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https://www.readbyqxmd.com/read/28230869/a-combined-high-temperature-experimental-and-theoretical-kinetic-study-of-the-reaction-of-dimethyl-carbonate-with-oh-radicals
#1
Fethi Khaled, Binod Raj Giri, Milán Szőri, Tam V-T Mai, Lam K Huynh, Aamir Farooq
The reaction kinetics of dimethyl carbonate (DMC) and OH radicals were investigated behind reflected shock waves over the temperature range of 872-1295 K and at pressures near 1.5 atm. Reaction progress was monitored by detecting OH radicals at 306.69 nm using a UV laser absorption technique. The rate coefficients for the reaction of DMC with OH radicals were extracted using a detailed kinetic model developed by Glaude et al. (Proc. Combust. Inst. 2005, 30(1), 1111-1118). The experimental rate coefficients can be expressed in Arrhenius form as: kexpt'l = 5...
February 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28229634/biochemical-characterization-of-the-native-%C3%AE-carbonic-anhydrase-purified-from-the-mantle-of-the-mediterranean-mussel-mytilus-galloprovincialis
#2
Rosa Perfetto, Sonia Del Prete, Daniela Vullo, Giovanni Sansone, Carmela Barone, Mosè Rossi, Claudiu T Supuran, Clemente Capasso
A α-carbonic anhydrase (CA, EC 4.2.1.1) has been purified and characterized biochemically from the mollusk Mytilus galloprovincialis. As in most mollusks, this α-CA is involved in the biomineralization processes leading to the precipitation of calcium carbonate in the mussel shell. The new enzyme had a molecular weight of 50 kDa, which is roughly two times higher than that of a monomeric α-class enzyme. Thus, Mytilus galloprovincialis α-CA is either a dimer, or similar to the Tridacna gigas CA described earlier, may have two different CA domains in its polypeptide chain...
December 2017: Journal of Enzyme Inhibition and Medicinal Chemistry
https://www.readbyqxmd.com/read/28228111/antimicrobial-structure-activity-relationship-of-five-anthraquinones-of-emodine-type-isolated-from-vismia-laurentii
#3
Gislaine Aurelie Kemegne, Pierre Mkounga, Jean Justin Essia Ngang, Sylvain Leroy Sado Kamdem, Augustin Ephrem Nkengfack
BACKGROUND: Antimicrobial activity of anthraquinone compounds of emodine type has been reported by many authors. These compounds are found in Vismia laurentii (Clusiaceae), a plant used in traditional pharmacopoeia for treatment of microbial infections among others affections. The continuous identification of new compounds has raised the problem of the relation between the structure and antimicrobial properties. RESULTS: The yeast growth kinetics parameters were not influenced by the pH variation as it was the case for the other tested bacteria...
February 22, 2017: BMC Microbiology
https://www.readbyqxmd.com/read/28225274/a-rational-design-of-a-selective-inhibitor-for-kv1-1-channels-prevalent-in-demyelinated-nerves-that-improves-their-impaired-axonal-conduction
#4
Ahmed Al-Sabi, Declan Daly, Patrick Hoefer, Gemma K Kinsella, Charles P E Metais, Mark Pickering, Caroline Herron, Seshu Kumar Kaza, Kieran J Nolan, J Oliver Dolly
K(+) channels containing Kv1.1 α subunits, which become prevalent at internodes in demyelinated axons, may underlie their dysfunctional conduction akin to muscle weakness in multiple sclerosis. Small inhibitors were sought with selectivity for the culpable hyper-polarising K(+) currents. Modelling of interactions with the extracellular pore in a Kv1.1 deduced-structure identified a diaryldi-(2-pyrrolyl)methane (DPM) as a suitable scaffold, with optimised alkyl ammonium side chains. The resultant synthesised candidate [2,2'-((5,5'(di-p-topyldiaryldi-(2-pyrrolyl)methane)bis(2,2'carbonyl)bis (azanediyl)) diethaneamine...
February 22, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28224918/remodeling-of-pectin-and-hemicelluloses-in-tomato-pericarp-during-fruit-growth
#5
Fabienne Guillon, Adeline Moïse, Bernard Quemener, Brigitte Bouchet, Marie-Françoise Devaux, Camille Alvarado, Marc Lahaye
Tomato fruit texture depends on histology and cell wall architecture, both under genetic and developmental controls. If ripening related cell wall modifications have been well documented with regard to softening, little is known about cell wall construction during early fruit development. Identification of key events and their kinetics with regard to tissue architecture and cell wall development can provide new insights on early phases of texture elaboration. In this study, changes in pectin and hemicellulose chemical characteristics and location were investigated in the pericarp tissue of tomato (Solanum lycopersicon var Levovil) at four stages of development (7, 14 and 21day after anthesis (DPA) and mature green stages)...
April 2017: Plant Science: An International Journal of Experimental Plant Biology
https://www.readbyqxmd.com/read/28222597/mechanochemical-kinetics-in-elastomeric-polymer-networks-heterogeneity-of-local-forces-results-in-nonexponential-kinetics
#6
Ramesh Adhikari, Dmitrii E Makarov
A common approach to inducing selective mechanochemical transformations relies on embedding the target molecules (called mechanophores) within elastomeric polymer networks. Mechanical properties of such elastomers can also be modulated through the mechanochemical response of the constituent polymer chains. The inherent randomness in the molecular structure of such materials leads to heterogeneity of the local forces exerted on individual mechanophores. Here we use coarse-grained simulations to study the force distributions within random elastomeric networks and show that those distributions are close to exponential regardless of the applied macroscopic load, entanglement effects and/or network parameters...
February 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28221161/morphology-directed-self-assembly-and-pattern-transfer-from-a-high-molecular-weight-polystyrene-block-poly-dimethylsiloxane-block-copolymer-film
#7
Li-Chen Cheng, Wubin Bai, Eduardo Martin, Kun-Hua Tu, Konstantinos Ntetsikas, George Liontos, Apostolos Avgeropoulos, Caroline Ross
The self-assembly of block copolymers with large feature sizes is inherently challenging as the large kinetic barrier arising from chain entanglement of high molecular weight polymers limits the extent over which long-range ordered microdomains can be achieved. Here, we illustrate the evolution of thin film morphology from a diblock copolymer of polystyrene-block-poly(dimethylsiloxane) exhibiting total number average molecular weight of 123 kg/mol, and demonstrate the formation of layers of well-ordered cylindrical microdomains under appropriate conditions of binary solvent mix ratio, commensurate film thickness, and solvent vapor annealing time...
February 21, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28221030/control-of-grafting-density-and-distribution-in-graft-polymers-by-living-ring-opening-metathesis-copolymerization
#8
Tzu-Pin Lin, Alice B Chang, Hsiang-Yun Chen, Allegra L Liberman-Martin, Christopher M Bates, Matthew J Voegtle, Christina A Bauer, Robert H Grubbs
Control over polymer sequence and architecture is crucial to both understanding structure-property relationships and designing functional materials. In pursuit of these goals, we developed a new synthetic approach that enables facile manipulation of the density and distribution of grafts in polymers via living ring-opening metathesis polymerization (ROMP). Discrete endo,exo-norbornenyl dialkylesters (dimethyl DME, diethyl DEE, di-n-butyl DBE) were strategically designed to copolymerize with a norbornene-functionalized polystyrene (PS), polylactide (PLA), or polydimethylsiloxane (PDMS) macromonomer mediated by the 3rd generation catalyst (G3)...
February 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28218850/impact-of-phosphorylation-and-pseudo-phosphorylation-on-the-early-stages-of-aggregation-of-the-microtubule-associated-protein-tau
#9
Dmitriy V Prokopovich, John W Whittaker, Micaiah M Muthee, Azka Ahmed, Luca Larini
The microtubule associated protein tau regulates the stability of microtubules within neurons in the central nervous system. In turn, microtubules are responsible for the remodeling of the cytoskeleton that ultimately leads to the formation or pruning of new connections among neurons. As a consequence, dysfunction of tau is associated with many forms of dementia as well as Alzheimer's disease. In the brain, tau activity is regulated by its phosphorylation state. Phosphorylation is a post-translational modification of proteins that adds a phosphate group to the side chain of an amino acid...
February 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28218829/kinetics-of-polymer-fullerene-phase-separation-during-solvent-annealing-studied-by-table-top-x-ray-scattering
#10
Karol Vegso, Peter Siffalovic, Matej Jergel, Peter Nadazdy, Vojtech Nádaždy, Eva Majkova
Solvent annealing is an efficient way of phase separation in polymer-fullerene blends to optimize bulk heterojunction morphology of active layer in polymer solar cells. To track the process in real time across all relevant stages of solvent evaporation, laboratory-based in-situ small- and wide-angle X-ray scattering measurements were applied simultaneously to a model P3HT:PCBM blend dissolved in dichlorobenzene. The PCBM molecule agglomeration starts at ≈7 wt% concentration of solid content of the blend in solvent...
February 20, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28217423/test-retest-reliability-of-the-closed-kinetic-chain-upper-extremity-stability-test-ckcuest-in-adolescents-reliability-of-ckcuest-in-adolescents
#11
Valéria M A de Oliveira, Ana C R Pitangui, Vinícius Y S Nascimento, Hítalo A da Silva, Muana H P Dos Passos, Rodrigo C de Araújo
BACKGROUND: The Closed Kinetic Chain Upper Extremity Stability Test (CKCUEST) has been proposed as an option to assess upper limb function and stability; however, there are few studies that support the use of this test in adolescents. PURPOSE: The purpose of the present study was to investigate the intersession reliability and agreement of three CKCUEST scores in adolescents and establish clinimetric values for this test. STUDY DESIGN: Test-retest reliability...
February 2017: International Journal of Sports Physical Therapy
https://www.readbyqxmd.com/read/28217412/exercises-that-facilitate-optimal-hamstring-and-quadriceps-co-activation-to-help-decrease-acl-injury-risk-in-healthy-females-a-systematic-review-of-the-literature
#12
Rachel Dedinsky, Lindsey Baker, Samuel Imbus, Melissa Bowman, Leigh Murray
BACKGROUND: Anterior cruciate ligament (ACL) injury is common among females due to many anatomic, hormonal, and neuromuscular risk factors. One modifiable risk factor that places females at increased risk of ACL injury is a poor hamstrings: quadriceps (H:Q) co-activation ratio, which should be 0.6 or greater in order to decrease the stress placed on the ACL. Exercises that produce more quadriceps dominant muscle activation can add to the tension placed upon the ACL, potentially increasing the risk of ACL injury...
February 2017: International Journal of Sports Physical Therapy
https://www.readbyqxmd.com/read/28216792/effect-of-monomer-solubility-on-the-evolution-of-copolymer-morphology-during-polymerization-induced-self-assembly-in-aqueous-solution
#13
Amy A Cockram, Thomas J Neal, Matthew J Derry, Oleksandr O Mykhaylyk, Neal S J Williams, Martin W Murray, Simon N Emmett, Steven P Armes
Polymerization-induced self-assembly (PISA) has become a widely used technique for the rational design of diblock copolymer nano-objects in concentrated aqueous solution. Depending on the specific PISA formulation, reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization typically provides straightforward access to either spheres, worms, or vesicles. In contrast, RAFT aqueous emulsion polymerization formulations often lead to just kinetically-trapped spheres. This limitation is currently not understood, and only a few empirical exceptions have been reported in the literature...
February 14, 2017: Macromolecules
https://www.readbyqxmd.com/read/28216654/performance-kinetic-and-biodegradation-pathway-evaluation-of-anaerobic-fixed-film-fixed-bed-reactor-in-removing-phthalic-acid-esters-from-wastewater
#14
Ehsan Ahmadi, Samira Yousefzadeh, Mohsen Ansari, Hamid Reza Ghaffari, Ali Azari, Mohammad Miri, Alireza Mesdaghinia, Ramin Nabizadeh, Babak Kakavandi, Peyman Ahmadi, Mojtaba Yegane Badi, Mitra Gholami, Kiomars Sharafi, Mostafa Karimaei, Mahboobeh Ghoochani, Masoud Binesh Brahmand, Seyed Mohsen Mohseni, Maryam Sarkhosh, Soheila Rezaei, Hosseinali Asgharnia, Emad Dehghanifard, Behdad Jafari, Alireza Mortezapour, Vahid Kazemi Moghaddam, Mohammad Molla Mahmoudi, Nader Taghipour
Emerging and hazardous environmental pollutants like phthalic acid esters (PAEs) are one of the recent concerns worldwide. PAEs are considered to have diverse endocrine disrupting effects on human health. Industrial wastewater has been reported as an important environment with high concentrations of PAEs. In the present study, four short-chain PAEs including diallyl phthalate (DAP), diethyl phthalate (DEP), dimethyl phthalate (DMP), and phthalic acid (PA) were selected as a substrate for anaerobic fixed film fixed bed reactor (AnFFFBR)...
February 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28216002/stealth-nanocarriers-based-sterosomes-using-peg-post-insertion-process
#15
Anna Cieślak, Nathalie Wauthoz, Alejandro Nieto Orellana, Nolwenn Lautram, Jérôme Béjaud, José Hureaux, Michel Lafleur, Jean-Pierre Benoit, Claudio J Salomon, Guillaume Bastiat
Sterosomes (STEs), a new and promising non-phospholipidic liposome platform based on palmitic acid (PA) and cholesterol (Chol) mixtures, need to have polyethylene glycol (PEG) chains grafted to their surface in order to obtain long-circulating nanocarriers in the blood stream. A post-insertion method was chosen to achieve this modification. The post-insertion process of PEG-modified distearoylphosphoethanolamine (DSPE-PEG) was monitored using the zeta potential value of STEs. Various conditions including PEG chain length and the DSPE-PEG/PA-Chol ratio, were explored...
February 16, 2017: European Journal of Pharmaceutics and Biopharmaceutics
https://www.readbyqxmd.com/read/28213716/density-functional-theory-study-of-the-mechanism-for-the-formation-of-glycidyl-esters-from-triglyceride
#16
Quanyu Wang, Zhuan Ji, Bo Han
Glycidyl fatty acid esters (GEs) are by-products of edible oil refinement that have attracted attention globally due to concerns over their possible harmful effects on human health when consumed. It is thus important to improve our understanding of GE formation if we are to suppress GE production during edible oil refinement. In this paper, a first-principles density functional theory study of the formation mechanism of GEs was performed. Triglycerides undergo a self-condensation reaction between two adjacent ester groups to yield GEs and an anhydride as a by-product...
March 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28209804/long-chain-acyl-coa-synthetase-isoforms-differ-in-preferences-for-eicosanoid-species-and-long-chain-fatty-acids
#17
Eric L Klett, Shufen Chen, Alekhya Yechoor, Fred B Lih, Rosalind A Coleman
Because the signaling eicosanoids, epoxyeicosatrienoic acids (EETs) and hydroxyeicosatetraenoic acids (HETEs), are esterified to membrane phospholipids, we asked which long-chain acyl-CoA synthetase (ACSL) isoforms would activate these molecules and whether the apparent fatty acid substrate preferences of each ACSL isoform might differ depending on whether it was assayed in mammalian cell membranes or as a purified bacterial recombinant protein. We found that all five ACSL isoforms were able to use EETs and HETEs as substrates and showed by LC-MS that ACSLs produce EET-CoAs...
February 16, 2017: Journal of Lipid Research
https://www.readbyqxmd.com/read/28208386/statistical-model-of-a-flexible-inextensible-polymer-chain-the-effect-of-kinetic-energy
#18
V M Pergamenshchik, A B Vozniak
Because of the holonomic constraints, the kinetic energy contribution in the partition function of an inextensible polymer chain is difficult to find, and it has been systematically ignored. We present the first thermodynamic calculation incorporating the kinetic energy of an inextensible polymer chain with the bending energy. To explore the effect of the translation-rotation degrees of freedom, we propose and solve a statistical model of a fully flexible chain of N+1 linked beads which, in the limit of smooth bending, is equivalent to the well-known wormlike chain model...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28208313/diffusion-of-a-rouse-chain-in-porous-media-a-mode-coupling-theory-study
#19
Huai Ding, Huijun Jiang, Nanrong Zhao, Zhonghuai Hou
We use a kinetic mode-coupling theory (MCT) combining with generalized Langevin equation (GLE) to study the diffusion and conformational dynamics of a bead-spring Rouse chain (RC) dissolved in porous media. The media contains fluid particles and immobile matrix ones wherein the latter leads to the lack of translational invariance. The friction kernel ζ(t) used in the GLE can be obtained directly by adopting a simple density-functional approach in which the density correlators calculated by MCT equations of porous media serve as inputs...
January 2017: Physical Review. E
https://www.readbyqxmd.com/read/28199083/shape-memory-hydrogels-evolution-of-structural-principles-to-enable-shape-switching-of-hydrophilic-polymer-networks
#20
Candy Löwenberg, Maria Balk, Christian Wischke, Marc Behl, Andreas Lendlein
The ability of hydrophilic chain segments in polymer networks to strongly interact with water allows the volumetric expansion of the material and formation of a hydrogel. When polymer chain segments undergo reversible hydration depending on environmental conditions, smart hydrogels can be realized, which are able to shrink/swell and thus alter their volume on demand. In contrast, implementing the capacity of hydrogels to switch their shape rather than volume demands more sophisticated chemical approaches and structural concepts...
February 15, 2017: Accounts of Chemical Research
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