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https://www.readbyqxmd.com/read/29451786/the-catalytic-reaction-of-nitroxides-with-peroxyl-radicals-and-its-relevance-to-their-cytoprotective-properties
#1
Markus Griesser, Ron Shah, Antonius T Van Kessel, Omkar Zilka, Evan A Haidasz, Derek A Pratt
Sterically-hindered nitroxides such as 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) have long been ascribed antioxidant activity that is thought to underlie their chemopreventive and anti-aging properties. However, the most commonly invoked reactions in this context - combination with an alkyl radical to give a redox inactive alkoxyamine or the catalysis of superoxide dismutation - are unlikely to be relevant under (most) physiological conditions. Herein we characterize the kinetics and mechanisms of the reactions of TEMPO, as well as an N-arylnitroxide and a N,N-diarylnitroxide, with alkylperoxyl radicals, the propagating species in lipid peroxidation...
February 16, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29406617/electrochemical-water-oxidation-and-stereoselective-oxygen-atom-transfer-mediated-by-a-copper-complex
#2
Maria-Chrysanthi Kafentzi, Raffaello Papadakis, Federica Gennarini, Amélie Kochem, Olga Iranzo, Yves Le Mest, Nicolas Le Poul, Thierry Tron, Bruno Faure, A Jalila Simaan, Marius Réglier
Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf)2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used...
February 6, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29383866/light-driven-water-splitting-mediated-by-photogenerated-bromine
#3
Matthew Vincent Sheridan, Ying Wang, Degao Wang, Ludovic Troian-Gautier, Christopher J Dares, Benjamin D Sherman, Thomas J Meyer
Light-driven water splitting was achieved using a dye-sensitized mesoporous oxide film and the oxidation of bromide (Br-) to bromine (Br2) or tribromide (Br3-). The chemical oxidant (Br2 or Br3-) is formed during illumination at the photoanode and used as a sacrificial oxidant to drive a water oxidation catalyst (WOC), here demonstrated using [Ru(bda)(pic)2], (1, pic = picoline, bda = 2,2'-bipyridine-6,6'-dicarboxylate). The photochemical oxidation of bromide produces a chemical oxidant with a potential of 1...
January 31, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29359551/degradable-nir-ptt-nanoagents-with-a-potential-cu-cu2o-polymer-structure
#4
Yu-Wei Tai, Yi-Chun Chiu, Po-Ting Wu, Jiashing Yu, Yu-Cheng Chin, Shu-Pao Wu, Yu-Chun Chuang, Ho-Chen Hsieh, Ping-Shan Lai, Hsiu-Ping Yu, Mei-Yi Liao
Cu@Cu2O@PSMA polymer nanoparticles (Cu@Cu2O@polymer NPs) with near-infrared (NIR) absorption were successfully synthesized in a single-step oxidation reaction of Cu@PSMA polymer NPs at 100 °C for 20 min. The shape, structure, and optical properties of the Cu@Cu2O@polymer NPs were tailorable by controlling the reaction parameters, e.g., using the initial Cu@PSMA polymer NP as a template and varying the halide ion content, heating temperature, and reaction time. The Cu@Cu2O@polymer NPs exhibited robust NIR absorption between 650 nm and 710 nm and possessed superior oxidation resistance in water and culture media...
January 23, 2018: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/29334114/sensing-local-ph-and-ion-concentration-at-graphene-electrode-surfaces-using-in-situ-raman-spectroscopy
#5
Haotian Shi, Nirakar Poudel, Bingya Hou, Lang Shen, Jihan Chen, Alexander V Benderskii, Stephen B Cronin
We report a novel approach to probe the local ion concentration at graphene/water interfaces using in situ Raman spectroscopy. Here, the upshifts observed in the G band Raman mode under applied electrochemical potentials are used to determine the charge density in the graphene sheet. For voltages up to ±0.8 V vs. NHE, we observe substantial upshifts in the G band Raman mode by as much as 19 cm-1, which corresponds to electron and hole carrier densities of 1.4 × 1013 cm-2 and Fermi energy shifts of ±430 meV...
January 15, 2018: Nanoscale
https://www.readbyqxmd.com/read/29329026/the-interaction-of-pyridoxal-isonicotinoyl-hydrazone-pih-and-salicylaldehyde-isonicotinoyl-hydrazone-sih-with-iron
#6
Yu-Lin Chen, Xiaole Kong, Yuanyuan Xie, Robert C Hider
The interaction of pyridoxal isonicotinoyl hydrazone (PIH) and salicylaldehyde isonicotinoyl hydrazone (SIH), two important biologically active chelators, with iron has been investigated by spectrophotometric methods. High iron(III) affinity constants were determined for PIH, logβ2=37.0 and SIH, logβ2=37.6. The associated redox potentials of the iron complexes were determined using cyclic voltammetry at pH7.4 as +130mV (vs normal hydrogen electrode, NHE) for PIH and +136mV(vs NHE) for SIH. These redox potentials are much higher than those corresponding to iron chelators in clinical use, namely deferiprone, -620mV; desferasirox, -600mV and desferrioxamine, -468mV...
December 21, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/29305650/a-look-at-the-smelly-side-of-physiology-transport-of-short-chain-fatty-acids
#7
REVIEW
Friederike Stumpff
Fermentative organs such as the caecum, the colon, and the rumen have evolved to produce and absorb energy rich short chain fatty acids (SCFA) from otherwise indigestible substrates. Classical models postulate diffusional uptake of the undissociated acid (HSCFA). However, in net terms, a major part of SCFA absorption occurs with uptake of Na+ and resembles classical, coupled electroneutral NaCl transport. Considerable evidence suggests that the anion transporting proteins expressed by epithelia of fermentative organs are poorly selective and that their main function may be to transport acetate-, propionate-, butyrate- and HCO3- as the physiologically relevant anions...
January 6, 2018: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/29295495/rethinking-the-combination-of-proton-exchanger-inhibitors-in-cancer-therapy
#8
REVIEW
Elisabetta Iessi, Mariantonia Logozzi, Davide Mizzoni, Rossella Di Raimo, Claudiu T Supuran, Stefano Fais
Microenvironmental acidity is becoming a key target for the new age of cancer treatment. In fact, while cancer is characterized by genetic heterogeneity, extracellular acidity is a common phenotype of almost all cancers. To survive and proliferate under acidic conditions, tumor cells up-regulate proton exchangers and transporters (mainly V-ATPase, Na⁺/H⁺ exchanger (NHE), monocarboxylate transporters (MCTs), and carbonic anhydrases (CAs)), that actively extrude excess protons, avoiding intracellular accumulation of toxic molecules, thus becoming a sort of survival option with many similarities compared with unicellular microorganisms...
December 23, 2017: Metabolites
https://www.readbyqxmd.com/read/29288770/the-3-end-region-of-the-human-pdgfr-%C3%AE-core-promoter-nuclease-hypersensitive-element-forms-a-mixture-of-two-unique-end-insertion-g-quadruplexes
#9
Buket Onel, Megan Carver, Prashansa Agrawal, Laurence H Hurley, Danzhou Yang
BACKGROUND: While the most stable G-quadruplex formed in the human PDGFR-β promoter nuclease hypersensitive element (NHE) is the 5'-mid G-quadruplex, the 3'-end sequence that contains a 3'-GGA run forms a less stable G-quadruplex. Recently, the 3'-end G-quadruplex was found to be a transcriptional repressor and can be selectively targeted by a small molecule for PDGFR-β downregulation. METHOD: We use 1D and 2D high-field NMR, in combination with Dimethylsulfate Footprinting, Circular Dichroism Spectroscopy, and Electrophoretic Mobility Shift Assay...
December 27, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/29279188/clinical-correlates-of-negative-health-events-in-a-research-sample-with-epilepsy
#10
Neha Kumar, Kari Colon-Zimmermann, Edna Fuentes-Casiano, Hongyan Liu, Curtis Tatsuoka, Kristin A Cassidy, Mustafa Kahriman, Peijun Chen, Martha Sajatovic
AIMS: In spite of advances in care, people with epilepsy experience negative health events (NHEs), such as seizures, emergency department (ED) visits, and hospitalizations. Being able to identify characteristics that are associated with NHE risk can help inform care approaches that reduce complications and burden. This analysis using baseline data from a larger randomized epilepsy self-management clinical trial assessed the relationship between demographic and clinical variables vs. seizure-related complications among people with epilepsy...
December 23, 2017: Epilepsy & Behavior: E&B
https://www.readbyqxmd.com/read/29229646/nhe-and-diffusion-dependent-proton-fluxes-across-the-tubular-system-membranes-of-fast-twitch-muscle-fibers-of-the-rat
#11
Bradley S Launikonis, Tanya R Cully, Laszlo Csernoch, D George Stephenson
The complex membrane structure of the tubular system (t-system) in skeletal muscle fibers is open to the extracellular environment, which prevents measurements of H+ movement across its interface with the cytoplasm by conventional methods. Consequently, little is known about the t-system's role in the regulation of cytoplasmic pH, which is different from extracellular pH. Here we describe a novel approach to measure H+-flux measurements across the t-system of fast-twitch fibers under different conditions. The approach involves loading the t-system of intact rat fast-twitch fibers with a strong pH buffer (20 mM HEPES) and pH-sensitive fluorescent probe (10 mM HPTS) before the t-system is sealed off...
December 11, 2017: Journal of General Physiology
https://www.readbyqxmd.com/read/29227582/role-of-the-sodium-hydrogen-exchanger-in-mediating-the-renal-effects-of-drugs-commonly-used-in-the-treatment-of-type-2-diabetes
#12
REVIEW
Milton Packer
Diabetes is characterized by an increased activity of the sodium-hydrogen exchanger (NHE) in the glomerulus and renal tubules, which contributes importantly to the development of nephropathy. Despite the established role played by the exchanger in experimental studies, it has not been specifically targeted by those seeking to develop novel pharmacological treatments for diabetes. This review demonstrates that many existing drugs that are commonly prescribed to patients with diabetes act on the NHE1 and NHE3 isoforms in the kidney...
December 11, 2017: Diabetes, Obesity & Metabolism
https://www.readbyqxmd.com/read/29219306/the-key-ruv-o-intermediate-of-site-isolated-mononuclear-water-oxidation-catalyst-detected-by-in-situ-x-ray-absorption-spectroscopy
#13
Dmitry Lebedev, Yuliana Pineda-Galvan, Yuki Tokimaru, Alexey Fedorov, Nicolas Kaeffer, Christophe Copéret, Yulia Pushkar
Improvement of the oxygen evolution reaction (OER) is a challenging step towards the development of sustainable energy technologies. Enhancing the OER rate and efficiency relies on understanding the water oxidation mechanism, which entails the characterization of the reaction intermediates. Very active Ru-bda type (bda is 2,2'-bipyridine-6,6'-dicarboxylate) molecular OER catalysts are proposed to operate via a transient 7-coordinate RuV=O intermediate, which so far has never been detected due to its high reactivity...
December 8, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29219228/structure-and-function-of-yeast-and-fungal-na-h-antiporters
#14
REVIEW
Debajyoti Dutta, Larry Fliegel
Sodium proton antiporters (or sodium proton exchangers [NHEs]) are a critical family of membrane proteins that exchange sodium for protons across cell membranes. In yeast and plants, their primary function is to keep the sodium concentration low inside the cytoplasm. One class of NHE constitutively expressed in yeast is the plasma membrane Na+ /H+ antiporter, and another class is expressed on the endosomal/vacuolar membrane. At present, four bacterial plasma membrane antiporter structures are known and nuclear magnetic resonance structures are available for the membrane spanning transmembrane helices of mammalian and yeast NHEs...
December 8, 2017: IUBMB Life
https://www.readbyqxmd.com/read/29218398/enhanced-hemoglobin-oxygen-unloading-in-migratory-salmonids
#15
Jacelyn J Shu, Till S Harter, Phillip R Morrison, Colin J Brauner
Recent findings indicate that some teleost fishes may be able to greatly enhance hemoglobin-oxygen (Hb-O2) unloading at the tissues under conditions that result in catecholamine release. The putative mechanism relies on the high pH sensitivity of teleost hemoglobin (Hb), intracellular red blood cell (RBC) pH regulation via β-adrenergic Na+/H+ exchanger (β-NHE) activity, and plasma-accessible carbonic anhydrase at the tissues that short-circuits RBC pH regulation. Previous studies have shown that in rainbow trout, this system may double Hb-O2 unloading to red muscle compared to a situation without short-circuiting...
December 7, 2017: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology
https://www.readbyqxmd.com/read/29212874/the-na-k-h-exchanger-nhx1-controls-multivesicular-body-vacuolar-lysosome-fusion
#16
Mahmoud Abdul Karim, Christopher Leonard Brett
Loss-of-function mutations in human endosomal Na+(K+)/H+ Exchangers (NHEs) NHE6 and NHE9 are implicated in neurological disorders including Christianson Syndrome, autism and attention deficit and hyperactivity disorder (ADHD). These mutations disrupt retention of surface receptors within neurons and glial cells by affecting their delivery to lysosomes for degradation. However, the molecular basis of how these endosomal NHEs control endocytic trafficking is unclear. Using Saccharomyces cerevisiae as a model, we conducted cell-free organelle fusion assays to show that transport activity of the orthologous endosomal NHE Nhx1 is important for multivesicular body (MVB)-vacuolar lysosome fusion, the last step of endocytosis required for surface protein degradation...
December 6, 2017: Molecular Biology of the Cell
https://www.readbyqxmd.com/read/29209224/na-h-exchanger-3-is-expressed-in-two-distinct-types-of-ionocyte-and-probably-augments-ammonia-excretion-in-one-of-them-in-the-gills-of-the-climbing-perch-exposed-to-seawater
#17
Xiu L Chen, Biyan Zhang, You R Chng, Jasmine L Y Ong, Shit F Chew, Wai P Wong, Siew H Lam, Yuen K Ip
The freshwater climbing perch, Anabas testudineus, is an euryhaline teleost and an obligate air-breather with the ability to actively excrete ammonia. Members of the Na+/H+ exchanger (NHE) family help maintain intracellular pH homeostasis and ionic balance through the electroneutral exchange of Na+ and H+. This study aimed to obtain, from the gills of A. testudineus, the full cDNA coding sequence of nhe3, and to determine the effects of exposure to seawater or 100 mmol l-1 of NH4Cl in fresh water on its mRNA and protein expression levels...
2017: Frontiers in Physiology
https://www.readbyqxmd.com/read/29201052/rapid-action-of-aldosterone-on-protein-levels-of-sodium-hydrogen-exchangers-and-protein-kinase-c-beta-isoforms-in-rat-kidney
#18
Somchit Eiam-Ong, Mookda Chaipipat, Krissanapong Manotham, Somchai Eiam-Ong
Previous in vitro studies demonstrated that aldosterone rapidly activates sodium-hydrogen exchangers 1 and 3 (NHE 1 and 3). In vitro investigations revealed that protein kinase C (PKC) regulates NHE properties. We previously demonstrated that aldosterone rapidly enhances PKCα protein abundance in the rat kidney. There are no reports of renal PKCβ (I and II) protein levels related to the regulation by aldosterone. There are also no in vivo data regarding the rapid effects of aldosterone on renal protein levels of NHE (1 and 3) and PKCβ (I and II), simultaneously...
2017: International Journal of Endocrinology
https://www.readbyqxmd.com/read/29197997/class-effects-of-sglt2-inhibitors-in-mouse-cardiomyocytes-and-hearts-inhibition-of-na-h-exchanger-lowering-of-cytosolic-na-and-vasodilation
#19
Laween Uthman, Antonius Baartscheer, Boris Bleijlevens, Cees A Schumacher, Jan W T Fiolet, Anneke Koeman, Milena Jancev, Markus W Hollmann, Nina C Weber, Ruben Coronel, Coert J Zuurbier
AIMS/HYPOTHESIS: Sodium-glucose cotransporter 2 (SGLT2) inhibitors (SGLT2i) constitute a novel class of glucose-lowering (type 2) kidney-targeted agents. We recently reported that the SGLT2i empagliflozin (EMPA) reduced cardiac cytosolic Na+ ([Na+]c) and cytosolic Ca2+ ([Ca2+]c) concentrations through inhibition of Na+/H+ exchanger (NHE). Here, we examine (1) whether the SGLT2i dapagliflozin (DAPA) and canagliflozin (CANA) also inhibit NHE and reduce [Na+]c; (2) a structural model for the interaction of SGLT2i to NHE; (3) to what extent SGLT2i affect the haemodynamic and metabolic performance of isolated hearts of healthy mice...
December 2, 2017: Diabetologia
https://www.readbyqxmd.com/read/29192837/effects-of-the-nordic-hamstring-exercise-on-sprint-capacity-in-male-football-players-a-randomized-controlled-trial
#20
Lasse Ishøi, Per Hölmich, Per Aagaard, Kristian Thorborg, Thomas Bandholm, Andreas Serner
This assessor-blinded, randomized controlled superiority trial investigated the efficacy of the 10-week Nordic Hamstring exercise (NHE) protocol on sprint performance in football players. Thirty-five amateur male players (age: 17-26 years) were randomized to a do-as-usual control group (CG; n = 17) or to 10-weeks of supervised strength training using the NHE in-season (IG; n = 18). A repeated-sprint test, consisting of 4 × 6 10 m sprints, with 15 s recovery period between sprints and 180 s between sets, was conducted to evaluate total sprint time as the primary outcome...
December 1, 2017: Journal of Sports Sciences
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