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ACS Central Science

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https://www.readbyqxmd.com/read/28058286/close-correlation-of-monoamine-oxidase-activity-with-progress-of-alzheimer-s-disease-in-mice-observed-by-in-vivo-two-photon-imaging
#1
Dokyoung Kim, Sung Hoon Baik, Seokjo Kang, Seo Won Cho, Juryang Bae, Moon-Yong Cha, Michael J Sailor, Inhee Mook-Jung, Kyo Han Ahn
Monoamine oxidases (MAOs) play an important role in Alzheimer's disease (AD) pathology. We report in vivo comonitoring of MAO activity and amyloid-β (Aβ) plaques dependent on the aging of live mice with AD, using a two-photon fluorescence probe. The probe under the catalytic action of MAO produces a dipolar fluorophore that senses Aβ plaques, a general AD biomarker, enabling us to comonitor the enzyme activity and the progress of AD indicated by Aβ plaques. The results show that the progress of AD has a close correlation with MAO activity, which can be categorized into three stages: slow initiation stage up to three months, an aggressive stage, and a saturation stage from nine months...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058285/large-hyperpolarizabilities-at-telecommunication-relevant-wavelengths-in-donor-acceptor-donor-nonlinear-optical-chromophores
#2
Animesh Nayak, Jaehong Park, Kurt De Mey, Xiangqian Hu, Timothy V Duncan, David N Beratan, Koen Clays, Michael J Therien
Octopolar D2-symmetric chromophores, based on the MPZnM supermolecular motif in which (porphinato)zinc(II) (PZn) and ruthenium(II) polypyridyl (M) structural units are connected via ethyne linkages, were synthesized. These structures take advantage of electron-rich meso-arylporphyrin or electron-poor meso-(perfluoroalkyl)porphyrin macrocycles, unsubstituted terpyridyl and 4'-pyrrolidinyl-2,2';6',2″-terpyridyl ligands, and modulation of metal(II) polypyridyl-to-(porphinato)zinc connectivity, to probe how electronic and geometric factors impact the measured hyperpolarizability...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058284/why-do-membranes-of-some-unhealthy-cells-adopt-a-cubic-architecture
#3
Qi Xiao, Zhichun Wang, Dewight Williams, Pawaret Leowanawat, Mihai Peterca, Samuel E Sherman, Shaodong Zhang, Daniel A Hammer, Paul A Heiney, Steven R King, David M Markovitz, Sabine André, Hans-Joachim Gabius, Michael L Klein, Virgil Percec
Nonlamellar lipid arrangements, including cubosomes, appear in unhealthy cells, e.g., when they are subject to stress, starvation, or viral infection. The bioactivity of cubosomes-nanoscale particles exhibiting bicontinuous cubic structures-versus more common vesicles is an unexplored area due to lack of suitable model systems. Here, glycodendrimercubosomes (GDCs)-sugar-presenting cubosomes assembled from Janus glycodendrimers by simple injection into buffer-are proposed as mimics of biological cubic membranes...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058283/insight-into-transmetalation-enables-cobalt-catalyzed-suzuki-miyaura-cross-coupling
#4
Jamie M Neely, Máté J Bezdek, Paul J Chirik
Among the fundamental transformations that comprise a catalytic cycle for cross coupling, transmetalation from the nucleophile to the metal catalyst is perhaps the least understood. Optimizing this elementary step has enabled the first example of a cobalt-catalyzed Suzuki-Miyaura cross coupling between aryl triflate electrophiles and heteroaryl boron nucleophiles. Key to this discovery was the preparation and characterization of a new class of tetrahedral, high-spin bis(phosphino)pyridine cobalt(I) alkoxide and aryloxide complexes, ((iPr)PNP)CoOR, and optimizing their reactivity with 2-benzofuranylBPin (Pin = pinacolate)...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058282/protein-degradation-by-in-cell-self-assembly-of-proteolysis-targeting-chimeras
#5
Honorine Lebraud, David J Wright, Christopher N Johnson, Tom D Heightman
Selective degradation of proteins by proteolysis targeting chimeras (PROTACs) offers a promising potential alternative to protein inhibition for therapeutic intervention. Current PROTAC molecules incorporate a ligand for the target protein, a linker, and an E3 ubiquitin ligase recruiting group, which bring together target protein and ubiquitinating machinery. Such hetero-bifunctional molecules require significant linker optimization and possess high molecular weight, which can limit cellular permeation, solubility, and other drug-like properties...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058281/unusual-base-pairing-interactions-in-monomer-template-complexes
#6
Wen Zhang, Chun Pong Tam, Jiawei Wang, Jack W Szostak
Many high-resolution crystal structures have contributed to our understanding of the reaction pathway for catalysis by DNA and RNA polymerases, but the structural basis of nonenzymatic template-directed RNA replication has not been studied in comparable detail. Here we present crystallographic studies of the binding of ribonucleotide monomers to RNA primer-template complexes, with the goal of improving our understanding of the mechanism of nonenzymatic RNA copying, and of catalysis by polymerases. To explore how activated ribonucleotides recognize and bind to RNA templates, we synthesized an unreactive phosphonate-linked pyrazole analogue of guanosine 5'-phosphoro-2-methylimidazolide (2-MeImpG), a highly activated nucleotide that has been used extensively to study nonenzymatic primer extension...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058280/anomalous-charge-transport-in-conjugated-polymers-reveals-underlying-mechanisms-of-trapping-and-percolation
#7
Sonya A Mollinger, Alberto Salleo, Andrew J Spakowitz
While transport in conjugated polymers has many similarities to that in crystalline inorganic materials, several key differences reveal the unique relationship between the morphology of polymer films and the charge mobility. We develop a model that directly incorporates the molecular properties of the polymer film and correctly predicts these unique transport features. At low degree of polymerization, the increase of the mobility with the polymer chain length reveals trapping at chain ends, and saturation of the mobility at high degree of polymerization results from conformational traps within the chains...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058279/molecular-caging-of-graphene-with-cyclohexane-transfer-and-electrical-transport
#8
Liubov A Belyaeva, Wangyang Fu, Hadi Arjmandi-Tash, Grégory F Schneider
Transfer of large, clean, crack- and fold-free graphene sheets is a critical challenge in the field of graphene-based electronic devices. Polymers, conventionally used for transferring two-dimensional materials, irreversibly adsorb yielding a range of unwanted chemical functions and contaminations on the surface. An oil-water interface represents an ideal support for graphene. Cyclohexane, the oil phase, protects graphene from mechanical deformation and minimizes vibrations of the water surface. Remarkably, cyclohexane solidifies at 7 °C forming a plastic crystal phase molecularly conforming graphene, preventing the use of polymers, and thus drastically limiting contamination...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058278/a-%C3%AE-mannanase-with-a-lysozyme-like-fold-and-a-novel-molecular-catalytic-mechanism
#9
Yi Jin, Marija Petricevic, Alan John, Lluís Raich, Huw Jenkins, Leticia Portela De Souza, Fiona Cuskin, Harry J Gilbert, Carme Rovira, Ethan D Goddard-Borger, Spencer J Williams, Gideon J Davies
The enzymatic cleavage of β-1,4-mannans is achieved by endo-β-1,4-mannanases, enzymes involved in germination of seeds and microbial hemicellulose degradation, and which have increasing industrial and consumer product applications. β-Mannanases occur in a range of families of the CAZy sequence-based glycoside hydrolase (GH) classification scheme including families 5, 26, and 113. In this work we reveal that β-mannanases of the newly described GH family 134 differ from other mannanase families in both their mechanism and tertiary structure...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058277/raman-spectroscopy-reveals-new-insights-into-the-zonal-organization-of-native-and-tissue-engineered-articular-cartilage
#10
Mads S Bergholt, Jean-Philippe St-Pierre, Giovanni S Offeddu, Paresh A Parmar, Michael B Albro, Jennifer L Puetzer, Michelle L Oyen, Molly M Stevens
Tissue architecture is intimately linked with its functions, and loss of tissue organization is often associated with pathologies. The intricate depth-dependent extracellular matrix (ECM) arrangement in articular cartilage is critical to its biomechanical functions. In this study, we developed a Raman spectroscopic imaging approach to gain new insight into the depth-dependent arrangement of native and tissue-engineered articular cartilage using bovine tissues and cells. Our results revealed previously unreported tissue complexity into at least six zones above the tidemark based on a principal component analysis and k-means clustering analysis of the distribution and orientation of the main ECM components...
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058276/unusual-hydrogen-bonding-patterns-and-the-role-of-the-backbone-in-nucleic-acid-information-transfer
#11
Steven A Benner
No abstract text is available yet for this article.
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058275/sticking-points
#12
Louisa Dalton
No abstract text is available yet for this article.
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058274/rebooting-the-molecular-computer
#13
Mark Peplow
No abstract text is available yet for this article.
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/28058273/a-season-of-giving-to-science
#14
EDITORIAL
Carolyn R Bertozzi, Miranda A Paley
No abstract text is available yet for this article.
December 28, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27981231/iron-catalysis-in-organic-synthesis-a-critical-assessment-of-what-it-takes-to-make-this-base-metal-a-multitasking-champion
#15
REVIEW
Alois Fürstner
The current status of homogeneous iron catalysis in organic chemistry is contemplated, as are the reasons why this particular research area only recently starts challenging the enduring dominance of the late and mostly noble metals over the field. Centered in the middle of the d-block and able to support formal oxidation states ranging from -II to +VI, iron catalysts hold the promise of being able to encompass organic synthesis at large. They are expected to serve reductive as well as oxidative regimes, can emulate "noble tasks", but are also able to adopt "early" transition metal character...
November 23, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27924316/discovery-of-febi2
#16
James P S Walsh, Samantha M Clarke, Yue Meng, Steven D Jacobsen, Danna E Freedman
Recent advances in high-pressure techniques offer chemists access to vast regions of uncharted synthetic phase space, expanding our experimental reach to pressures comparable to the core of the Earth. These newfound capabilities enable us to revisit simple binary systems in search of compounds that for decades have remained elusive. The most tantalizing of these targets are systems in which the two elements in question do not interact even as molten liquids-so-called immiscible systems. As a prominent example, immiscibility between iron and bismuth is so severe that no material containing Fe-Bi bonds is known to exist...
November 23, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27924315/control-of-selective-ion-transfer-across-liquid-liquid-interfaces-a-rectifying-heterojunction-based-on-immiscible-electrolytes
#17
Guillermo Iván Guerrero-García, Francisco J Solis, Kalyan Raidongia, Andrew Robert Koltonow, Jiaxing Huang, Mónica Olvera de la Cruz
The current rectification displayed by solid-state p-n semiconductor diodes relies on the abundance of electrons and holes near the interface between the p-n junction. In analogy to this electronic device, we propose here the construction of a purely ionic liquid-state electric rectifying heterojunction displaying an excess of monovalent cations and anions near the interface between two immiscible solvents with different dielectric properties. This system does not need any physical membrane or material barrier to show preferential ion transfer but relies on the ionic solvation energy between the two immiscible solvents...
November 23, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27924314/homogenous-electrocatalytic-oxygen-reduction-rates-correlate-with-reaction-overpotential-in-acidic-organic-solutions
#18
Michael L Pegis, Bradley A McKeown, Neeraj Kumar, Kai Lang, Derek J Wasylenko, X Peter Zhang, Simone Raugei, James M Mayer
Improved electrocatalysts for the oxygen reduction reaction (ORR) are critical for the advancement of fuel cell technologies. Herein, we report a series of 11 soluble iron porphyrin ORR electrocatalysts that possess turnover frequencies (TOFs) from 3 s(-1) to an unprecedented value of 2.2 × 10(6) s(-1). These TOFs correlate with the ORR overpotential, which can be modulated by changing the E1/2 of the catalyst using different ancillary ligands, by changing the solvent and solution acidity, and by changing the catalyst's protonation state...
November 23, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27924313/a-compartmentalized-out-of-equilibrium-enzymatic-reaction-network-for-sustained-autonomous-movement
#19
Marlies Nijemeisland, Loai K E A Abdelmohsen, Wilhelm T S Huck, Daniela A Wilson, Jan C M van Hest
Every living cell is a compartmentalized out-of-equilibrium system exquisitely able to convert chemical energy into function. In order to maintain homeostasis, the flux of metabolites is tightly controlled by regulatory enzymatic networks. A crucial prerequisite for the development of lifelike materials is the construction of synthetic systems with compartmentalized reaction networks that maintain out-of-equilibrium function. Here, we aim for autonomous movement as an example of the conversion of feedstock molecules into function...
November 23, 2016: ACS Central Science
https://www.readbyqxmd.com/read/27924312/protein-ligand-interaction-detection-with-a-novel-method-of-transient-induced-molecular-electronic-spectroscopy-times-experimental-and-theoretical-studies
#20
Tiantian Zhang, Tao Wei, Yuanyuan Han, Heng Ma, Mohammadreza Samieegohar, Ping-Wei Chen, Ian Lian, Yu-Hwa Lo
Protein-ligand interaction detection without disturbances (e.g., surface immobilization, fluorescent labeling, and crystallization) presents a key question in protein chemistry and drug discovery. The emergent technology of transient induced molecular electronic spectroscopy (TIMES), which incorporates a unique design of microfluidic platform and integrated sensing electrodes, is designed to operate in a label-free and immobilization-free manner to provide crucial information for protein-ligand interactions in relevant physiological conditions...
November 23, 2016: ACS Central Science
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