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https://www.readbyqxmd.com/read/27936444/amino-derivatives-of-platanic-acid-act-as-selective-and-potent-inhibitors-of-butyrylcholinesterase
#1
Lucie Heller, Michael Kahnt, Anne Loesche, Patricia Grabandt, Stefan Schwarz, Wolfgang Brandt, René Csuk
A set of thirtyfive 30-norlupan derivatives (2-36) was prepared from the natural triterpenoid platanic acid (PA), and the hydroxyl group at C-3, the carboxyl group at C-17 and the carbonyl group at C-20 were modified. These derivatives were tested for their inhibitory activity for the enzymes acetylcholinesterase (AChE, from electric eel) and butyrylcholinesterase (BChE, from equine serum) using Ellman's assay. Extra enzyme kinetic studies were performed. The most active compound was (3β, 20R)-3-acetyloxy-20-amino-30-norlupan-28-oate (32) showing a Ki value of 0...
November 30, 2016: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/27935959/crystal-structure-of-schistosoma-mansoni-adenosine-phosphorylase-5-methylthioadenosine-phosphorylase-and-its-importance-on-adenosine-salvage-pathway
#2
Juliana Roberta Torini, José Brandão-Neto, Ricardo DeMarco, Humberto D'Muniz Pereira
Schistosoma mansoni do not have de novo purine pathways and rely on purine salvage for their purine supply. It has been demonstrated that, unlike humans, the S. mansoni is able to produce adenine directly from adenosine, although the enzyme responsible for this activity was unknown. In the present work we show that S. mansoni 5´-deoxy-5´-methylthioadenosine phosphorylase (MTAP, E.C. 2.4.2.28) is capable of use adenosine as a substrate to the production of adenine. Through kinetics assays, we show that the Schistosoma mansoni MTAP (SmMTAP), unlike the mammalian MTAP, uses adenosine substrate with the same efficiency as MTA phosphorolysis, which suggests that this enzyme is part of the purine pathway salvage in S...
December 2016: PLoS Neglected Tropical Diseases
https://www.readbyqxmd.com/read/27935845/stability-and-aggregation-propensity-do-not-fully-account-for-the-association-of-various-germline-variable-domain-gene-segments-with-light-chain-amyloidosis
#3
Sergio A Garay Sánchez, Francisco Javier Rodríguez Álvarez, Guadalupe Zavala-Padilla, Luz María Mejia-Cristobal, Armando Cruz Rangel, Miguel Costas, D Alejandro Fernández Velasco, Jorge Melendez-Zajgla, Luis Del Pozo-Yauner
Variable domain (VL) gene segments exhibit variable tendencies to be associated with light chain amyloidosis (AL). While few of them are very frequent in AL and give rise to most of the amyloidogenic light chains compiled at the sequence databases, other are rarely found among the AL cases. To analyze to which extent these tendencies depend on folding stability and aggregation propensity of the germline VL protein, we characterized VL proteins encoded by four AL-associated germline gene segments and one not associated to AL...
November 17, 2016: Biological Chemistry
https://www.readbyqxmd.com/read/27935693/metastable-layered-cobalt-chalcogenides-from-topochemical-deintercalation
#4
Xiuquan Zhou, Brandon Wilfong, Hector Vivanco, Johnpierre Paglione, Craig M Brown, Efrain E Rodriguez
We present a general strategy to synthesize metastable layered materials via topochemical deintercalation of thermodynamically stable phases. Through kinetic control of the deintercalation reaction, we have prepared two hypothesized metastable compounds, CoSe and CoS, with the anti-PbO type structure from the starting compounds KCo2Se2 and KCo2S2, respectively. Thermal stability, crystal structure from X-ray and neutron diffraction, magnetic susceptibility, magnetization, and electrical resistivity are studied for these new layered chalcogenides; both CoSe and CoS are found to be weak itinerant ferromagnets with Curie temperatures close to 10 K...
December 9, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27935692/dynamic-and-electrostatic-effects-on-the-reaction-catalyzed-by-hiv-1-protease
#5
Agnieszka Krzemińska, Vicent Moliner, Katarzyna Świderek
HIV-1 Protease (HIV-1 PR) is one of the three enzymes essential for the replication process of HIV-1 virus, which explains why it has been the main target for design of drugs against acquired immunodeficiency syndrome (AIDS). This work is focused on exploring the proteolysis reaction catalyzed by HIV-1 PR, with special attention to the dynamic and electrostatic effects governing its catalytic power. Free energy surfaces for all possible mechanisms have been computed in terms of potentials of mean force (PMFs) within hybrid QM/MM potentials, with the QM subset of atoms described at semiempirical (AM1) and DFT (M06-2X) level...
December 9, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27935691/dna-mediated-morphological-control-of-pd-au-bimetallic-nanoparticles
#6
Nitya Sai Reddy Satyavolu, Li Huey Tan, Yi Lu
Recent reports have shown that different DNA sequences can mediate the control of shapes and surface properties of nanoparticles. However, all previous studies have involved only monometallic particles, most of which were gold nanoparticles. Controlling the shape of bimetallic nanoparticles is more challenging, and there is little research into the use of DNA-based ligands for their morphological control. We report the DNA-templated synthesis of Pd-Au bimetallic nanoparticles starting from palladium nanocube seeds...
December 9, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27935677/tryptophan-synthase-uses-an-atypical-mechanism-to-achieve-substrate-specificity
#7
Andrew R Buller, Paul van Roye, Javier Murciano-Calles, Frances H H Arnold
Tryptophan synthase (TrpS) catalyzes the final steps in the biosynthesis of L-tryptophan from L-serine (Ser) and indole-3-glycerol phosphate (IGP). We report that native TrpS can also catalyze a productive reaction with L-threonine (Thr), leading to (2S,3S)-β-methyltryptophan. Surprisingly, β-substitution occurs in vitro with a 3.4-fold higher catalytic efficiency for Ser over Thr using saturating indole, despite >82,000-fold preference for Ser in direct competition using IGP. Structural data identify a novel product binding site and kinetic experiments clarify the atypical mechanism of specificity: Thr binds efficiently but decreases the affinity for indole and disrupts the allosteric signaling that regulates the catalytic cycle...
December 9, 2016: Biochemistry
https://www.readbyqxmd.com/read/27935426/joint-stiffness-and-running-economy-during-imposed-forefoot-strike-before-and-after-a-long-run-in-rearfoot-strike-runners
#8
Daniel A Melcher, Max R Paquette, Brian K Schilling, Richard J Bloomer
Research has focused on the effects of acute strike pattern modifications on lower extremity joint stiffness and running economy (RE). Strike pattern modifications on running biomechanics have mostly been studied while runners complete short running bouts. This study examined the effects of an imposed forefoot strike (FFS) on RE and ankle and knee joint stiffness before and after a long run in habitual rearfoot strike (RFS) runners. Joint kinetics and RE were collected before and after a long run. Sagittal joint kinetics were computed from kinematic and ground reaction force data that were collected during over-ground running trials in 13 male runners...
December 9, 2016: Journal of Sports Sciences
https://www.readbyqxmd.com/read/27935314/a-versatile-method-to-determine-the-cellular-bioavailability-of-small-molecule-inhibitors
#9
Kevin B Teuscher, Min Zhang, Haitao Ji
The determination of the cellular bioavailability of small-molecule inhibitors is a critical step for interpreting cell-based data and guiding inhibitor optimization. Herein, a HPLC-MS based protocol was developed to determine inhibitor cellular bioavailability. This generalizable protocol allows determination of the accurate intracellular concentrations and characterization of various properties of inhibitors including the extra- and intracellular stability, the dose- and time-dependence of the intracellular concentrations, the cell permeability, and the nonspecific binding with the cell culture plates, the extracellular matrices, and the cell membrane...
December 9, 2016: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/27935302/accurate-dissociation-of-chemical-bonds-using-dft-in-dft-embedding-theory-with-external-orbital-orthogonality
#10
Patrick K Tamukong, Yuriy G Khait, Mark R Hoffmann
Our recent density functional theory (DFT)-in-DFT embedding protocol, which enforces inter-subsystem (or external orbital) orthogonality, is used for the first time to investigate covalent bond dissociation and is shown to do so accurately. Full potential energy curves for the dissociation of an H-O bond in H2O and the C-C bond in H3C-CH3 have been constructed using the new embedding method, as have the challenging ionic bonds in LiH and LiF, and were found to match the reference Kohn-Sham (KS)-DFT curves to at least one part in 10(6)...
December 9, 2016: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/27935299/strongly-coupled-feni-alloys-nife2o4-carbonitride-layers-assembled-microboxes-for-enhanced-oxygen-evolution-reaction
#11
Yangde Ma, Xiaoping Dai, Mengzhao Liu, Jiaxi Yong, Hongyan Qiao, Axiang Jin, Zhanzhao Li, Xingliang Huang, Hai Wang, Xin Zhang
Hydrogen produced from electrocatalytic water splitting is a promising route due to the sustainable powers derived from the solar and wind energy. However, the sluggish kinetics at the anode for water splitting makes the highly effective and inexpensive electrocatalysts desirable in oxygen evolution reaction (OER) by structure and composition modulations. Metal-organic frameworks (MOFs) have been intensively used as the templates/precursors to synthesize complex hollow structures for various energy-related applications...
December 9, 2016: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/27935291/a-comparison-between-the-photoactivation-kinetics-of-human-and-bovine-rhodopsins
#12
Chie Funatogawa, Istvan Szundi, David S Kliger
Rhodopsin is a G-protein-coupled receptor important for vertebrate vision under dim light conditions. Many studies of the activation mechanism of bovine rhodopsin have been conducted, but there have been relatively few investigations of the human protein. A recent study of the late photointermediates of bovine rhodopsin studies at 15 °C and pH 7.3, 8.0, and 8.7 revealed a rather complex activation mechanism involving two metarhodopsin I480 and metarhodopsin II intermediates. Human rhodopsin was studied under these same conditions using time-resolved optical absorption spectroscopy with measurements from 10 μs to 200 ms after photolysis...
December 9, 2016: Biochemistry
https://www.readbyqxmd.com/read/27935283/a-single-deoxynucleoside-kinase-variant-from-drosophila-melanogaster-synthesizes-monophosphates-of-nucleosides-that-are-components-of-an-expanded-genetic-system
#13
Mariko F Matsuura, Christian B Winiger, Ryan W Shaw, Myong-Jung Kim, Myong-Sang Kim, Ashley B Daugherty, Fei Chen, Patricia Moussatche, Jennifer D Moses, Stefan Lutz, Steven A Benner
Deoxynucleoside kinase from D. melanogaster (DmdNK) has broad specificity; although it catalyzes the phosphorylation of natural pyrimidine more efficiently than natural purine nucleosides, it accepts all four 2'-deoxynucleosides and many analogues, using ATP as a phosphate donor to give the corresponding deoxynucleoside monophosphates. Here, we show that replacing a single amino acid (glutamine 81 by glutamate) in DmdNK creates a variant that also catalyzes the phosphorylation of nucleosides that form part of an artificially expanded genetic information system (AEGIS)...
December 9, 2016: ACS Synthetic Biology
https://www.readbyqxmd.com/read/27935249/in-capillary-probing-of-quantum-dots-and-fluorescent-protein-self-assembly-and-displacement-using-f%C3%A3-rster-resonance-energy-transfer
#14
Jianhao Wang, Jie Fan, Jinchen Li, Li Liu, Jianpeng Wang, Pengju Jiang, Xiaoqian Liu, Lin Qiu
Herein, a Förster resonance energy transfer system was designed, which consisted of CdSe/ZnS quantum dots donor and mCherry fluorescent protein acceptor. The quantum dots and the mCherry proteins were conjugated to permit Förster resonance energy transfer. Capillary electrophoresis with fluorescence detection was used for the analyses for the described system. The quantum dots and mCherry were sequentially injected into the capillary, while the real-time fluorescence signal of donor and acceptor was simultaneously monitored by two channels with fixed wavelength detectors...
December 9, 2016: Journal of Separation Science
https://www.readbyqxmd.com/read/27935248/cisplatin-primary-complex-with-l-histidine-target-revealed-by-irmpd-spectroscopy
#15
Simonetta Fornarini, Davide Corinti, Alberto De Petris, Cecilia Coletti, Nazzareno Re, Barbara Chiavarino, Maria Elisa Crestoni
The primary complex obtained from cisplatin and L-histidine in water has been detected and isolated by electrospray ionization. The so-obtained cis-[PtCl(NH3)2(histidine)]+ complex has been thoroughly characterized by high resolution mass spectrometry (MS), tandem MS, IR multiple photon dissociation (IRMPD) spectroscopy and quantum chemical calculations. The structural features revealed by IRMPD spectroscopy indicate that platinum binds to the imidazole group, which presents tautomeric forms. Thus, depending on the position of the amino acid pendant on the imidazole ring, isomeric complexes are formed that are remarkably different in their ease to undergo fragmentation, when activated either by energetic collisions or by multiple IR photon absorption...
December 9, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/27935233/kinetic-analysis-of-de-novo-centriole-assembly-in-heat-shocked-mammalian-cells
#16
Keol Baek, Yeun Kyu Jang, Tae H Lee, JooHun Lee
Mammalian cells are capable of de novo centriole formation after the removal of existing centrioles. This suggests that de novo centriole assembly is repressed in normally duplicating cells to maintain a constant number of centrioles in the cells. However, neither the mechanism of de novo centriole assembly nor that of its hypothesized repression is understood due to the lack of an experimental system. We found that the heat shock (HS; 42°C, 2 h) of mouse embryonic fibroblasts caused the separation of centriole pairs, a transient increase in polo-like kinase (Plk) 4 expression, and the formation of a complex containing γ-tubulin, pericentrin, HS protein (Hsp) 90, and Plk4, in approximately half of the cells...
December 9, 2016: Cytoskeleton
https://www.readbyqxmd.com/read/27935210/mechanistic-insight-on-the-oxidation-of-organic-phenylselenides-by-h%C3%A2-o%C3%A2
#17
Giovanni Ribaudo, Massimo Bellanda, Ileana Menegazzo, Lando Peter Wolters, Marco Bortoli, Gerardo Ferrer-Sueta, Giuseppe Zagotto, Laura Orian
The oxidation of organic phenylselenides by H₂O₂ is investigated in model compounds, i.e. n-butyl phenyl selenide (PhSe(n-Bu)), bis(phenylselanyl)methane (PhSeMeSePh), diphenyl diselenide (PhSeSePh) and 1,2-bis(phenylselanyl)ethane (PhSeEtSePh). Through a combined experimental (¹H and ⁷⁷Se NMR) and computational approach, we characterize the direct oxidation of monoselenide to selenoxide, the stepwise double oxidation of PhSeMeSePh leading to different diastereomeric diselenoxides, the complete oxidation of the diphenyldiselenide leading to selenium-selenium bond cleavage and subsequent formation of the phenylseleninic product...
December 9, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27935056/chemiluminescence-of-cigarette-smoke-salient-features-of-the-phenomenon
#18
Galina F Fedorova, Valery A Menshov, Aleksei V Trofimov, Yury B Tsaplev, Rostislav F Vasil'ev, Olga I Yablonskaya
The study disclosed herein provides for the first time a detailed experimental support for the general mechanism of the cigarette-smoke-derived chemiluminescence, as an example par excellence of the excited-state generation in a chemically complex aerosol medium. The mechanism involves chemiexcitation in a unimolecular transformation of the smoke-borne free-radical species. However, the concentration of these radicals, [r(.) ], obeys a bimolecular (second-order) kinetics and depends on a particulate-phase content (total particulate matter, TPM) of the cigarette smoke...
December 9, 2016: Photochemistry and Photobiology
https://www.readbyqxmd.com/read/27934998/shear-driven-segregation-of-dry-granular-materials-with-different-friction-coefficients
#19
Katalin A Gillemot, Ellák Somfai, Tamás Börzsönyi
We report the first experimental demonstration of bulk segregation in a shear-driven dry granular mixture, where the particles only differ in their surface friction coefficients. We found that the smoother particles tend to sink to the bottom of the shear zone, while rough particles migrate to the top of the sample. This phenomenon is similar to the well known kinetic sieving in particle mixtures with size heterogeneity. In the present case the smooth particles have a higher probability to penetrate into voids created by the shearing than the rough ones...
December 9, 2016: Soft Matter
https://www.readbyqxmd.com/read/27934997/lead-pb-exposure-reduces-global-dna-methylation-level-by-non-competitive-inhibition-and-alteration-of-dnmt-expression
#20
Oscar F Sanchez, Jinyoung Lee, Nathaphon Yu King Hing, Seong-Eun Kim, Jennifer L Freeman, Chongli Yuan
Low-dose exposure to lead (Pb) is connected to developmental neurological alterations by inducing molecular changes, such as aberrant gene expression patterns. The attributing molecular mechanism, however, is not well-elucidated. In this study, we revealed epigenetic features and mechanisms that can alter gene expression patterns by identifying changes in DNA methyltransferase (DNMT) activity, expression pattern and DNA methylation level using moelcular studies and a zebrafish animal model. We characterized the effects of Pb on the activities of various DNMTs in vitro and determined the molecular role of Pb in modulating DNMT activity via kinetic experiments...
December 9, 2016: Metallomics: Integrated Biometal Science
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