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https://www.readbyqxmd.com/read/28738023/cluster-assembly-route-to-a-novel-octagonal-two-dimensional-zno-monolayer
#1
Prashant V Gaikwad, Pradeep K Pujari, Sudip Chakroborty, Anjali Kshirsagar
To explore the possibility of cluster assembly resulting in a two-dimensional (2D) stable monolayer of ZnO, a systematic study is performed on the structural evolution of bare and passivated stoichiometric clusters of [Formula: see text] [Formula: see text], [Formula: see text], using density-functional-theory-based first principles electronic structure calculations. The changes in hybridization are investigated with the aid of the site-projected partial density of states and partial charge density, while the effect of passivation and size on the ionicity of the cluster is studied using Bader charge analysis...
July 24, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28737928/electron-beam-etching-of-cao-crystals-observed-atom-by-atom
#2
Yuting Shen, Tao Xu, Xiaodong Tan, Jun Sun, Longbing He, Kuibo Yin, Yilong Zhou, Florian Banhart, Litao Sun
With the rapid development of nanoscale structuring technology, the precision in the etching reaches the sub-10 nm scale today. However, with the ongoing development of nanofabrication, the etching mechanisms with atomic precision still have to be understood in detail and improved. Here we observe atom by atom how preferential facets form in CaO crystals that are etched by an electron beam in an in situ high resolution transmission electron microscope (HRTEM). An etching mechanism under electron beam irradiation is observed that is surprisingly similar to chemical etching and results in the formation of nano-facets...
July 24, 2017: Nano Letters
https://www.readbyqxmd.com/read/28737926/geometric-shape-regulation-and-non-covalent-synthesis-of-one-dimensional-organic-luminescent-nano-micro-materials
#3
Xiaoxian Song, Zuolun Zhang, Shou-Feng Zhang, Jinbei Wei, Kaiqi Ye, Yu Liu, Todd B Marder, Yue Wang
Non-covalent synthesis of one-dimensional (1D) organic nano/micro-materials with controllable geometric shapes or morphologies and special luminescent/electronic properties is one of the greatest challenges in modern chemistry and material science. Control of non-covalent interactions is fundamental for realizing desired 1D structures and crucial for understanding the functions of these interactions. Here, a series of thiophene-fused phenazines composed of a halogen-substituted π-conjugated plate and a pair of flexible side chains is presented, which displays halogen-dependent 1D self-assemblies...
July 24, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28737912/molecular-structure-equilibrium-conformation-and-ring-puckering-motion-in-1-1-3-3-tetramethylcyclobutane-an-electron-diffraction-investigation-augmented-by-molecular-orbital-and-normal-coordinate-calculations
#4
Kenneth Hedberg, Lise Hedberg, Jason Sandwich
The molecule cyclobutane (CB) has a non-planar carbon skeleton folded around a line connecting diagonally opposite atoms. The puckering angle (the change from planarity) of about 30° is generally attributed to steric repulsion between the four sets of adjacent methylene groups which would be opposed in a planar ring and is relieved by the puckering. According to this criterion, a similar molecule, 1,1,3,3-tetramethylcyclobutene (TMCB), in which adjacent methylene groups do not exist, would be expected to have a planar ring in the equilibrium form...
July 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28737896/interfacial-shear-strength-and-adhesive-behavior-of-silk-ionomer-surfaces
#5
Sunghan Kim, Ren D Geryak, Shuaidi Zhang, Ruilong Ma, Rossella Calabrese, David L Kaplan, Vladimir V Tsukruk
The interfacial shear strength between different layers in multi-layered structures of layer-by-layer (LbL) microcapsules is a crucial mechanical property to ensure their robustness. In this work, we investigated the interfacial shear strength of modified silk fibroin ionomers utilized in LbL shells, an ionic-cationic pair with complimentary ionic pairing, (SF)-poly-L-glutamic acid (Glu) and SF- poly-L-lysine (Lys) and a complementary pair with partially screened Coulombic interactions due to the presence of poly(ethylene glycol) (PEG) segments, SF-Glu/SF-Lys[PEG] pair...
July 24, 2017: Biomacromolecules
https://www.readbyqxmd.com/read/28737802/accurate-prediction-of-energetic-properties-of-ionic-liquid-clusters-using-a-fragment-based-quantum-mechanical-method
#6
Jinfeng Liu, Xiao He
Accurate prediction of physicochemical properties of ionic liquids (ILs) is of great significance to understand and design novel ILs with unique properties. This study employed the electrostatically embedded generalized molecular fractionation (EE-GMF) method for accurate energy calculation of IL clusters. The accuracy and efficiency of the EE-GMF method are systematically assessed at different ab initio levels (including HF, DFT and MP2) with diverse basis sets. With the fixed charge model for the embedding field, the deviations of the EE-GMF approach from conventional full system calculations are within 2...
July 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28737725/optimization-of-the-silver-nanoparticles-peald-process-on-the-surface-of-1-d-titania-coatings
#7
Aleksandra Radtke, Tomasz Jędrzejewski, Wiesław Kozak, Beata Sadowska, Marzena Więckowska-Szakiel, Ewa Talik, Maarit Mäkelä, Markku Leskelä, Piotr Piszczek
Plasma enhanced atomic layer deposition (PEALD) of silver nanoparticles on the surface of 1-D titania coatings, such as nanotubes (TNT) and nanoneedles (TNN), has been carried out. The formation of TNT and TNN layers enriched with dispersed silver particles of strictly defined sizes and the estimation of their bioactivity was the aim of our investigations. The structure and the morphology of produced materials were determined using X-ray photoelectron spectroscopy (XPS) and scanning electron miscroscopy (SEM)...
July 24, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28737462/co-delivery-of-hydrophilic-and-hydrophobic-drugs-by-micelles-a-new-approach-using-drug-conjugated-peg-pcl-nanoparticles
#8
H Danafar, K Rostamizadeh, S Davaran, M Hamidi
Co-delivery strategy has been proposed to minimize the amount of each drug and to achieve the synergistic effect for cancer therapies. A conjugate of the antitumor drug, doxorubicin, with diblock methoxy poly (ethylene glycol)-poly caprolactone (mPEG-PCL) copolymer was synthesized by the reaction of mPEG-PCL copolymer with doxorubicin in the presence of p-nitrophenylchloroformate. The conjugated copolymer was characterized in vitro by (1)H NMR, FTIR, DSC and GPC techniques. Then, the doxorubicin conjugated mPEG-PCL(DOX-mPEG-PCL) was self-assembled into micelles in the presence of curcumin in aqueous solution...
July 24, 2017: Drug Development and Industrial Pharmacy
https://www.readbyqxmd.com/read/28737449/molecular-docking-studies-of-fused-coumarin-derivatives-as-inhibitors-of-glcn-6
#9
Sevdije Govori, Arben Haziri, Kastriot Ademi, Nexhat Neziraj
The biological activity of heterocyclic compounds depends on their structure, the type of hetero atoms in the ring and on the type of substituents present. In this paper, some heterocyclic compounds with coumarin moieties S1-S5 and novobiocin known as coumarin antibiotic were subjected to the molecular docking studies as important tools for drug discovery. Glucosamine-6-phosphate synthase is selected as a suitable target in this study. In silico studies reveal that all synthesized compounds S1-S5 are good inhibitors of GlcN-6 and the docking results are in agreement with in vitro antibacterial evaluation of compounds S1-S5...
July 24, 2017: Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering
https://www.readbyqxmd.com/read/28737405/enhanced-gas-sensitivity-and-sensing-mechanism-of-network-structures-assembled-from-%C3%AE-fe2o3-nanosheets-with-exposed-104-facets
#10
Yong Ma, Juan Yang, Yukun Yuan, Hua Zhao, Qian Shi, Fangjuan Zhang, Cuijin Pei, Bin Liu, Heqing Yang
Network structures assembled from -Fe2O3 nanosheets with exposed {104} facets were successfully prepared by heating Fe(NO3)3 solution containing polyvinyl pyrrolidone (PVP) in air. The -Fe2O3 nanosheets based network structures demonstrate significantly higher response to ethanol and triethylamine than -Fe2O3 sea urchin-like nanostructures and commercial powders. The response to 200 ppb of C2H5OH and 90 ppb of N(C2H5)3 is 1.27 and 1.12, respectively. The excellent sensing performances can be ascribed to the exposed (104) facet terminated with Fe atoms...
July 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28737384/physicochemical-parameters-affecting-the-electrospray-ionization-efficiency-of-amino-acids-after-acylation
#11
Jos Hermans, Sara Ongay, Vadym Markov, Rainer Bischoff
Electrospray ionization (ESI) is widely used in liquid chromatography coupled to mass spectrometry (LC-MS) for the analysis of biomolecules. However, the ESI process is still not completely understood and it is often a matter of trial and error to enhance ESI efficiency and hence the response of a given set of compounds. In this work we performed a systematic study of the ESI response of 14 amino acids that were acylated with organic acid anhydrides of increasing chain length and with polyethylene glycol (PEG) changing certain physicochemical properties in a predictable manner...
July 24, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28737233/direct-observation-of-inherent-atomic-scale-defect-disorders-responsible-for-high-performance-ti1-x-hfx-nisn1-y-sby-half-heusler-thermoelectric-alloys
#12
Ki Sung Kim, Young-Min Kim, Hyeona Mun, Jisoo Kim, Jucheol Park, Albina Y Borisevich, Kyu Hyoung Lee, Sung Wng Kim
Structural defects often dominate the electronic- and thermal-transport properties of thermoelectric (TE) materials and are thus a central ingredient for improving their performance. However, understanding the relationship between TE performance and the disordered atomic defects that are generally inherent in nanostructured alloys remains a challenge. Herein, the use of scanning transmission electron microscopy to visualize atomic defects directly is described and disordered atomic-scale defects are demonstrated to be responsible for the enhancement of TE performance in nanostructured Ti1-x Hfx NiSn1-y Sby half-Heusler alloys...
July 24, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28737182/micro-and-nano-patterned-elastin-like-polypeptide-hydrogels-for-stem-cell-culture
#13
A Paul, M Stührenberg, S Chen, D Rhee, W-K Lee, T W Odom, S C Heilshorn, A Enejder
We show that submicron-sized patterns can be imprinted into soft, recombinant-engineered protein hydrogels (here elastin-like proteins, ELP) by transferring wavy patterns from polydimethylsiloxane (PDMS) molds. The high-precision topographical tunability of the relatively stiff PDMS is translated to a bio-responsive, soft material, enabling topographical cell response studies at elastic moduli matching those of tissues. Aligned and unaligned wavy patterns with mold periodicities of 0.24-4.54 μm were imprinted and characterized by coherent anti-Stokes Raman scattering and atomic force microscopy...
July 24, 2017: Soft Matter
https://www.readbyqxmd.com/read/28737038/evolution-of-aggregate-structure-in-solutions-of-anionic-monorhamnolipids-experimental-and-computational-results
#14
Ryan J Eismin, Elango Munusamy, Laurel L Kegel, David E Hogan, Raina M Maier, Steven D Schwartz, Jeanne E Pemberton
The evolution of solution aggregates of the anionic form of the native monorhamnolipid (mRL) mixture produced by Pseudomonas aeruginosa ATCC 9027 is explored at pH 8.0 using both experimental and computational approaches. Experiments utilizing surface tension measurements, dynamic light scattering, and both steady-state and time-resolved fluorescence spectroscopy reveal solution aggregation properties. All-atom molecular dynamics simulations on self-assemblies of the most abundant monorhamnolipid molecule, l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10), in its anionic state explore the formation of aggregates and the role of hydrogen bonding, substantiating the experimental results...
July 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28737034/modification-of-the-poly-bisdodecylquaterthiophene-pqt12-structure-for-high-and-predominantly-nonionic-conductivity-with-matched-dopants
#15
Hui Li, Mallory E DeCoster, Robert M Ireland, Jian Song, Patrick E Hopkins, Howard E Katz
A series of p-type polymers was synthesized by modifying the structure of poly(bisdodecylquaterthiophene) (PQT12) to increase their oxidizability by p-dopants. A sulfur atom is inserted between the thiophene rings and dodecyl chains, and/or 3,4-ethylenedioxy groups are appended to thiophene rings of PQT12. All the polymers have good solubility in organic solvents and can be formed as active layers in conductive and thermoelectric devices by simply drop casting. Doped with the strong oxidant nitrosonium tetrafluroborate (NOBF4), PQTS12 (with sulfur in side chains) shows a very high conductivity up to 350 S cm-1, the highest reported nonionic conductivity among films made from dopant-polymer solutions...
July 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28737009/non-additive-stabilization-by-halogenated-amino-acids-reveals-protein-plasticity-on-a-sub-angstrom-scale
#16
Azade S Hosseini, Christopher J Pace, Adam A Esposito, Jianmin Gao
It has been a long-standing goal to understand the structure-stability relationship of proteins, as optimal stability is essential for protein function and highly desirable for protein therapeutics. Halogenation has emerged as a minimally invasive strategy to probe the physical characteristics of proteins in solution, as well as enhance the structural stabilities of proteins for therapeutic applications. Although advances in synthetic chemistry and genetic code expansion have allowed for the rapid synthesis of proteins with diverse chemical sequences, much remains to be learned regarding the impact of these mutations on their structural integrity...
July 24, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28736501/design-of-radioiodinated-pharmaceuticals-structural-features-affecting-metabolic-stability-towards-in-vivo-deiodination
#17
REVIEW
Lorenzo Cavina, Dion van der Born, Peter H M Klaren, Martin C Feiters, Otto C Boerman, Floris P J T Rutjes
Radioiodinated pharmaceuticals are convenient tracers for clinical and research investigations because of the relatively long half-lives of radioactive iodine isotopes (i.e., (123)I, (124)I, and (131)I) and the ease of their chemical insertion. Their application in radionuclide imaging and therapy may, however, be hampered by poor in vivo stability of the C-I bond. After an overview of the use of iodine in biology and nuclear medicine, we present here a survey of the catabolic pathways for iodinated xenobiotics, including their biodistribution, accumulation, and biostability...
June 30, 2017: European Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28736176/crystal-structure-of-the-c-terminal-domain-of-human-eif2d-and-its-implications-on-eukaryotic-translation-initiation
#18
Anand T Vaidya, Ivan B Lomakin, Newlyn N Joseph, Sergey E Dmitriev, Thomas A Steitz
Protein synthesis is a key process in all living organisms. In eukaryotes, Initiation Factor 2 (eIF2) plays an important role in translation initiation as it selects and delivers the initiator tRNA to the small ribosomal subunit. Under stress conditions, phosphorylation of the α-subunit of eIF2 downregulates cellular protein synthesis. However, translation of certain mRNAs continues via the eIF2D dependent non-canonical initiation pathway. The molecular mechanism of this process remains elusive. In addition, eIF2D plays a role in translation re-initiation and ribosome recycling...
July 20, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28735221/physicochemical-properties-of-ionic-and-non-ionic-biocompatible-hydrogels-in-water-and-cell-culture-conditions-relation-with-type-of-morphologies-of-bovine-fetal-fibroblasts-in-contact-with-the-surfaces
#19
Rebeca Rivero, Fabrisio Alustiza, Virginia Capella, Cecilia Liaudat, Nancy Rodriguez, Pablo Bosch, Cesar Barbero, Claudia Rivarola
Cationic, anionic and non-ionic hydrogels having acrylamide polymer backbones were synthesized via free radical polymerization with N,N-methylenebisacrylamide (BIS) as crosslinker. The chemical structures of the hydrogels were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Physicochemical properties such as swelling kinetic, maximum swelling capacity, volume phase transition temperature (VPTT) and wettability (static water contact angle) of hydrogels swollen in aqueous and cell culture medium, at room and cell culture temperatures were studied...
July 11, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28735171/encoding-of-coordination-complexes-with-xml
#20
P Vinoth, P Sankar
An in-silico system to encode structure, bonding and properties of coordination complexes is developed. The encoding is achieved through a semantic XML markup frame. Composition of the coordination complexes is captured in terms of central atom and ligands. Structural information of central atom is detailed in terms of electron status of valence electron orbitals. The ligands are encoded with specific reference to the electron environment of ligand centre atoms. Behaviour of ligands to form low or high spin complexes is accomplished by assigning a Ligand Centre Value to every ligand based on the electronic environment of ligand centre atom...
July 13, 2017: Journal of Molecular Graphics & Modelling
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