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40 results on '"Schauer, Phil A."'

5. Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease

Author

Wang, Zeneng, Klipfell, Elizabeth, Bennett, Brian J., Koeth, Robert, Levison, Bruce S., DuGar, Brandon, Feldstein, Ariel E., Britt, Earl B., Fu, Xiaoming, Chung, Yoon-Mi, Wu, Yuping, Schauer, Phil, Smith, Jonathan D., Allayee, Hooman, Tang, W.H. Wilson, DiDonato, Joseph A., Lusis, Aldons J., and Hazen, Stanley L.

Subjects
Metabolism -- Research -- Health aspects -- Physiological aspects, Microbiota (Symbiotic organisms) -- Health aspects -- Research -- Physiological aspects, Lecithin -- Physiological aspects -- Research -- Health aspects, Cardiovascular diseases -- Risk factors -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Metabolomics studies hold promise for the discovery of pathways linked to disease processes. Cardiovascular disease (CVD) represents the leading cause of death and morbidity worldwide. Here we used a metabolomics approach to generate unbiased small-molecule metabolic profiles in plasma that predict risk for CVD. Three metabolites of the dietary lipid phosphatidylcholine-choline, trimethylamine N-oxide (TMAO) and betaine-were identified and then shown to predict risk for CVD in an independent large clinical cohort. Dietary supplementation of mice with choline, TMAO or betaine promoted upregulation of multiple macrophage scavenger receptors linked to atherosclerosis, and supplementation with cholineorTMAO promoted atherosclerosis. Studies using germ- free mice confirmedacritical role for dietary choline and gut flora in TMAO production, augmented macrophage cholesterol accumulation and foam cell formation. Suppression of intestinal microflora in atherosclerosis-prone mice inhibited dietary-choline-enhanced atherosclerosis. Genetic variations controlling expression of flavin monooxygenases, an enzymatic source of TMAO, segregated with atherosclerosis in hyperlipidaemic mice. Discovery of a relationship between gut-flora-dependent metabolism of dietary phosphatidylcholine and CVD pathogenesis provides opportunities for the development of new diagnostic tests and therapeutic approaches for atherosclerotic heart disease., The pathogenesis of CVD includes genetic and environmental factors. A known environmental risk factor for the development of CVD is a diet rich in lipids. A relationship between blood cholesterol [...]

Published
2011
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9. Kinetics teach that electronic coupling lowers the free-energy change that accompanies electron transfer

Author

UCL - SST/IMCN/MOST - Molecular Chemistry, Materials and Catalysis, Sampaio, Renato N., Piechota, Eric J., Troian-Gautier, Ludovic, Maurer, Andrew B., Hu, Ke, Schauer, Phil A., Blair, Amber D., Berlinguette, Curtis P., Meyer, Gerald J., UCL - SST/IMCN/MOST - Molecular Chemistry, Materials and Catalysis, Sampaio, Renato N., Piechota, Eric J., Troian-Gautier, Ludovic, Maurer, Andrew B., Hu, Ke, Schauer, Phil A., Blair, Amber D., Berlinguette, Curtis P., and Meyer, Gerald J.

Abstract

Electron-transfer theories predict that an increase in the quantum-mechanical mixing (HDA) of electron donor and acceptor wavefunctions at the instant of electron transfer drives equilibrium constants toward unity. Kinetic and equilibrium studies of four acceptor–bridge–donor (A-B-D) compounds reported herein provide experimental validation of this prediction. The compounds have two redox-active groups that differ only by the orientation of the aromatic bridge: a phenyl–thiophene bridge (p) that supports strong electronic coupling of HDA > 1,000 cm−1; and a xylyl–thiophene bridge (x) that prevents planarization and decreases HDA < 100 cm−1 without a significant change in distance. Pulsed-light excitation allowed kinetic determination of the equilibrium constant, Keq. In agreement with theory, Keq(p) were closer to unity compared to Keq(x). A van’t Hoff analysis provided clear evidence of an adiabatic electron-transfer pathway for p-series and a nonadiabatic pathway for x-series. Collectively, the data show that the absolute magnitude of the thermodynamic driving force for electron transfers are decreased when adiabatic pathways are operative, a finding that should be taken into account in the design of hybrid materials for solar energy conversion.

Published
2018

11. Straightforward Access to Tetrametallic Complexes with a Square Array by Oxidative Dimerization of Organometallic Wires

Author

Burgun, Alexandre, Gendron, Frédéric, Schauer, Phil A., Skelton, Brian W., Low, Paul J., Costuas, Karine, Halet, Jean-François, Bruce, Michael I., and Lapinte, Claude

Abstract

The bimetallic ruthenium complex {Cp(dppe)Ru}2(μ-CCCCCC) (3; Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane) has been prepared and the molecular structure determined. The cyclic voltammogram of 3is characterized by three reversible one-electron events with a large potential difference between the two first waves (ΔE° = 0.44 V), indicating the large thermodynamic stability of the MV (mixed-valence) 3(PF6), which can be considered as a class III MV complex. The complex 3(PF6) was quantitatively prepared by treatment of 3with 1 equiv of [FeCp2](PF6) at −78 °C and characterized by EPR spectroscopy. Above −10 °C, solutions of 3(PF6) provide the asymmetric tetranuclear complex {cyclo-C([Ru])C(CCCC[Ru])C(CC[Ru])C(CC[Ru])}(PF6)2(4(PF6)2; [Ru] = Cp(dppe)Ru) which was formed regiospecifically and isolated in 92% yield. Thus, despite the thermodynamic stability of the monocation radical 3(PF6) as evidenced by the electrochemical data, and the extensively delocalized electronic structure, a slow dimerization reaction takes place, affording a stable, tetranuclear complex. The new compound was characterized by a single-crystal X-ray diffraction study, cyclic voltammetry, and multinuclear NMR, IR, UV–vis, and near-IR spectroscopy, and the data were analyzed with the support of quantum chemical investigations at the DFT level of theory. The regiospecificity of the dimerization reaction is controlled by a balance of steric and electronic factors, which favors intermolecular (Cα+ Cγ) radical coupling.

Published
2024
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28. Coordinating Tectons: Bipyridyl Terminated Allenylidene Complexes

Author

Cifuentes, Marie P., primary, Humphrey, Mark G., additional, Koutsantonis, George A., additional, Lengkeek, Nigel A., additional, Petrie, Simon, additional, Sanford, Vanessa, additional, Schauer, Phil A., additional, Skelton, Brian W., additional, Stranger, Robert, additional, and White, Allan H., additional

Published
2008
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33. Stabilization of Ruthenium Sensitizers to Ti02 Surfaces through Cooperative Anchoring Groups.

Author

Brown, Douglas G., Schauer, Phil A., Borau-Garcia, Javier, Fancy, Brandon R., and Berlinguette, Curtis P.

Subjects
*RUTHENIUM, *COOPERATIVE binding (Biochemistry), *PHOTOSENSITIZERS, *ELECTROCATALYSIS kinetics, *DYE-sensitized solar cells
Abstract

Cooperative binding of a bis(tridentate) ruthenium(I1) complex to a Ti02 surface through carboxylate and phosphonate groups is demonstrated to be an effective method for achieving a robust anchoring motif in aqueous media while maintaining charge transfer from the dye into the semiconductor. The realization of these complementary goals has broad implications for solar cells and (photo)electrocatalytic schemes. [ABSTRACT FROM AUTHOR]

Published
2013
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37. Guest Perspective.

Author

SCHAUER, PHIL

Subjects
*MEDICAL personnel, *ARTIFICIAL respiration equipment, *BARIATRIC surgery, *GASTRIC bypass, *GLUCAGON-like peptide 1, *HYPOVENTILATION, *MEDICAL societies, *HEART assist devices
Published
2021

39. Synthesis and Properties of Ferrocenyl Allenylidene Complexes: X-ray Structure of [Ru(CCCHFc)(PPh3)2(η5-C5H5)][PF6]·CH2Cl2.

Author

Byrne, Lindsay T., Koutsantonis, George A., Sanford, Vanessa, Selegue, John P., Schauer, Phil A., and Iyer, Ramnath S.

Abstract

Reactions of the transition metal halide complexes [MXL2(Cp)] (M = Fe, X = I, L2 = dppe; M = Ru, X = Cl, L = PPh3; M = Os, X = Br, L = PPh3; Cp = η-C5H5) with the alkynol HCCCH(OH)(Fc) (1) (Fc = ferrocenyl) in the presence of TlBF4 gave the monosubstituted allenylidene complexes [M(CCCHFc)L2(Cp)][BF4] (2a: M = Ru, L = PPh3; 3: M = Fe, L2 = dppe; 4: M = Os, L = PPh3). Similarly, the reaction of 1 with [RuCl(PPh3)2(Cp)] and NH4PF6 in methanol gave [Ru(CCCHFc)(PPh3)2(Cp)][PF6] (2b). These highly colored compounds were characterized by spectroscopic and electrochemical techniques and in the case of 2b by a single-crystal X-ray structure determination. Cyclic voltammetry in MeCN in the presence of [nBu4N][ClO4] at 100 mV·s−1 shows a reversible ferrocenyl-based one-electron oxidation, in addition to irreversible oxidation and reduction processes. The NMR spectra of 2b show complex behavior at low temperature, attributed to temperature-dependent chemical shifts and correlated motions of the allenylidene ligand and the ferrocenyl substituent. Reactions of the transition metal halide complexes [MXL2(Cp)] (M = Fe, X = I, L2 = dppe; M = Ru, X = Cl, L = PPh3; M = Os, X = Br, L = PPh3, Cp = η-C5H5) with the alkynol HCCCH(OH)(Fc) (Fc = ferrocenyl) in the presence of thallium salts gave the monosubstituted allenylidene complexes [M(CCCHFc)L2(Cp)][BF4]. Similarly, the reaction of the alkynol with [RuCl(PPh3)2(Cp)] and NH4PF6 in methanol gave [Ru(CCCHFc)(PPh3)2(Cp)][PF6]. These highly colored compounds were characterized by spectroscopic and electrochemical techniques and in one case by a single-crystal X-ray structure determination. Cyclic voltammetry in MeCN in the presence of [n-Bu4N][ClO4] at 100 mV·s−1 shows a reversible ferrocenyl-based one-electron oxidation, in addition to irreversible oxidation and reduction processes. [ABSTRACT FROM AUTHOR]

Published
2010
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40. Refining the interpretation of near-infrared band shapes in a polyynediyl molecular wire.

Author

Parthey M, Gluyas JB, Schauer PA, Yufit DS, Howard JA, Kaupp M, and Low PJ

Abstract

Spinning to improve (band) shape: A blend of theoretical and experimental work demonstrates that the rotational conformation of mixed-valence complexes influences the low-energy (NIR) transitions in such molecules. Interpretations of the NIR band shapes are presented., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2013
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