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kinetic control

Michael J Cooney
Enzyme kinetics is the study of the chemical reactions that are catalyzed by enzymes, with a focus on their reaction rates. The study of an enzyme's kinetics considers the various stages of activity, reveals the catalytic mechanism of this enzyme, correlates its value to assay conditions, and describes how a drug or a poison might inhibit the enzyme. Victor Henri initially reported that enzyme reactions were initiated by a bond between the enzyme and the substrate. By 1910, Michaelis and Menten were advancing their work by studying the kinetics of an enzyme saccharase which catalyzes the hydrolysis of sucrose into glucose and fructose...
2017: Methods in Molecular Biology
Bahtijor Rasulov, Eero Talts, Ulo Niinemets
Plant isoprene emissions respond to light and temperature similarly to photosynthesis, but CO2-dependencies of isoprene emission and photosynthesis are profoundly different with photosynthesis increasing and isoprene emissions decreasing with increasing CO2 concentration due to reasons not yet understood. We studied isoprene emission, net assimilation rate and chlorophyll fluorescence under different CO2 and O2 concentrations in the strong isoprene emitter hybrid aspen (Populus tremula x P. tremuloides), and used rapid changes in ambient CO2 or O2 concentrations or light level to induce oscillations...
October 21, 2016: Plant Physiology
Hung-Yi Liu, Tanja Greene, Tsai-Yu Lin, Camron S Dawes, Murray Korc, Chien-Chi Lin
: The complex network of biochemical and biophysical cues in the pancreatic desmoplasia not only presents challenges to the fundamental understanding of tumor progression, but also hinders the development of therapeutic strategies against pancreatic cancer. Residing in the desmoplasia, pancreatic stellate cells (PSCs) are the major stromal cells affecting the growth and metastasis of pancreatic cancer cells by means of paracrine effects and extracellular matrix protein deposition. PSCs remain in a quiescent/dormant state until they are 'activated' by various environmental cues...
October 18, 2016: Acta Biomaterialia
R Boni, A Gallo, S Cecchini
Owing to the progressive decline of sperm motility during storage there is a need to find substances capable of enhancing sperm energy metabolism and motility and/or preserving it from oxidative damage. The aim of this study was to evaluate in frozen/thawed bovine spermatozoa the effect of several compounds, such as myo-inositol, pentoxifylline, penicillamine + hypotaurine + epinephrine mixture (PHE), caffeine and coenzyme Q10+ zinc + d-aspartate mixture (CZA), on either kinetic or metabolic parameters. Sperm kinetics was evaluated by Sperm Class Analyser whereas specific fluorochromes were used to evaluated mitochondrial membrane potential (MMP), intracellular pH, intracellular calcium concentration and lipid peroxidation...
October 21, 2016: Andrology
Chencheng Sun, Bowen Xiong, Yang Pan, Hao Cui
Polyaniline (PANI) prepared by chemical oxidation was studied for adsorption removal of tannic acid (TA) from aqueous solution. Batch adsorption studies were carried out under different adsorbent dosages, pH, ionic strength, initial TA concentration and coexisting anions. Solution pH had an important impact on TA adsorption onto PANI with optimal removal in the pH range of 8-11. TA adsorption on PANI at three ionic strength levels (0.02, 0.2 and 2molL(-1) NaCl) could be well described by Langmuir model (monolayer adsorption process) and the maximum adsorption capacity was 230, 223 and 1023mgg(-1), respectively...
October 15, 2016: Journal of Colloid and Interface Science
Lindsay V Slater, Joseph M Hart
The squat is an assessment of lower extremity alignment during movement, however there is little information regarding altered joint kinetics during poorly performed squats. The purpose of this study was to examine changes in joint kinetics and power from altered knee alignment during a squat. Thirty participants completed squats while displacing the knee medially, anteriorly, and with neutral alignment (control). Sagittal and frontal plane torques at the ankle, knee, and hip were altered in the descending and ascending phase of the squat in both the medial and anterior malaligned squat compared to the control squat...
October 12, 2016: Journal of Electromyography and Kinesiology
Louis M Luttrell
The ability of structurally distinct ligands to "bias" G protein-coupled receptor signaling affords the opportunity to tailor efficacy to suit specific therapeutic needs. Furness et al. demonstrate that ligand structure controls not only which effectors are activated, but also the way they are activated and the kinetics of downstream signaling.
October 20, 2016: Cell
Katrin Feldbauer, Jan Schlegel, Juliane Weissbecker, Frank Sauer, Phillip G Wood, Ernst Bamberg, Ulrich Terpitz
An optochemokine tandem was developed to control the release of calcium from endosomes into the cytosol by light and to analyze the internalization kinetics of G-protein coupled receptors (GPCRs) by electrophysiology. A previously constructed rhodopsin tandem was re-engineered to combine the light-gated Ca2+-permeable cation channel Channelrhodopsin-2(L132C), CatCh, with the chemokine receptor CXCR4 in a functional tandem protein tCXCR4/CatCh. The GPCR was used as a shuttle protein to displace CatCh from the plasma membrane into intracellular areas...
2016: PloS One
Ruben Perez-Carrasco, Pilar Guerrero, James Briscoe, Karen M Page
During tissue development, patterns of gene expression determine the spatial arrangement of cell types. In many cases, gradients of secreted signalling molecules-morphogens-guide this process by controlling downstream transcriptional networks. A mechanism commonly used in these networks to convert the continuous information provided by the gradient into discrete transitions between adjacent cell types is the genetic toggle switch, composed of cross-repressing transcriptional determinants. Previous analyses have emphasised the steady state output of these mechanisms...
October 2016: PLoS Computational Biology
Lívia R Teixeira, Stelio P L Luna, Lídia M Matsubara, Maria L B Cápua, Bianca P C R Santos, Luciane R Mesquita, Luis G Faria, Felipe S Agostinho, Anna Hielm-Björkman
OBJECTIVE To evaluate pain intensity and kinetic variables in dogs with hip dysplasia (HD) treated with acupuncture, carprofen, or a placebo. DESIGN Randomized, controlled clinical study. ANIMALS 54 HD-affected dogs and 16 healthy dogs. PROCEDURES Seven HD-affected dogs were removed from the study. Dogs with HD were treated in a blinded manner for 30 days with acupuncture (once weekly for 5 sessions; n = 15), carprofen (4.4 mg/kg [2.0 mg/lb], PO, q 24 h; n = 16), or placebo capsules containing lactose (1 mg/kg [0...
November 1, 2016: Journal of the American Veterinary Medical Association
Gil Henkin, Daniel Berard, Francis Stabile, Marjan Shayegan, Jason S Leith, Sabrina R Leslie
We present a dynamically adjustable nanofluidic platform for formatting the conformations of and visualizing the interaction kinetics between biomolecules in solution, offering new time resolution and control of the reaction processes. This platform extends Convex Lens-induced Confinement (CLiC), a technique for imaging molecules under confinement, by introducing a system for in-situ modification of the chemical environment; this system uses a deep microchannel to diffusively exchange reagents within the nanoscale imaging region, whose height is fixed by a nanopost array...
October 21, 2016: Analytical Chemistry
Dureid Qazzazie, Mohammad Halhouli, Olena Yurchenko, Gerald Urban
The lack of performance of graphene-based electrocatalysts for oxygen reduction (ORR) is a major concern for fuel cells which can be mastered using nanocomposites. This work is highlighted by the optimization of nitrogen(N)-doped graphene/carbon nanotubes (CNTs) nanocomposite's ORR performance examined by galvanostatic measurements in realistically approached glucose half-cells. Obtained results mark an essential step for the development of nanocarbon-based cathodes, as we specifically evaluate the electrode performance under real fuel cell conditions...
October 21, 2016: Nanotechnology
Jingyi Zhu, Tilo Mathes, Yusaku Hontani, Maxime T A Alexandre, Kee Chua Toh, Peter Hegemann, John T M Kennis
The two Light, Oxygen, and Voltage domains of phototropin are blue-light photoreceptor domains which control various functions in plants and green algae. The key step of the light-driven reaction is the formation of a photoadduct between its FMN chromophore and a conserved cysteine, where the canonical reaction proceeds through the FMN triplet state. Here, complete photoreaction mapping of CrLOV2 from Chlamydomonas reinhardtii phototropin and AsLOV2 from Avena sativa phototropin-1 was realized by ultrafast broadband spectroscopy from femtoseconds to microseconds...
October 21, 2016: Journal of Physical Chemistry Letters
Qihui Chen
A temperature and anions induced coordination-driven self-assembly system based on dynamic Ag6L4 metallocage has been developed. Induced by SbF6- anions, both of kinetic-control [Ag3L2(SbF6)3]n and thermodynamic-control [Ag2L2(SbF6)2]n can be reassembled from discrete Ag6L4(SbF6)6 metallocages at 30 ℃, raising temperature up to 40 ℃ results to selective inhibition of their kinetic product. While driven by BF4- anions, dynamic Ag6L4(BF4)6 metallocages prior to self-assemble into thermodynamic-control polycage at 25 ℃, lowing the temperature down to 0℃ leads to selective inhibition of their thermodynamic product...
October 20, 2016: Chemistry: a European Journal
Nicole Cathcart, Neil Coombs, Ilya Gourevich, Vladimir Kitaev
In this work, we use silver decahedral nanoparticle (AgDeNP) seeds to synthesize pentagonal silver stars (AgStDeNPs) and study the sensing properties of these nanoparticles. The regrowth process of AgStDeNPs is kinetically-controlled, so the purity of the seed NPs is critical to avoid secondary deposition in the highly non-equilibrium reduction. To control the regrowth process, surface blocking with sodium polyacrylate (PANa) was implemented. PANa moderates rough silver nanostructures typically obtained by reduction with ascorbic acid...
October 21, 2016: Nanoscale
Laleh Majari Kasmaee, Asghar Aryanfar, Zarui Chikneyan, Michael R Hoffmann, Agustín J Colussi
Understanding the mechanism of formation of solid-electrolyte interphases (SEI) is key to the prospects of lithium metal batteries (LMB). Here, we investigate via cyclic voltammetry, impedance spectroscopy and chronoamperometry the role of kinetics in controlling the properties of the SEI generated from the reduction of propylene carbonate (PC, a typical solvent in LMB). Our observations are consistent with the operation of a radical chain PC electropolymerization into polymer units whose complexity increases at lower initiation rates...
September 16, 2016: Chemical Physics Letters
Andreas Hahn, Martin Schain, Maria Erlandsson, Petter Sjölin, Gregory M James, Olof T Strandberg, Douglas Hägerström, Rupert Lanzenberger, Jonas Jögi, Tomas G Olsson, Ruben Smith, Oskar Hansson
: Aggregation of hyperphosphorylated tau is a major hallmark of many neurodegenerative diseases, including Alzheimer's disease. In vivo imaging with positron emission tomography (PET) may offer important insights in pathophysiological mechanisms, diagnosis and disease progression. We describe different strategies for quantification of (18)F-AV1451 (T807) tau binding, including models with blood sampling and non-invasive alternatives. METHODS: 15 subjects (4 controls, 6 Alzheimer's disease (AD), 3 progressive supranuclear palsy (PSP), 2 cortico basal syndrome (CBS)) underwent 180 min PET with (18)F-AV1451 and arterial blood sampling...
October 20, 2016: Journal of Nuclear Medicine: Official Publication, Society of Nuclear Medicine
Victor M Niemeijer, Ruud F Spee, Thijs Schoots, Pieter F F Wijn, Hareld M Kemps
The extent and speed of transient skeletal muscle deoxygenation during exercise onset in chronic heart failure (CHF) patients is related to impairments of local O2 delivery and utilization. This study examined the physiological background of submaximal exercise performance in 19 moderately impaired CHF patients (Weber class A, B, and C) compared with 19 matched healthy control (HC) subjects by measuring skeletal muscle oxygenation (SmO2) changes during cycling exercise. All subjects performed two subsequent moderate-intensity 6-minute exercise tests (bout 1 and 2) with measurements of pulmonary oxygen uptake kinetics, and SmO2 using near infrared (NIR) spatially resolved spectroscopy (SRS) at the vastus lateralis for determination of absolute oxygenation values, amplitudes, kinetics (mean response time for onset), and deoxygenation overshoot characteristics...
October 7, 2016: American Journal of Physiology. Heart and Circulatory Physiology
Jiayu Ma, Yanfang Zhang, Yuanhang Qin, Zaikun Wu, Tielin Wang, Cunwen Wang
The leaching kinetics of K-feldspar in H2SO4-CaF2 system with the assistant of ultrasound was investigated. The effects of various factors, such as sulfuric acid concentration, liquid-to-solid ratio, CaF2 dosage and leaching temperature were comprehensively studied. The dissolution fraction of potassium can reach more than 83% under the optimum operation conditions with ultrasound. Because of the cavitation effect, the intensified effect with ultrasound has more obvious at lower temperature than higher temperature...
October 12, 2016: Ultrasonics Sonochemistry
Mozhgan Akbari Alavijeh, Mehdi Nasiri Sarvi, Zahra Ramazani Afarani
In this study properties of adsorption of vitamin B12 onto nanoclay were investigated. Results of kinetics of adsorption were used to investigate the structural formation and nature of interaction of vitamin B12 onto montmorillonite as a carrier. The results showed that at the early stages of adsorption with migration of interlayer cations of montmorillonite (Ca(2+)and Na(+)) to the edges a cationic bridge was formed and the vitamin biomolecules were adsorbed at the edges of montmorillonite. By increasing the adsorption duration, vitamin B12 molecules gradually diffused in between montmorillonite layers...
March 15, 2017: Food Chemistry
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