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ACS Central Science

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https://www.readbyqxmd.com/read/28776023/nitroxide-based-macromolecular-contrast-agents-with-unprecedented-transverse-relaxivity-and-stability-for-magnetic-resonance-imaging-of-tumors
#1
Hung V-T Nguyen, Qixian Chen, Joseph T Paletta, Peter Harvey, Yivan Jiang, Hui Zhang, Michael D Boska, M Francesca Ottaviani, Alan Jasanoff, Andrzej Rajca, Jeremiah A Johnson
Metal-free magnetic resonance imaging (MRI) agents could overcome the established toxicity associated with metal-based agents in some patient populations and enable new modes of functional MRI in vivo. Herein, we report nitroxide-functionalized brush-arm star polymer organic radical contrast agents (BASP-ORCAs) that overcome the low contrast and poor in vivo stability associated with nitroxide-based MRI contrast agents. As a consequence of their unique nanoarchitectures, BASP-ORCAs possess per-nitroxide transverse relaxivities up to ∼44-fold greater than common nitroxides, exceptional stability in highly reducing environments, and low toxicity...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776022/smart-nanocatalysts-with-streamline-shapes
#2
Guowu Zhan, Hua Chun Zeng
Particulate catalysts with streamline shapes have important impacts on fluid-related reactions, and they need to be properly characterized. However, utilization of streamline-shaped catalysts for heterogeneous catalysis has remained an unexplored area due to the lack of easy-to-use techniques to produce such shaped catalysts, especially at the small length scale of the submicron to micron regime. Herein, we report our recent development of a class of prototype nanocatalysts with streamline shapes. In this research, the kinetic control is adapted to obtain streamline-shaped supports, followed by functionalizing such supports with catalytically active metal nanoclusters (e...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776021/1-6-cyclophellitol-cyclosulfates-a-new-class-of-irreversible-glycosidase-inhibitor
#3
Marta Artola, Liang Wu, Maria J Ferraz, Chi-Lin Kuo, Lluís Raich, Imogen Z Breen, Wendy A Offen, Jeroen D C Codée, Gijsbert A van der Marel, Carme Rovira, Johannes M F G Aerts, Gideon J Davies, Herman S Overkleeft
The essential biological roles played by glycosidases, coupled to the diverse therapeutic benefits of pharmacologically targeting these enzymes, provide considerable motivation for the development of new inhibitor classes. Cyclophellitol epoxides and aziridines are recently established covalent glycosidase inactivators. Inspired by the application of cyclic sulfates as electrophilic equivalents of epoxides in organic synthesis, we sought to test whether cyclophellitol cyclosulfates would similarly act as irreversible glycosidase inhibitors...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776020/electrolytic-co2-reduction-in-tandem-with-oxidative-organic-chemistry
#4
Tengfei Li, Yang Cao, Jingfu He, Curtis P Berlinguette
Electrochemical reduction of CO2 into carbon-based products using excess clean electricity is a compelling method for producing sustainable fuels while lowering CO2 emissions. Previous electrolytic CO2 reduction studies all involve dioxygen production at the anode, yet this anodic reaction requires a large overpotential and yields a product bearing no economic value. We report here that the cathodic reduction of CO2 to CO can occur in tandem with the anodic oxidation of organic substrates that bear higher economic value than dioxygen...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776019/highly-efficient-thermally-activated-delayed-fluorescence-from-an-excited-state-intramolecular-proton-transfer-system
#5
Masashi Mamada, Ko Inada, Takeshi Komino, William J Potscavage, Hajime Nakanotani, Chihaya Adachi
Thermally activated delayed fluorescence (TADF) materials have shown great potential for highly efficient organic light-emitting diodes (OLEDs). While the current molecular design of TADF materials primarily focuses on combining donor and acceptor units, we present a novel system based on the use of excited-state intramolecular proton transfer (ESIPT) to achieve efficient TADF without relying on the well-established donor-acceptor scheme. In an appropriately designed acridone-based compound with intramolecular hydrogen bonding, ESIPT leads to separation of the highest occupied and lowest unoccupied molecular orbitals, resulting in TADF emission with a photoluminescence quantum yield of nearly 60%...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776018/metathesis-activity-encoded-in-the-metallacyclobutane-carbon-13-nmr-chemical-shift-tensors
#6
Christopher P Gordon, Keishi Yamamoto, Wei-Chih Liao, Florian Allouche, Richard A Andersen, Christophe Copéret, Christophe Raynaud, Odile Eisenstein
Metallacyclobutanes are an important class of organometallic intermediates, due to their role in olefin metathesis. They can have either planar or puckered rings associated with characteristic chemical and physical properties. Metathesis active metallacyclobutanes have short M-Cα/α' and M···Cβ distances, long Cα/α'-Cβ bond length, and isotropic (13)C chemical shifts for both early d(0) and late d(4) transition metal compounds for the α- and β-carbons appearing at ca. 100 and 0 ppm, respectively. Metallacyclobutanes that do not show metathesis activity have (13)C chemical shifts of the α- and β-carbons at typically 40 and 30 ppm, respectively, for d(0) systems, with upfield shifts to ca...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776017/tunable-multiscale-nanoparticle-ordering-by-polymer-crystallization
#7
Dan Zhao, Vianney Gimenez-Pinto, Andrew M Jimenez, Longxi Zhao, Jacques Jestin, Sanat K Kumar, Brooke Kuei, Enrique D Gomez, Aditya Shanker Prasad, Linda S Schadler, Mohammad M Khani, Brian C Benicewicz
While ∼75% of commercially utilized polymers are semicrystalline, the generally low mechanical modulus of these materials, especially for those possessing a glass transition temperature below room temperature, restricts their use for structural applications. Our focus in this paper is to address this deficiency through the controlled, multiscale assembly of nanoparticles (NPs), in particular by leveraging the kinetics of polymer crystallization. This process yields a multiscale NP structure that is templated by the lamellar semicrystalline polymer morphology and spans NPs engulfed by the growing crystals, NPs ordered into layers in the interlamellar zone [spacing of [Formula: see text] (10-100 nm)], and NPs assembled into fractal objects at the interfibrillar scale, [Formula: see text] (1-10 μm)...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776016/mechanistic-investigation-of-the-specific-anticancer-property-of-artemisinin-and-its-combination-with-aminolevulinic-acid-for-enhanced-anticolorectal-cancer-activity
#8
Jigang Wang, Jianbin Zhang, Yin Shi, Chengchao Xu, Chongjing Zhang, Yin Kwan Wong, Yew Mun Lee, Sanjeev Krishna, Yingke He, Teck Kwang Lim, Weiying Sim, Zi-Chun Hua, Han-Ming Shen, Qingsong Lin
The antimalarial artemisinin (ART) possesses anticancer activity, but its underlying mechanism remains largely unclear. Using a chemical proteomics approach with artemisinin-based activity probes, we identified over 300 specific ART targets. This reveals an anticancer mechanism whereby ART promiscuously targets multiple critical biological pathways and leads to cancer cell death. The specific cytotoxicity of ART against colorectal cancer (CRC) cells rather than normal colon epithelial cells is due to the elevated capacity of heme synthesis in the cancer cells...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776015/computationally-guided-synthetic-control-over-pore-size-in-isostructural-porous-organic-cages
#9
Anna G Slater, Paul S Reiss, Angeles Pulido, Marc A Little, Daniel L Holden, Linjiang Chen, Samantha Y Chong, Ben M Alston, Rob Clowes, Maciej Haranczyk, Michael E Briggs, Tom Hasell, Graeme M Day, Andrew I Cooper
The physical properties of 3-D porous solids are defined by their molecular geometry. Hence, precise control of pore size, pore shape, and pore connectivity are needed to tailor them for specific applications. However, for porous molecular crystals, the modification of pore size by adding pore-blocking groups can also affect crystal packing in an unpredictable way. This precludes strategies adopted for isoreticular metal-organic frameworks, where addition of a small group, such as a methyl group, does not affect the basic framework topology...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776014/new-tricks-of-the-trade-for-crystal-structure-refinement
#10
Jinjin Li, Yuriy A Abramov, Michael F Doherty
Accurate crystal structures and their experimental uncertainties, determined by X-ray diffraction/neutron diffraction techniques, are vital for crystal engineering studies, such as polymorph stability and crystal morphology calculations. Because of differences in crystal growth and data measurement conditions, crystallographic databases often contain multiple entries of varying quality of the same compound. The choice of the most reliable and best quality crystal structure from many very similar structures remains an unresolved problem, especially for nonexperts...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776013/cloud-activation-potentials-for-atmospheric-%C3%AE-pinene-and-%C3%AE-caryophyllene-ozonolysis-products
#11
Ariana Gray Bé, Mary Alice Upshur, Pengfei Liu, Scot T Martin, Franz M Geiger, Regan J Thomson
The formation of atmospheric cloud droplets due to secondary organic aerosol (SOA) particles is important for quantifying the Earth's radiative balance under future, possibly warmer, climates, yet is only poorly understood. While cloud activation may be parametrized using the surface tension depression that coincides with surfactant partitioning to the gas-droplet interface, the extent to which cloud activation is influenced by both the chemical structure and reactivity of the individual molecules comprising this surfactant pool is largely unknown...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776012/dna-s-chiral-spine-of-hydration
#12
M Luke McDermott, Heather Vanselous, Steven A Corcelli, Poul B Petersen
The iconic helical structure of DNA is stabilized by the solvation environment, where a change in the hydration state can lead to dramatic changes to the DNA structure. X-ray diffraction experiments at cryogenic temperatures have shown crystallographic water molecules in the minor groove of DNA, which has led to the notion of a spine of hydration of DNA. Here, chiral nonlinear vibrational spectroscopy of two DNA sequences shows that not only do such structural water molecules exist in solution at ambient conditions but that they form a chiral superstructure: a chiral spine of hydration...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776011/making-the-message-clear-concepts-for-mrna-imaging
#13
REVIEW
Kristina Rau, Andrea Rentmeister
The transcriptome of each individual cell contains numerous RNA species, each of which can be controlled by multiple mechanisms during their lifetime. The standard transcriptome analysis focuses on the expression levels of the genes of interest. To gain additional insights into spatiotemporal RNA distribution and the underlying trafficking processes, RNA labeling and imaging are necessary-ideally in living cells. This perspective will summarize state-of-the-art RNA imaging methods including their strengths and weaknesses...
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776010/transition-metal-catalysis-of-nucleophilic-substitution-reactions-a-radical-alternative-to-sn1-and-sn2-processes
#14
REVIEW
Gregory C Fu
Classical methods for achieving nucleophilic substitutions of alkyl electrophiles (SN1 and SN2) have limited scope and are not generally amenable to enantioselective variants that employ readily available racemic electrophiles. Radical-based pathways catalyzed by chiral transition-metal complexes provide an attractive approach to addressing these limitations.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776009/a-layered-look-for-spherical-nanoparticles-in-semicrystalline-polymers
#15
Richard A Register
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776008/electrosynthesis-a-new-frontier-in-aerobic-oxidation
#16
Carlo Sambiagio, Hans Sterckx, Bert U W Maes
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776007/the-h2o-helix-the-chiral-water-superstructure-surrounding-dna
#17
Ethan A Perets, Elsa C Y Yan
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776006/monitoring-methane
#18
Prachi Patel
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776005/a-conversation-with-tom%C3%A3-s-palacios
#19
Katherine Bourzac
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
https://www.readbyqxmd.com/read/28776004/altmetrics-broadening-impact-or-amplifying-voices
#20
EDITORIAL
C R Sugimoto, V Larivière
No abstract text is available yet for this article.
July 26, 2017: ACS Central Science
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