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https://www.readbyqxmd.com/read/29629424/supramolecular-chemistry-of-anionic-dimers-trimers-tetramers-and-clusters
#1
Qing He, Peiyu Tu, Jonathan L Sessler
Two or more anions constrained in close proximity within a single pocket are found in a number of natural systems but a less common motif in artificial systems. This review summarizes work on anion receptors capable of stabilizing anionic dimers, trimers, tetramers and clusters in a well-defined fashion. These systems may provide insights into the fundamental chemistry of anion-anion interactions and provide a guide for understanding in greater detail a number of biological and environmental processes, as well as key tenants of relevance to supramolecular chemistry, extraction, transport, crystal engineering, and the like...
January 11, 2018: Chem
https://www.readbyqxmd.com/read/29094109/a-water-bridged-cysteine-cysteine-redox-regulation-mechanism-in-bacterial-protein-tyrosine-phosphatases
#2
Jean B Bertoldo, Tiago Rodrigues, Lavinia Dunsmore, Francesco A Aprile, Marta C Marques, Leonardo A Rosado, Omar Boutureira, Thomas B Steinbrecher, Woody Sherman, Francisco Corzana, Hernán Terenzi, Gonçalo J L Bernardes
The emergence of multidrug-resistant Mycobacterium tuberculosis ( Mtb ) strains highlights the need to develop more efficacious and potent drugs. However, this goal is dependent on a comprehensive understanding of Mtb virulence protein effectors at the molecular level. Here, we used a post-expression cysteine (Cys)-to-dehydrolanine (Dha) chemical editing strategy to identify a water-mediated motif that modulates accessibility of the protein tyrosine phosphatase A (PtpA) catalytic pocket. Importantly, this water-mediated Cys-Cys non-covalent motif is also present in the phosphatase SptpA from Staphylococcus aureus , which suggests a potentially preserved structural feature among bacterial tyrosine phosphatases...
October 12, 2017: Chem
https://www.readbyqxmd.com/read/28770257/nanoparticle-based-receptors-mimic-protein-ligand-recognition
#3
Laura Riccardi, Luca Gabrielli, Xiaohuan Sun, Federico De Biasi, Federico Rastrelli, Fabrizio Mancin, Marco De Vivo
The self-assembly of a monolayer of ligands on the surface of noble-metal nanoparticles dictates the fundamental nanoparticle's behavior and its functionality. In this combined computational-experimental study, we analyze the structure, organization, and dynamics of functionalized coating thiols in monolayer-protected gold nanoparticles (AuNPs). We explain how functionalized coating thiols self-organize through a delicate and somehow counterintuitive balance of interactions within the monolayer itself and with the solvent...
July 13, 2017: Chem
https://www.readbyqxmd.com/read/28966989/bright-long-lived-luminescence-of-silicon-nanocrystals-sensitized-by-two-photon-absorbing-antenna
#4
Luca Ravotto, Qi Chen, Yuguo Ma, Sergei A Vinogradov, Mirko Locritani, Giacomo Bergamini, Fabrizia Negri, Yixuan Yu, Brian A Korgel, Paola Ceroni
Silicon nanocrystals of the average diameter of 5 nm, functionalized with 4,7-di(2-thienyl)-2,1,3-benzothiadiazole chromophores ( TBT ) and dodecyl chains, exhibit near-infrared emission upon one-photon (1P) excitation at 515 nm and two-photon (2P) excitation at 960 nm. By using TBT chromophores as an antenna we were able to enhance both 1P and 2P absorption cross-sections of the silicon nanocrystals to more efficiently excite their long-lived luminescence. These results chart a path to two-photon-excitable imaging probes with long-lived oxygen-independent luminescence - a rare combination of properties that should allow for a substantial increase in imaging contrast...
April 13, 2017: Chem
https://www.readbyqxmd.com/read/28516168/selective-surface-pegylation-of-uio-66-nanoparticles-for-enhanced-stability-cell-uptake-and-ph-responsive-drug-delivery
#5
Isabel Abánades Lázaro, Salame Haddad, Sabrina Sacca, Claudia Orellana-Tavra, David Fairen-Jimenez, Ross S Forgan
The high storage capacities and excellent biocompatibilities of metal-organic frameworks (MOFs) have made them emerging candidates as drug-delivery vectors. Incorporation of surface functionality is a route to enhanced properties, and here we report on a surface-modification procedure-click modulation-that controls their size and surface chemistry. The zirconium terephthalate MOF UiO-66 is (1) synthesized as ∼200 nm nanoparticles coated with functionalized modulators, (2) loaded with cargo, and (3) covalently surface modified with poly(ethylene glycol) (PEG) chains through mild bioconjugate reactions...
April 13, 2017: Chem
https://www.readbyqxmd.com/read/28948238/calling-all-hosts-bacterial-communication-in-situ
#6
Jessica L Cleary, Alanna R Condren, Katherine E Zink, Laura M Sanchez
Bacteria are cosmopolitan organisms that in recent years have demonstrated many roles in maintaining host equilibrium. In this review, we discuss three roles bacteria can occupy in a host: pathogenic, symbiotic, and transient, with a specific focus on how bacterial small molecules contribute to homeostasis or dysbiosis. First, we will dissect how small molecules produced by pathogenic bacteria can be used as a source for communication during colonization and as protection against host immune responses. The ability to achieve a higher level of organization through small molecule communication gives pathogenic bacteria an opportunity for increased virulence and fitness...
March 9, 2017: Chem
https://www.readbyqxmd.com/read/28367516/hierarchical-self-assembly-of-halogen-bonded-block-copolymer-complexes-into-upright-cylindrical-domains
#7
Roberto Milani, Nikolay Houbenov, Francisco Fernandez-Palacio, Gabriella Cavallo, Alessandro Luzio, Johannes Haataja, Gabriele Giancane, Marco Saccone, Arri Priimagi, Pierangelo Metrangolo, Olli Ikkala
Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers...
March 9, 2017: Chem
https://www.readbyqxmd.com/read/28149959/synthesis-of-hetero-bifunctional-end-capped-oligo-edot-derivatives
#8
Christopher D Spicer, Marsilea A Booth, Damia Mawad, Astrid Armgarth, Christian B Nielsen, Molly M Stevens
Conjugated oligomers of 3,4-ethylenedioxythiophene (EDOT) are attractive materials for tissue engineering applications and as model systems for studying the properties of the widely used polymer poly(3,4-ethylenedioxythiophene). We report here the facile synthesis of a series of keto-acid end-capped oligo-EDOT derivatives (n = 2-7) through a combination of a glyoxylation end-capping strategy and iterative direct arylation chain extension. Importantly, these structures not only represent the longest oligo-EDOTs reported but are also bench stable, in contrast to previous reports on such oligomers...
January 12, 2017: Chem
https://www.readbyqxmd.com/read/27790643/computational-screening-of-all-stoichiometric-inorganic-materials
#9
Daniel W Davies, Keith T Butler, Adam J Jackson, Andrew Morris, Jarvist M Frost, Jonathan M Skelton, Aron Walsh
Forming a four-component compound from the first 103 elements of the periodic table results in more than 10(12) combinations. Such a materials space is intractable to high-throughput experiment or first-principle computation. We introduce a framework to address this problem and quantify how many materials can exist. We apply principles of valency and electronegativity to filter chemically implausible compositions, which reduces the inorganic quaternary space to 10(10) combinations. We demonstrate that estimates of band gaps and absolute electron energies can be made simply on the basis of the chemical composition and apply this to the search for new semiconducting materials to support the photoelectrochemical splitting of water...
October 13, 2016: Chem
https://www.readbyqxmd.com/read/28462396/photochemical-perfluoroalkylation-with-pyridine-n-oxides-mechanistic-insights-and-performance-on-a-kilogram-scale
#10
Joel W Beatty, James J Douglas, Richard Miller, Rory C McAtee, Kevin P Cole, Corey R J Stephenson
The direct trifluoromethylation of (hetero)arenes is a process of high importance to the pharmaceutical industry. Many reagents exist for this purpose and have found widespread use in discovery efforts; however, the step-intensive preparation of these reagents and their corresponding cost have resulted in minimal use of these methods in large-scale applications. For the ready transition of direct trifluoromethylation methodologies to large-scale application, the further development of processes utilizing inexpensive CF3 sources available on a metric ton scale is highly desirable...
September 8, 2016: Chem
https://www.readbyqxmd.com/read/28393126/enzyme-instructed-self-assembly-for-spatiotemporal-profiling-of-the-activities-of-alkaline-phosphatases-on-live-cells
#11
Jie Zhou, Xuewen Du, Cristina Berciu, Hongjian He, Junfeng Shi, Daniela Nicastro, Bing Xu
Alkaline phosphatase (ALP), an ectoenzyme, plays important roles in biology. But there is no activity probes for imaging ALPs in live cell environment due to the diffusion and cytotoxicity of current probes. Here we report the profiling of the activities of ALPs on live cells by enzyme-instructed self-assembly (EISA) of a D-peptidic derivative that forms fluorescent, non-diffusive nanofibrils. Our study reveals the significantly higher activities of ALP on cancer cells than on stromal cells in their co-culture and shows an inherent and dynamic difference in ALP activities between drug sensitive and resistant cancer cells or between cancer cells with and without hormonal stimulation...
August 11, 2016: Chem
https://www.readbyqxmd.com/read/27891534/graphene-oxide-nanosheets-stimulate-ruffling-and-shedding-of-mammalian-cell-plasma-membranes
#12
Chao Sun, Devin L Wakefield, Yimo Han, David A Muller, David A Holowka, Barbara A Baird, William R Dichtel
Graphene oxide (GO) has attracted intense interest for use in living systems and environmental applications. GO's compatibility with mammalian cells is sometimes inferred from its low cytotoxicity, but such conclusions ignore non-lethal effects that will influence GO's utility. Here we demonstrate, with rat basophilic leukemia (RBL) cells, profound plasma membrane (PM) ruffling and shedding induced by GO using confocal and live cell fluorescence microscopy, as well as scanning electron microscopy. These membrane structures contain immunoglobulin E receptors, are resistant to detergents, and lack detectable fluorescence labeling of F-actin and fibronectin...
August 11, 2016: Chem
https://www.readbyqxmd.com/read/28255579/immunomodulatory-effects-of-coated-gold-nanoparticles-in-lps-stimulated-in-vitro-and-in-vivo-murine-model-systems
#13
Daniel F Moyano, Yuanchang Liu, Furkan Ayaz, Singyuk Hou, Premsak Puangploy, Bradley Duncan, Barbara A Osborne, Vincent M Rotello
The ability of nanoparticle surface functionalities to regulate immune responses during an immunological challenge (i. e. inflammation) would open new doors for their use in non-prophylactic therapeutics. We report here the use of functionalized 2 nm core gold nanoparticles to control the immunological responses of in vitro and in vivo systems presented with an inflammatory challenge. The results showed that NPs bearing a hydrophobic zwitterionic functionality boost inflammatory outcomes while hydrophilic zwitterionic NPs generate minimal immunological responses...
2016: Chem
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