolds that can accelerate metalation of C(sp 3 )-H bonds and stereomodels for asymmetric metalation of prochiral C-H bonds by these catalysts...
February 16, 2018: Science
Kyung Hee Oh, Hyung Ju Park, Shin Wook Kang, Ji Chan Park, Ki Min Nam
Hollow nanomaterials have attracted great interest because of their many applications in catalysis, nanoreactors, drug delivery systems, for lubrication and in gas sensors. Here, carbon sphere templates were prepared from glucose under hydrothermal conditions to facilitate the synthesis of hollow Fe2O3 nanospheres. Thermal decomposition of an iron precursor in benzylalcohol with the carbon spheres resulted in the deposition of Fe3O4 nanoparticles on the carbon sphere templates. The nanoparticles on the carbon surface naturally agglomerate and form a dense oxide shell during the calcination step, which produces typical Fe2O3 hollow structures...
February 1, 2018: Journal of Nanoscience and Nanotechnology
S Ramakrishnan, E J Jelmy, R Senthilkumar, Murali Rangarajan, Nikhil K Kothurkar
Bilayer and few layer-graphene (Gr) with noble metal (Ag and Au) and TiO2 nanoparticles were synthesized using atmospheric pressure radio frequency chemical vapor deposition (APRF-CVD). The precursors for the formation of the respective nanoparticles were dissolved in ethanol and injected into the APRF-CVD containing a Cu foil catalyst at 1000 °C. The graphene obtained had a blistered morphology similar to bubble-wrap. The bubble-like protrusions on the graphene sheet were caused by large nanoparticle clusters (~220 nm) formed below the graphene sheets...
February 1, 2018: Journal of Nanoscience and Nanotechnology
Chun Liu, Sanghamitra Deb, Vinicius S Ferreira, Eric Xu, Tobias Baumgart
Phosphatidylinositides play important roles in cellular signaling and migration. Phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) is an important phosphatidylinositide because it acts as a secondary messenger to trigger cell movement and proliferation. A high level of PI(3,4,5)P3 at the plasma membrane is known to contribute to tumorigenesis. One key enzyme that regulates PI(3,4,5)P3 levels at the plasma membrane is phosphatase and tensin homologue deleted on chromosome 10 (PTEN), which dephosphorylates PI(3,4,5)P3 through hydrolysis to form phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)...
2018: PloS One
Tobias Morack, Jan B Metternich, Ryan Gilmour
An operationally simple protocol is disclosed to facilitate entry to benzo-3,4-coumarins directly from biaryl carboxylic acids without the need for substrate prefunctionalization. Complementary to classic lactonization strategies, this disconnection relies on the oxidation competence of photoactivated (-)-riboflavin (vitamin B 2 ) to generate the heterocyclic core via photoinduced single electron transfer. Collectively, the inexpensive nature of the catalyst, ease of execution, and absence of external metal additives are a convincing endorsement for the incorporation of simple vitamins in contemporary catalysis...
February 15, 2018: Organic Letters
Haoyue Xiang, Qing-Lan Zhao, Peng-Ju Xia, Jun-An Xiao, Zhi-Peng Ye, Xiong Xie, Huan Sheng, Xiao-Qing Chen, Hua Yang
A facile and diversified synthesis of functionalized CF 2 -containing benzoxepine derivatives via photoredox catalysis was achieved in this work. This novel protocol features broad substrate scope, mild reaction conditions, operational simplicity, easy scale-up, and versatile derivatization, which would facilitate its practical and broad applications in the construction of valuable and synthetically challenging heterocycles.
February 15, 2018: Organic Letters
Louis Jeanne-Julien, Eloi Astier, René Lai-Kuen, Grégory Genta-Jouve, Emmanuel Roulland
Reaction conditions allowing a stereoretentive cross-coupling of alkenyl sulfides with Grignard reagents using ligand-free Pd catalysis are discussed here. The presence of an adequately positioned OH function is a key feature that allows a Mg-promoted Lewis acid activation of the mercaptide leaving group. This easy to implement procedure actually relies on an in situ generation of stable Pd nanoparticles by simply mixing Pd 2 (dba) 3 , the Grignard reagent, and the vinyl sulfide cross-coupling partner in THF...
February 15, 2018: Organic Letters
Qing-Yuan Meng, Shun Wang, Gregory Huff, Burkhard König
The ligand-controlled Markovnikov and anti-Markovnikov hydrocarboxylation of styrenes with atmospheric pressure of CO 2 at room temperature using dual visible-light-nickel catalysis has been developed. In the presence of neocuproine as ligand, the Markovnikov product is obtained exclusively, while employing 1,4-bis(diphenyl¬phosphino)butane (dppb) as the ligand favors the formation of the anti-Markovnikov product. A range of functional groups and electron-poor, -neutral, as well as electron-rich styrene derivatives are tolerated by the reaction, providing the desired products in moderate to good yields...
February 15, 2018: Journal of the American Chemical Society
Marina González-Burgos, Jose A Pomposo
Ionic liquids (ILs) have shown advantages in organic synthesis and catalysis, energy storage and conversion, as well as a variety of pharmaceutical applications. Understanding the miscibility behavior of IL / monomer, IL / polymer and IL / polymer nanoparticle mixtures is critical for the use of ILs as green solvents in polymerization processes, as well as to rationalize recent observations concerning the superior solubility of some proteins in ILs when compared to standard solvents. In this work, the most relevant results obtained in terms of an extended three-component Flory-Huggins theory concerning the Extra Solvent Power (ESP) of ILs when compared to traditional non-ionic solvents for monomeric solutes (Case I), linear polymers (Case II), dry (i...
February 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Wei Qi, Pengqiang Yan, Dang Sheng Su
Sustainable and environmentally benign catalytic processes are vital for the future to supply the world population with clean energy and industrial products. The replacement of conventional metal or metal oxide catalysts with earth abundant and renewable nonmetallic materials has attracted considerable research interests in the field of catalysis and material science. The stable and efficient catalytic performance of nanocarbon materials was discovered at the end of last century, and these materials are considered as potential alternatives for conventional metal-based catalysts...
February 15, 2018: Accounts of Chemical Research
Yu Tang, Lingjuan Ma, Jian Dou, Christopher M Andolina, Yuting Li, Hongbin Ma, Stephen D House, Xiaoyan Zhang, Judith Yang, Franklin Feng Tao
In situ/operando studies of a heterogeneous catalyst are particularly valuable for achieving a fundamental understanding of catalytic mechanisms at a molecular level by establishing a correlation between the observed catalytic performance and the corresponding surface chemistry during catalysis. Herein, CO oxidation on cobalt oxides was studied via ambient pressure X-ray photoelectron spectroscopy (AP-XPS). During CO oxidation on CoO in the temperature range of 140-180 °C, the active surface phase of CoO progressively transforms to Co 3 O 4 ...
February 15, 2018: Physical Chemistry Chemical Physics: PCCP
Aniket Magarkar, Petteri Parkkila, Tapani Viitala, Tatu Lajunen, Edouard Mobarak, Giuseppe Licari, Oana Cramariuc, Eric Vauthey, Tomasz Róg, Alex Bunker
The enzyme catechol-O-methyltransferase (COMT) has water soluble (S-COMT) and membrane associated (MB-COMT), bitopic, isoforms. Of these MB-COMT is a drug target in relation to the treatment of Parkinson's disease. Using a combination of computational and experimental protocols, we have determined the substrate selection mechanism specific to MB-COMT. We show: (1) substrates with preferred affinity for MB-COMT over S-COMT orient in the membrane in a fashion conducive to catalysis from the membrane surface and (2) binding of COMT to its cofactor ADOMET induces conformational change that drives the catalytic surface of the protein to the membrane surface, where the substrates and Mg 2+ ions, required for catalysis, are found...
February 15, 2018: Chemical Communications: Chem Comm
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