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https://www.readbyqxmd.com/read/28102675/mechanistic-elucidation-of-zirconium-catalyzed-direct-amidation
#1
Helena Lundberg, Fredrik Tinnis, Jiji Zhang, Andrés G Algarra, Fahmi Himo, Hans Adolfsson
The mechanism of the zirconium-catalyzed condensation of carboxylic acids and amines for direct formation of amides was studied using kinetics, NMR-spectroscopy and DFT-calculations. The reaction is found to be first order with respect to catalyst and has a positive rate dependence on amine concentration and a negative rate dependence on carboxylic acid concentration. Kinetic experiments using Reaction Progress Kinetic Analysis (RPKA) protocols demonstrate that inhibition of the catalyst by the amide product can be avoided using a high amine concentration...
January 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28102477/potential-new-mechanisms-of-pro-arrhythmia-in-arrhythmogenic-cardiomyopathy-focus-on-calcium-sensitive-pathways
#2
REVIEW
C J M van Opbergen, M Delmar, T A B van Veen
Arrhythmogenic cardiomyopathy, or its most well-known subform arrhythmogenic right ventricular cardiomyopathy (ARVC), is a cardiac disease mainly characterised by a gradual replacement of the myocardial mass by fibrous and fatty tissue, leading to dilatation of the ventricular wall, arrhythmias and progression towards heart failure. ARVC is commonly regarded as a disease of the intercalated disk in which mutations in desmosomal proteins are an important causative factor. Interestingly, the Dutch founder mutation PLN R14Del has been identified to play an additional, and major, role in ARVC patients within the Netherlands...
January 19, 2017: Netherlands Heart Journal
https://www.readbyqxmd.com/read/28102351/origins-of-ripples-in-cvd-grown-few-layered-mos2-structures-under-applied-strain-at-atomic-scales
#3
Jin Wang, Raju R Namburu, Madan Dubey, Avinash M Dongare
The potential of the applicability of two-dimensional molybdenum disulfide (MoS2) structures, in various electronics, optoelectronics, and flexible devices requires a fundamental understanding of the effects of strain on the electronic, magnetic and optical properties. Particularly important is the recent capability to grow large flakes of few-layered structures using chemical vapor deposition (CVD) wherein the top layers are relatively smaller in size than the bottom layers, resulting in the presence of edges/steps across adjacent layers...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28102327/super-strong-materials-for-temperatures-exceeding-2000%C3%A2-%C3%A2-c
#4
Laura Silvestroni, Hans-Joachim Kleebe, William G Fahrenholtz, Jeremy Watts
Ceramics based on group IV-V transition metal borides and carbides possess melting points above 3000 °C, are ablation resistant and are, therefore, candidates for the design of components of next generation space vehicles, rocket nozzle inserts, and nose cones or leading edges for hypersonic aerospace vehicles. As such, they will have to bear high thermo-mechanical loads, which makes strength at high temperature of great importance. While testing of these materials above 2000 °C is necessary to prove their capabilities at anticipated operating temperatures, literature reports are quite limited...
January 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28101732/the-analysis-of-knee-joint-loading-during-drop-landing-from-different-heights-and-under-different-instruction-sets-in-healthy-males
#5
Dmitry Verniba, Jason D Vescovi, David A Hood, William H Gage
BACKGROUND: Mechanical loading during exercise has been shown to promote tissue remodeling. Safe and accessible exercise may be beneficial to populations at risk of diminished bone and joint health. We examined the effect of drop height and instruction on knee loading during a drop-landing task and proposed a task that makes use of drop heights that may be appropriate for rehabilitation purposes and functional in daily life to examine transient knee joint loads. METHODS: Twenty males (22...
December 2017: Sports Medicine—Open
https://www.readbyqxmd.com/read/28101177/analysis-on-mechanism-of-atp-sensitive-k-channel-opener-natakalim-improving-congestive-heart-failure-after-myocardial-infarction
#6
Feng Jin
The action mechanism of natakalim, a novel ATP-sensitive potassium channel opener, was studied in ameliorating the congestive heart failure (CHF) after myocardial infarction. A total of 25 healthy Wistar male rats (age, 10 weeks; average weight, 300 g) were selected, and the CHF models after acute myocardial infarction (AMI) were prepared by ligation of left anterior descending branch. They were randomly divided into the sham operation group, the model group and the groups of 1, 3 and 9 mg/kg/day natakalims...
December 2016: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/28101145/impact-of-physical-activity-and-mechanical-loading-on-biomarkers-typically-used-in-osteoarthritis-assessment-current-concepts-and-knowledge-gaps
#7
REVIEW
Nicole M Cattano, Jeffrey B Driban, Kenneth L Cameron, Michael R Sitler
There is an ongoing need to develop prognostic and diagnostic biomarkers for osteoarthritis (OA). Understanding how biomarkers change in response to physical activity may be vital for understanding if a patient has a joint that is failing to adapt to a given loading stimulus. The purpose of this review is to describe how biomarker changes after joint loading may help detect early OA and determine prognosis. This may help to inform and more specifically target interventions and clinical trials. We conducted a critical review of the relevant literature that was published to January 2016...
January 2017: Therapeutic Advances in Musculoskeletal Disease
https://www.readbyqxmd.com/read/28100643/fluid-shear-stress-increases-transepithelial-transport-of-ca2-in-ciliated-distal-convoluted-and-connecting-tubule-cells
#8
Sami G Mohammed, Francisco J Arjona, Femke Latta, René J M Bindels, Ronald Roepman, Joost G J Hoenderop
In kidney, transcellular transport of Ca(2+) is mediated by transient receptor potential vanilloid 5 and Na(+)-Ca(2+) exchanger 1 proteins in distal convoluted and connecting tubules (DCT and CNT, respectively). It is not yet understood how DCT/CNT cells can adapt to differences in tubular flow rate and, consequently, Ca(2+) load. This study aims to elucidate the molecular mechanisms by which DCT/CNT cells sense fluid dynamics to control transepithelial Ca(2+) reabsorption and whether their primary cilia play an active role in this process...
January 18, 2017: FASEB Journal: Official Publication of the Federation of American Societies for Experimental Biology
https://www.readbyqxmd.com/read/28100256/transcriptomic-signatures-differentiate-survival-from-fatal-outcomes-in-humans-infected-with-ebola-virus
#9
Xuan Liu, Emily Speranza, César Muñoz-Fontela, Sam Haldenby, Natasha Y Rickett, Isabel Garcia-Dorival, Yongxiang Fang, Yper Hall, Elsa-Gayle Zekeng, Anja Lüdtke, Dong Xia, Romy Kerber, Ralf Krumkamp, Sophie Duraffour, Daouda Sissoko, John Kenny, Nichola Rockliffe, E Diane Williamson, Thomas R Laws, Magassouba N'Faly, David A Matthews, Stephan Günther, Andrew R Cossins, Armand Sprecher, John H Connor, Miles W Carroll, Julian A Hiscox
BACKGROUND: In 2014, Western Africa experienced an unanticipated explosion of Ebola virus infections. What distinguishes fatal from non-fatal outcomes remains largely unknown, yet is key to optimising personalised treatment strategies. We used transcriptome data for peripheral blood taken from infected and convalescent recovering patients to identify early stage host factors that are associated with acute illness and those that differentiate patient survival from fatality. RESULTS: The data demonstrate that individuals who succumbed to the disease show stronger upregulation of interferon signalling and acute phase responses compared to survivors during the acute phase of infection...
January 19, 2017: Genome Biology
https://www.readbyqxmd.com/read/28100095/shoulder-kinetics-during-start-up-and-propulsion-with-a-manual-wheelchair-within-the-initial-phase-of-uninstructed-training
#10
Samuel Hybois, Alice Siegel, Joseph Bascou, Nicolas Eydieux, Philippe Vaslin, Hélène Pillet, Pascale Fodé, Christophe Sauret
PURPOSE: Wheelchair locomotion is constraining for the upper limbs and involves a set of motor tasks that need to be learnt by a novice user. To understand this integration process, we investigated the evolution of shoulder kinetics during start-up and propulsion within the initial phase of low-intensity uninstructed training. MATERIALS AND METHODS: Seventeen novice able-bodied subjects performed a 120-min uninstructed practice distributed over 4 weeks. During the initial and final sessions, upper limbs kinematics and hand-rim kinetics were continuously collected...
January 19, 2017: Disability and Rehabilitation. Assistive Technology
https://www.readbyqxmd.com/read/28099873/antimicrobial-photodynamic-therapy-as-an-adjunct-for-treatment-of-deep-carious-lesions-a-systematic-review
#11
REVIEW
Fabian Cieplik, Wolfgang Buchalla, Elmar Hellwig, Ali Al-Ahmad, Karl-Anton Hiller, Tim Maisch, Lamprini Karygianni
For deep carious lesions, a more conservative treatment modality ("selective caries removal") has been proposed, where only the heavily contaminated dentine is removed. In this regard, effective adjuncts for cavity disinfection such as the antimicrobial photodynamic therapy (aPDT) can be valuable clinically prior to definitive restoration. Therefore, the aim of this study was to systematically assess clinical studies on the effectiveness of aPDT as a supplementary tool in the treatment of deep caries lesions...
January 15, 2017: Photodiagnosis and Photodynamic Therapy
https://www.readbyqxmd.com/read/28099412/ultrafast-nonthermal-photo-magnetic-recording-in-a-transparent-medium
#12
A Stupakiewicz, K Szerenos, D Afanasiev, A Kirilyuk, A V Kimel
Discovering ways to control the magnetic state of media with the lowest possible production of heat and at the fastest possible speeds is important in the study of fundamental magnetism, with clear practical potential. In metals, it is possible to switch the magnetization between two stable states (and thus to record magnetic bits) using femtosecond circularly polarized laser pulses. However, the switching mechanisms in these materials are directly related to laser-induced heating close to the Curie temperature...
January 18, 2017: Nature
https://www.readbyqxmd.com/read/28098952/solving-the-puzzle-of-one-carbon-loss-in-ripostatin-biosynthesis
#13
Chengzhang Fu, David Auerbach, Yanyan Li, Ullrich Scheid, Eva Luxenburger, Ronald Garcia, Herbert Irschik, Rolf Müller
Ripostatin is a promising antibiotic that inhibits RNA polymerase by binding to a novel binding site. In this study, the characterization of the biosynthetic gene cluster of ripostatin, which is a peculiar polyketide synthase (PKS) hybrid cluster encoding cis- and trans-acyltransferase PKS genes, is reported. Moreover, an unprecedented mechanism for phenyl acetic acid formation and loading as a starter unit was discovered. This phenyl-C2 unit is derived from phenylpyruvate (phenyl-C3) and the mechanism described herein explains the mysterious loss of one carbon atom in ripostatin biosynthesis from the phenyl-C3 precursor...
January 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28098356/mechano-chemo-transduction-in-cardiac-myocytes
#14
Ye Chen-Izu, Leighton T Izu
The heart has the ability to adjust to changing mechanical loads. The Frank-Starling law and the Anrep effect describe exquisite intrinsic mechanisms the heart has for autoregulating the force of contraction to maintain cardiac output under preload and afterload. Although these mechanisms have been known for more than a century, their cellular and molecular underpinnings are still debated. How does the cardiac myocyte sense a change in preload or afterload? How does the myocyte adjust its response to compensate for such changes? In cardiac myocytes Ca(2+) is a crucial regulator of contractile force and in this review we compare and contrast recent results from different labs that address two important questions...
January 18, 2017: Journal of Physiology
https://www.readbyqxmd.com/read/28098316/a-family-of-mechanically-adaptive-supramolecular-graphene-oxide-poly-ethylenimine-hydrogels-from-aqueous-assembly
#15
Chao Wang, Yipin Duan, Nicole S Zacharia, Bryan D Vogt
Composite hydrogels containing graphene oxide (GO) offer advantageous mechanical properties, but tuning these properties generally requires the synthesis of new hydrogels or if the hydrogel is thermally responsive, utilization of a chemistry determined temperature window. Here, we demonstrate a simple route to generate a family of GO-based hydrogels from aqueous solution based assembly of GO with polycationic poly(ethylenimine), PEI, without any secondary chemical crosslinking. Tuning the ratio of GO : PEI during the assembly produces a family of hydrogels that responds to mechanical compression by irreversibly altering their equilibrium water content and mechanical properties in a controllable manner...
January 18, 2017: Soft Matter
https://www.readbyqxmd.com/read/28097936/experimental-study-on-tissue-phantoms-to-understand-the-effect-of-injury-and-suturing-on-human-skin-mechanical-properties
#16
Arnab Chanda, Vinu Unnikrishnan, Zachary Flynn, Kim Lackey
Skin injuries are the most common type of injuries occurring in day-to-day life. A skin injury usually manifests itself in the form of a wound or a cut. While a shallow wound may heal by itself within a short time, deep wounds require surgical interventions such as suturing for timely healing. To date, suturing practices are based on a surgeon's experience and may vary widely from one situation to another. Understanding the mechanics of wound closure and suturing of the skin is crucial to improve clinical suturing practices and also to plan automated robotic surgeries...
January 2017: Proceedings of the Institution of Mechanical Engineers. Part H, Journal of Engineering in Medicine
https://www.readbyqxmd.com/read/28097087/identification-of-the-vascular-endothelial-growth-factor-signalling-pathway-by-quantitative-proteomic-analysis-of-rat-condylar-cartilage
#17
Liting Jiang, Yinyin Xie, Li Wei, Qi Zhou, Xing Shen, Xinquan Jiang, Yiming Gao
Angiogenesis mediated by vascular endothelial growth factor (VEGF) is known to play an important role in regulating cartilage remodelling and endochondral ossification. However, the details of how VEGF signalling mechanisms affect condyle remodelling in response to alterations in functional loading remains unclear. To explore this, eighty 16-day-old male SD rats were divided into two equal groups which were fed either a soft/powdery diet or a hard diet for 4 weeks; the stiffness of the diet results in alteration of mastication force and hence temporomandibular joint (TMJ) development...
January 2017: FEBS Open Bio
https://www.readbyqxmd.com/read/28097085/interaction-with-adenylate-cyclase-toxin-from-bordetella-pertussis-affects-the-metal-binding-properties-of-calmodulin
#18
Tzvia I Springer, Corey C Emerson, Christian W Johns, Natosha L Finley
Adenylate cyclase toxin domain (CyaA-ACD) is a calmodulin (CaM)-dependent adenylate cyclase involved in Bordetella pertussis pathogenesis. Calcium (Ca(2+)) and magnesium (Mg(2+)) concentrations impact CaM-dependent CyaA-ACD activation, but the structural mechanisms remain unclear. In this study, NMR, dynamic light scattering, and native PAGE were used to probe Mg(2+)-induced transitions in CaM's conformation in the presence of CyaA-ACD. Mg(2+) binding was localized to sites I and II, while sites III and IV remained Ca(2+) loaded when CaM was bound to CyaA-ACD...
January 2017: FEBS Open Bio
https://www.readbyqxmd.com/read/28096394/elucidating-the-mechanism-of-fluorinated-extender-unit-loading-for-improved-production-of-fluorine-containing-polyketides
#19
Omer Ad, Benjamin W Thuronyi, Michelle C Y Chang
Polyketides are a large family of bioactive natural products synthesized by polyketide synthase (PKS) enzyme complexes predominantly from acetate and propionate. Given the structural diversity of compounds produced using these two simple building blocks, there has been longstanding interest in engineering the incorporation of alternative extender units. We have been investigating the mechanism of fluorinated monomer insertion by three of the six different modules of the PKS involved in erythromycin biosynthesis (6-deoxyerythronolide B synthase, DEBS) to begin understanding the contribution of different steps, such as enzyme acylation, transacylation, C-C bond formation, and chain transfer, to the overall selectivity and efficiency of this process...
January 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28095983/application-of-close-packed-structures-in-dental-resin-composites
#20
Ruili Wang, Eric Habib, X X Zhu
OBJECTIVE: The inorganic filler particles in dental resin composites serve to improve their mechanical properties and reduce polymerization shrinkage during their use. Efforts have been made in academia and industry to increase the filler particle content, but, few studies examine the theoretical basis for the maximum particle loading. METHODS: This work evaluates the packing of spherical particles in a close-packed state for highly loaded composites. RESULTS: Calculations show that for low dispersity particles, the maximum amount of particles is 74...
January 14, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
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