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https://www.readbyqxmd.com/read/29169026/structures-and-mechanisms-in-clay-nanopore-trapping-of-structurally-different-fluoroquinolone-antimicrobials
#1
Fanny E K Okaikue-Woodi, Sabrina E Kelch, Michael P Schmidt, Carmen Enid Martinez, Randall E Youngman, Ludmilla Aristilde
Smectite clay nanoparticles are implicated in the retention of antimicrobials within soils and sediments; these clays are also inspected as drug carriers in physiological systems. Cation exchange is considered the primary adsorption mechanism of antimicrobials within smectite nanopores. However, a dual role of acid-base chemistry and adsorptive structures is speculated by recent studies. Using the prototypical smectite clay montmorillonite, we employed a combination of X-ray diffraction (XRD), nuclear magnetic resonance, attenuated total reflectance-Fourier transform infrared spectroscopy, and molecular dynamics simulations to investigate the interlayer nanopore trapping of two structurally-different fluoroquinolone (FQ) antimicrobials with similar acid-base chemistry: ciprofloxacin (a first-generation FQ) and moxifloxacin (a third-generation FQ)...
November 8, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29168252/global-substrate-specificity-profiling-of-post-translational-modifying-enzymes
#2
REVIEW
Sam L Ivry, Nicole O Meyer, Michael B Winter, Markus F Bohn, Giselle M Knudsen, Anthony J O'Donoghue, Charles S Craik
Enzymes that modify the proteome, referred to as post-translational modifying (PTM) enzymes, are central regulators of cellular signaling. Determining the substrate specificity of PTM enzymes is a critical step in unraveling their biological functions both in normal physiological processes and in disease states. Advances in peptide chemistry over the last century have enabled the rapid generation of peptide libraries for querying substrate recognition by PTM enzymes. In this review, we highlight various peptide-based approaches for analysis of PTM enzyme substrate specificity...
November 23, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/29167789/radical-sam-enzymes-in-the-biosynthesis-of-ribosomally-synthesized-and-post-translationally-modified-peptides-ripps
#3
REVIEW
Alhosna Benjdia, Clémence Balty, Olivier Berteau
Ribosomally-synthesized and post-translationally modified peptides (RiPPs) are a large and diverse family of natural products. They possess interesting biological properties such as antibiotic or anticancer activities, making them attractive for therapeutic applications. In contrast to polyketides and non-ribosomal peptides, RiPPs derive from ribosomal peptides and are post-translationally modified by diverse enzyme families. Among them, the emerging superfamily of radical SAM enzymes has been shown to play a major role...
2017: Frontiers in Chemistry
https://www.readbyqxmd.com/read/29166014/probing-the-surface-of-platinum-during-the-hydrogen-evolution-reaction-in-alkaline-electrolyte
#4
Kelsey A Stoerzinger, Marco Favaro, Philip N Ross, Junko Yano, Zhi Liu, Zahid Hussain, Ethan J Crumlin
Understanding the surface chemistry of electrocatalysts in operando can bring insight into the reaction mechanism, and ultimately the design of more efficient materials for sustainable energy storage and conversion. Recent progress in synchrotron based X-ray spectroscopies for in operando characterization allows us to probe the solid/liquid interface directly while applying an external potential, applied here to the model system of Pt in alkaline electrolyte for the hydrogen evolution reaction (HER). We employ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify the oxidation and reduction of Pt-oxides and hydroxides on the surface as a function of applied potential, and further assess the potential for hydrogen adsorption and absorption (hydride formation) during and after the HER...
November 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29165467/enantiomer-surface-chemistry-conglomerate-versus-racemate-formation-on-surfaces
#5
REVIEW
Soham Dutta, Andrew J Gellman
Research on surface chirality is motivated by the need to develop functional chiral surfaces for enantiospecific applications. While molecular chirality in 3D has been the subject of study for almost two centuries, many aspects of 2D chiral surface chemistry have yet to be addressed. In 3D, racemic mixtures of chiral molecules tend to aggregate into racemate (molecularly heterochiral) crystals much more frequently than conglomerate (molecularly homochiral) crystals. Whether chiral adsorbates on surfaces preferentially aggregate into heterochiral rather than homochiral domains (2D crystals or clusters) is not known...
November 22, 2017: Chemical Society Reviews
https://www.readbyqxmd.com/read/29165062/recent-progress-of-crosslinking-strategies-for-polymeric-micelles-with-enhanced-drug-delivery-in-cancer-therapy
#6
Wei Fan, Luye Zhang, Yiwen Li, Haoxing Wu
The drug delivery by versatile types of self-assembled micelles for tumor treatment, which improved the diagnostic and therapeutic effectiveness, is advocated. However, despite the numerous advantages, applications of most micelle system have been retarded by low in vivo bio-stability which led to premature drug release and nonspecific tissue accumulation. To date, a range of chemistries has been introduced in intermolecular non-covalent/covalent crosslinking strategies for these dynamic nanostructures to produce robust functional nanoparticles with enhanced circulation stability and lower non-targeted organ toxicity...
November 20, 2017: Current Medicinal Chemistry
https://www.readbyqxmd.com/read/29164196/supramolecular-polymeric-biomaterials
#7
REVIEW
Joseph L Mann, Anthony C Yu, Gillie Agmon, Eric A Appel
Polymeric chains crosslinked through supramolecular interactions-directional and reversible non-covalent interactions-compose an emerging class of modular and tunable biomaterials. The choice of chemical moiety utilized in the crosslink affords different thermodynamic and kinetic parameters of association, which in turn illustrate the connectivity and dynamics of the system. These parameters, coupled with the choice of polymeric architecture, can then be engineered to control environmental responsiveness, viscoelasticity, and cargo diffusion profiles, yielding advanced biomaterials which demonstrate rapid shear-thinning, self-healing, and extended release...
November 22, 2017: Biomaterials Science
https://www.readbyqxmd.com/read/29163912/magnetically-activated-adhesives-towards-on-demand-magnetic-triggering-of-selected-polymerisation-reactions
#8
Gemma-Louise Davies, Joseph Govan, Renata Tekoriute, Raquel Serrano-García, Hugo Nolan, David Farrell, Ory Hajatpour, Yurii K Gun'ko
On-demand initiation of chemical reactions is becoming increasingly popular in many areas. The use of a magnetic field to trigger reactions is an intriguing concept, with vast potential in both research and industrial settings, though it remains a challenge as yet unsolved. Here we report the first example of on-demand magnetic activation of a polymerisation process using an anaerobic adhesive formulation as an example of this new approach toward triggering polymerisation reactions using an external magnetic field...
November 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/29161677/nanotechnology-based-recent-approaches-for-sensing-and-remediation-of-pesticides
#9
REVIEW
Deepak Rawtani, Nitasha Khatri, Sanjiv Tyagi, Gaurav Pandey
Pesticides are meant to control and destroy the pests and weeds. They are classified into different categories on the basis their origin and type of pest they target. Chemical pesticides such as insecticides, herbicides and fungicides are commonly used in agricultural fields. However, the excessive use of these agrochemicals have adverse effects on environment such as reduced population of insect pollinators, threat to endangered species and habitat of birds. Upon consumption; chemical pesticides also cause various health issues such as skin, eye and nervous system related problems and cancer upon prolonged exposure...
November 18, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/29161280/microbial-caddisfly-bioherm-association-from-the-lower-cretaceous-shinekhudag-formation-mongolia-earliest-record-of-plant-armoring-in-fossil-caddisfly-cases
#10
Tsolmon Adiya, Cari L Johnson, Mark A Loewen, Kathleen A Ritterbush, Kurt N Constenius, Cory M Dinter
Caddisfly larvae construct underwater protective cases using surrounding materials, thus providing information on environmental conditions in both modern and ancient systems. Microbial bioherms associated with caddisfly cases are found in the Berriassian-Hauterivian (~140-130 Ma) Shinekhudag Formation of Mongolia, and yield new insights into aspects of lacustrine paleoecosystems and paleoenvironments. This formation contains the earliest record of plant-armored caddisfly cases and a rare occurrence of microbial-caddisfly association from the Mesozoic...
2017: PloS One
https://www.readbyqxmd.com/read/29160773/rationalizing-substituent-effects-in-1-azathioxanthone-photophysics
#11
Anne Kathrine R Junker, Thomas Just Sørensen
The influence of an electron donating substituent on the photophysical properties of 1-azathioxanthone dyes has been investigated using optical spectroscopy and theoretical models. The motivation behind the study is based on the fact that thioxanthones are efficient triplet sensitizers, and thus promising sensitizers for lanthanide centered emission. By adding an aza group to one of the phenyl ring systems, direct coordination to a lanthanide center becomes possible, which makes azathoixanthones great candidates as antenna chromophores in lanthanide(III) based dyes...
November 21, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/29158398/model-driven-engineering-of-supramolecular-buffering-by-multivalency
#12
Tim F E Paffen, Abraham J P Teunissen, Tom F A de Greef, E W Meijer
A supramolecular system in which the concentration of a molecule is buffered over several orders of magnitude is presented. Molecular buffering is achieved as a result of competition in a ring-chain equilibrium of multivalent ureidopyrimidinone monomers and a monovalent naphthyridine molecule which acts as an end-capper. While we previously only considered divalent ureidopyrimidinone monomers we now present a model-driven engineering approach to improve molecular buffering using multivalent ring-chain systems...
November 20, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29153876/real-time-evaluation-of-natural-organic-matter-deposition-processes-onto-model-environmental-surfaces
#13
Wenlu Li, Peng Liao, Trey Oldham, Yi Jiang, Chao Pan, Songhu Yuan, John D Fortner
Natural organic matter (NOM) is ubiquitous in aqueous systems and dynamically partitions onto/from environmental surfaces. However, such interfacial processes have not been uniformly quantified in situ and in real time. In this work, adsorption and deposition processes of Suwannee River humic acid (SRHA) and Suwannee River fulvic acid (SRFA), as model NOM, were evaluated for a series of environmentally relevant interfaces. Real-time, interfacial phenomenon, including deposition, release, and adlayer viscoelastic properties, were quantified over a variety of water chemistries via quartz crystal microbalance with dissipation monitoring (QCM-D)...
November 9, 2017: Water Research
https://www.readbyqxmd.com/read/29151576/mapping-the-sugar-dependency-for-rational-generation-of-a-dna-rna-hybrid-guided-cas9-endonuclease
#14
Fernando Orden Rueda, Michal Bista, Matthew D Newton, Anne U Goeppert, M Emanuela Cuomo, Euan Gordon, Felix Kröner, Jon A Read, Jonathan D Wrigley, David Rueda, Benjamin J M Taylor
The CRISPR-Cas9 RNA-guided endonuclease system allows precise and efficient modification of complex genomes and is continuously developed to enhance specificity, alter targeting and add new functional moieties. However, one area yet to be explored is the base chemistry of the associated RNA molecules. Here we show the design and optimisation of hybrid DNA-RNA CRISPR and tracr molecules based on structure-guided approaches. Through careful mapping of the ribose requirements of Cas9, we develop hybrid versions possessing minimal RNA residues, which are sufficient to direct specific nuclease activity in vitro and in vivo with reduced off-target activity...
November 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/29149739/removal-of-tio2-nanoparticles-from-water-by-low-pressure-pilot-plant-filtration
#15
Josune Olabarrieta, Oihane Monzón, Yolanda Belaustegui, Jon-Iñaki Alvarez, Saioa Zorita
Rising use of nanoparticles in manufacturing as well as in commercial products bring issues related to environmental release and human exposure. A large amount of TiO2 nanoparticles will eventually reach wastewater treatment plants. Low pressure membrane filtration has been suggested as a feasible treatment of water streams. This study investigated first at laboratory scale the influence of: i) membrane material, ii) pore size and iii) water chemistry on nTiO2 removal. TiO2 retention was governed by the cake layer formation mechanism and significant retention of nanoparticles was observed even for filters having considerably larger pores than nTiO2...
November 14, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/29149720/a-robust-strategy-for-preparation-of-sequential-stimuli-responsive-block-copolymer-prodrugs-via-thiolactone-chemistry-to-overcome-multiple-anticancer-drug-delivery-barriers
#16
Wendong Ke, Wei Yin, Zengshi Zha, Jean Felix Mukerabigwi, Weijian Chen, Yuheng Wang, Chuanxin He, Zhishen Ge
Block copolymer prodrugs (BCPs) have attracted considerable attentions in clinical translation of nanomedicine owing to their self-assembly into well-defined core-shell nanoparticles for improved pharmacokinetics, stability in blood circulation without drug leakage, and optimized biodistribution. However, a cascade of physiological barriers against specific delivery of drugs into tumor cells limit the final therapeutic efficacy. Herein, we report a robust and facile strategy based on thiolactone chemistry to fabricate well-defined BCPs with sequential tumor pH-promoted cellular internalization and intracellular stimuli-responsive drug release...
November 9, 2017: Biomaterials
https://www.readbyqxmd.com/read/29149517/resolving-a-reactive-organometallic-intermediate-from-dynamic-directing-group-systems-by-selective-c-h-activation
#17
Fredrik Schaufelberger, Brian J J Timmer, Olof Ramström
Catalyst discovery from systems of potential precursors is a challenging endeavor. Herein, a new strategy applying dynamic chemistry to the identification of catalyst precursors from C-H activation of imines is proposed and evaluated. Using hydroacylation of imines as a model reaction, the selection of an organometallic reactive intermediate from a dynamic imine system, involving many potential directing group/metal entities, is demonstrated. The identity of the amplified reaction intermediate with the best directing group could be resolved in situ via ESI-MS, and coupling of the procedure to an iterative deconvolution protocol generated a system with high screening efficiency...
November 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29148757/cross-linked-artificial-enzyme-crystals-as-heterogeneous-catalysts-for-oxidation-reactions
#18
Sarah Lopez, Laurianne Rondot, Chloé Leprêtre, Caroline Marchi-Delapierre, Stéphane Ménage, Christine Cavazza
Designing systems that merge the advantages of heterogeneous catalysis, enzymology and molecular catalysis represents the next major goal for sustainable chemistry. Cross-linked enzyme crystals display most of these essential assets (well-designed mesoporous support, protein selectivity, molecular recognition of substrates). Nevertheless, a lack of reaction diversity, particularly in the field of oxidation, remains a constraint for their increased use in the field. Here, thanks to the design of cross-linked artificial non-heme iron oxygenase crystals, we filled this gap by developing bio-based heterogeneous catalysts capable of oxidizing carbon-carbon double bonds...
November 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29148746/keto-enol-tautomerization-triggers-an-electrophilic-aldehyde-deformylation-reaction-by-a-nonheme-manganese-iii-peroxo-complex
#19
Fabián G Cantú Reinhard, Prasenjit Barman, Gourab Mukherjee, Jitendra Kumar, Deep Kumar, Devesh Kumar, Chivukula V Sastri, Sam P de Visser
Oxygen atom transfer by high-valent enzymatic intermediates remains an enigma in chemical catalysis. In particular, manganese is an important first-row metal involved in key biochemical processes including the biosynthesis of mo-lecular oxygen (through the photosystem II complex) and biodegradation of toxic superoxide to hydrogen peroxide by superoxide dismutase. Biomimetic models of these biological systems have been developed to gain understanding on the structure and properties of short-lived intermediates but also with the aim to create environmentally benign oxidants...
November 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29148732/photocontrolled-release-of-doxorubicin-conjugated-through-a-thioacetal-photocage-in-folate-targeted-nanodelivery-systems
#20
Pamela T Wong, Shengzhuang Tang, Jayme Cannon, Dexin Chen, Rachel Sun, Jennifer Lee, James Phan, Ke Tao, Kang Sun, Biqiong Chen, James R Baker, Seok Ki Choi
Despite their proven ability for precise and targeted release, nanoplatform systems for photocontrolled delivery often face formidable synthetic challenges, in part, due to the paucity of advanced linker strategies. Here we report on a novel linker strategy using a thioacetal ortho-nitrobenzaldehyde (TNB) cage, demonstrating its application for delivery of doxorubicin (Dox) in two nanoscale systems. This photocleavable linker, TNB(OH), which presents two identical arms, each terminated with a hydroxyl functionality, was prepared in a single step from 6-nitroverataldehyde...
November 17, 2017: Bioconjugate Chemistry
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