228 research outputs found
Development of an Organoautocatalyzed Double σ‐Bond C(sp2)‐N Transamination Metathesis Reaction
No full textThe transamination reaction, which involves the conversion of one amine to another, traditionally relies on biological enzyme catalysts. Although chemists have recently developed a few transition metal‐catalyzed methods, mimicking these enzymes to interconvert amine groups in acyclic substrates via transamination metathesis of a single C(sp 2 )─N bond, transamination of cyclic tertiary amines has remained a challenge in synthetic chemistry. Here, we present the development of organoautocatalyzed transamination metathesis of two C(sp 2 )─N bonds in a cyclic substrate that allows for the challenging transformation to take place with up to 95% yield under exceptionally mild reaction conditions at room temperature without external catalysts and/or additives. The reaction mechanism has been studied in detail through time‐resolved 1 H‐NMR, 2D NMR, and computational methods. Remarkably, in situ‐formed pyrrolidinium salt acts as a hydrogen bond donor (HBD) organoautocatalyst in this multi‐step domino process. The new organoautocatalyzed methodology gives environmentally friendly, atom‐economical, straightforward, and rapid access to N ‐substituted 3,5‐dinitro‐1,4‐dihydropyridines (DNDHPs), thus offering facile entry to privileged bioactive compounds.Organoautocatalyzed transamination metathesis of cyclic tertiary amines is disclosed as a high‐yielding, scalable reaction that proceeds under mild, catalyst‐free conditions. It operates via a multi‐step domino reaction mechanism, where an in situ‐formed pyrrolidinium salt functions as a HBD organoautocatalyst. The reaction opens the door for the efficient synthesis of novel N‐substituted DNDHPs of interest in both life and materials sciences. imageDeutsche Forschungsgemeinschaft 10.13039/501100001659Volkswagen Foundation 10.13039/501100001663Swedish Research Council 10.13039/50110000435
Electro optical tuning of Tamm-plasmon exciton-polaritons
No full textThis work was financially supported by the state of Bavaria, the bilateral project of the Deutsche Forschungsgemeinschaft (within the project LIEPOLATE) and the Polish Ministry of Science and higher education (Project No. DPN/N99/DFG/2010) and the EU within the project SPANGL4Q.We report on electro optical tuning of the emission from GaAs quantum wells resonantly coupled to a Tamm-plasmon mode in a hybrid metal/dielectric structure. The structures were studied via momentum resolved photoluminescence and photoreflectance spectroscopy, and the surface metal layer was used as a top gate, which allowed for a precise tuning of the quantum well emission via the quantum confined Stark effect. By tuning the resonance, we were able to observe the characteristic anticrossing behavior of a polaritonic emission in the strong light-matter coupling regime, yielding a Rabi splitting of (9.2 ± 0.2) meV.Peer reviewe
ActRIIB blockade increases force-generating capacity and preserves energy supply in exercising mdx mouse muscle in vivo
No full textInternational audiencePostnatal blockade of the activin type IIB receptor (ActRIIB) represents a promising therapeutic strategy for counteracting dystrophic muscle wasting. However, its impact on muscle function and bioenergetics remains poorly documented in physiologic conditions. We have investigated totally noninvasively the effect of 8-wk administration of either soluble ActRIIB signaling inhibitor (sActRIIB-Fc) or vehicle PBS (control) on gastrocnemius muscle force-generating capacity, energy metabolism, and anatomy in dystrophic mdx mice using magnetic resonance (MR) imaging and dynamic [(31)P]-MR spectroscopy ([(31)P]-MRS) in vivo ActRIIB inhibition increased muscle volume (+33%) without changing fiber-type distribution, and increased basal animal oxygen consumption (+22%) and energy expenditure (+23%). During an in vivo standardized fatiguing exercise, maximum and total absolute contractile forces were larger (+40 and 24%, respectively) in sActRIIB-Fc treated animals, whereas specific force-generating capacity and fatigue resistance remained unaffected. Furthermore, sActRIIB-Fc administration did not alter metabolic fluxes, ATP homeostasis, or contractile efficiency during the fatiguing bout of exercise, although it dramatically reduced the intrinsic mitochondrial capacity for producing ATP. Overall, sActRIIB-Fc treatment increased muscle mass and strength without altering the fundamental weakness characteristic of dystrophic mdx muscle. These data support the clinical interest of ActRIIB blockade for reversing dystrophic muscle wasting.-Béchir, N., Pecchi, E., Vilmen, C., Le Fur, Y., Amthor, H., Bernard, M., Bendahan, D., Giannesini, B. ActRIIB blockade increases force-generating capacity and preserves energy supply in exercising mdx mouse muscle in vivo
Robust Molecular Anodes for Electrocatalytic Water Oxidation Based on Electropolymerized Molecular Cu Complexes
No full textA multistep synthesis of a new tetra-amidate macrocyclic ligand functionalized with alkyl-thiophene moieties, 15,15-bis(6-(thiophen-3-yl)hexyl)-8,13-dihydro-5H-dibenzo[b,h][1,4,7,10]tetraazacyclotridecine-6,7,14,16(15H,17H)-tetraone, H4L, is reported. The reaction of the deprotonated ligand, L4−, and Cu(II) generates the complex [LCu]2−, that can be further oxidized to Cu(III) with iodine to generate [LCu]−. The H4L ligand and their Cu complexes have been thoroughly characterized by analytic and spectroscopic techniques (including X-ray Absorption Spectroscopy, XAS). Under oxidative conditions, the thiophene group of [LCu]2− complex polymerizes on the surface of graphitic electrodes (glassy carbon disks (GC), glassy carbon plates (GCp), carbon nanotubes (CNT), or graphite felts (GF)) generating highly stable thin films. With CNTs deposited on a GC by drop casting, hybrid molecular materials labeled as GC/CNT@p-[LCu]2− are obtained. The latter are characterized by electrochemical techniques that show their capacity to electrocatalytically oxidize water to dioxygen at neutral pH. These new molecular anodes achieve current densities in the range of 0.4 mA cm−2 at 1.30 V versus NHE with an onset overpotential at ≈250 mV. Bulk electrolysis experiments show an excellent stability achieving TONs in the range of 7600 during 24 h with no apparent loss of catalytic activity and maintaining the molecular catalyst integrity, as evidenced by electrochemical techniques and XAS spectroscopy
Exercise training attenuates the hypermuscular phenotype and restores skeletal muscle function in the myostatin null mouse
No full textMyostatin regulates both muscle mass and muscle metabolism. The myostatin null (MSTN-/-) mouse has a hypermuscular phenotype owing to both hypertrophy and hyperplasia of the myofibres. The enlarged muscles display a reliance on glycolysis for energy production; however, enlarged muscles that develop in the absence of myostatin have compromised force-generating capacity. Recent evidence has suggested that endurance exercise training increases the oxidative properties of muscle. Here, we aimed to identify key changes in the muscle phenotype of MSTN-/- mice that can be induced by training. To this end, we subjected MSTN-/- mice to two different forms of training, namely voluntary wheel running and swimming, and compared the response at the morphological, myocellular and molecular levels. We found that both regimes normalized changes of myostatin deficiency and restored muscle function. We showed that both exercise training regimes increased muscle capillary density and the expression of Ucp3, Cpt1a, Pdk4 and Err?, key markers for oxidative metabolism. Cross-sectional area of hypertrophic myofibres from MSTN-/- mice decreased towards wild-type values in response to exercise and, in this context, Bnip3, a key autophagy-related gene, was upregulated. This reduction in myofibre size caused an increase of the nuclear-to-cytoplasmic ratio towards wild-type values. Importantly, both training regimes increased muscle force in MSTN-/- mice. We conclude that impaired skeletal muscle function in myostatin-deficient mice can be improved through endurance exercise-mediated remodelling of muscle fibre size and metabolic profil
[Recueil. Portraits de C. H. Amthor (XVIIe-XVIIIe s.)]
No full textAppartient à l’ensemble documentaire : IconEST
Effect Of Michigan Funded Chapter 3 Program Upon Attainment Of Reading And Mathematics Performance Objectives By Kindergarten Children In A Michigan School District.
No full textPhDSchool administrationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/190123/2/7804636.pd
An experimental comparison of three methods for presenting selected concepts of descriptive geometry
No full textThe function of Myostatin and strategies of Myostatin blockade - new hope for therapies aimed at promoting growth of skeletal muscle
No full textThe function of Myostatin and strategies of Myostatin blockade - new hope for therapies aimed at promoting growth of skeletal muscle
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