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Berlin Brandenburg

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  • American Chemical Society (CrossRef)  (48)
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  • 1
    Language: English
    In: Analytical chemistry, 05 June 2018, Vol.90(11), pp.6975-6983
    Description: Understanding the mechanisms behind amyloid protein aggregation in diseases, such as Parkinson's and Alzheimer's disease, is often hampered by the reproducibility of in vitro assays. Yet, understanding the basic mechanisms of protein misfolding is essential for the development of novel therapeutic strategies. We show here, that for the amyloid protein α-synuclein (aSyn), a protein involved in Parkinson's disease (PD), chromatographic buffers and storage conditions can significantly interfere with the overall structure of the protein and thus affect protein aggregation kinetics. We apply several biophysical and biochemical methods, including size exclusion chromatography (SEC), dynamic light scattering (DLS), and atomic force microscopy (AFM), to characterize the high molecular weight conformers formed during protein purification and storage. We further apply hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to characterize the monomeric form of aSyn and reveal a thus far unknown structural component of aSyn at the C-terminus of the protein. Furthermore, lyophilizing the protein greatly affected the overall structure of this monomeric conformer. We conclude from this study that structural polymorphism may occur under different storage conditions, but knowing the structure of the majority of the protein at the start of each experiment, as well as the factors that may influence it, may pave the way to an improved understanding of the mechanism leading to aSyn pathology in PD.
    Keywords: Freezing ; Alpha-Synuclein -- Analysis
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 2
    Language: English
    In: The Journal of Physical Chemistry C, 04/08/2010, Vol.114(13), pp.5804-5810
    Description: The nature of observed growth of solid carbon on palladium from ethylene−hydrogen mixtures is consistent with the supposition that the primary source of carbon for growth is homogeneously generated radicals. Evidence includes the lack of growth in the absence of a reacting mixture, sharp maxima as a function of temperature, and dramatic differences in temperature of growth as a function of mixture composition. The finding that the structure of the support strongly influenced the morphology of the solid carbon, and the temperature regime for deposition, is also consistent with this model. Carbon nanofibers were found to form on sputtered palladium films and palladium nanopowder (ca. 700 °C), whereas planar carbon structures deposited on palladium micrometer powder and foil (ca. 600 °C). A radical species growth mechanism is consistent not only with observations made herein but also with data presented in earlier studies.
    Keywords: Chemistry;
    ISSN: 1932-7447
    E-ISSN: 1932-7455
    Source: American Chemical Society (via CrossRef)
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  • 3
    Language: English
    In: Analytical chemistry, 21 February 2017, Vol.89(4), pp.2361-2368
    Description: Antibodies are an important class of drugs, comprising more than half of all new FDA approvals. Therapeutic antibodies must be chemically stable both in storage and in vivo, following administration to patients. Deamidation is a major degradation pathway for all natural and therapeutic proteins circulating in blood. Here, the linkage between deamidation propensity and structural dynamics is investigated by examining two antibodies with differing specificities. While both antibodies share a canonical asparagine-glycine (NG) motif in a structural loop, this is prone to deamidation in one of the antibodies but not the other. We found that the hydrogen-exchange rate at the adjacent two amides, often the autocatalytic nucleophiles in deamidation, correlated with the rate of degradation. This previously unreported observation was confirmed upon mutation to stabilize the deamidation lability via a generally applicable orthogonal engineering strategy presented here. We anticipate that the structural insight into chemical degradation in full-length monoclonal antibodies and the high-resolution hydrogen-exchange methodology used will have broad application across biochemical study and drug discovery and development.
    Keywords: Amides–Chemistry ; Antibodies, Monoclonal–Metabolism ; Asparagine–Chemistry ; Catalysis–Metabolism ; Deuterium Exchange Measurement–Chemistry ; Humans–Metabolism ; Immunoglobulin G–Chemistry ; Mass Spectrometry–Metabolism ; Mass Spectrometry–Methods ; Amides ; Antibodies, Monoclonal ; Immunoglobulin G ; Asparagine;
    ISSN: 00032700
    E-ISSN: 1520-6882
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  • 4
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 17 February 2004, Vol.20(4), pp.1189-93
    Description: Hydrogen spillover over macroscopic distances was demonstrated and exploited in the design of two novel catalytic reactors for 1-butene isomerization. A dual-bed reactor containing separate zones of noble metal and bimetallic catalysts yielded activities up to 2.7 times greater than that of the noble metal alone. The noble metal catalyst contained palladium supported on graphitic carbon. The bimetallic catalyst contained a base metal, either iron or cobalt, and a lanthanide metal, either cerium or praseodymium, also supported on graphitic carbon. The bimetallic catalysts by themselves had no measurable activity at the current experimental conditions. Results from a dual-bed, dual-feed reactor using the same catalysts showed dramatic activity increases relative to controls. In this reactor, the hydrocarbon never contacted the noble metal catalyst, yet substantial hydrocarbon conversion was measured. No hydrocarbon conversion was detected when blank support replaced the bimetallic catalyst or when no material at all was placed above the noble metal catalyst. In both reactors, the activity increase was attributed to hydrogen spillover. That is, molecular hydrogen adsorbed and dissociated on the noble metal catalyst. The adsorbed atomic hydrogen was then transported via surface diffusion to the bimetallic catalyst, activating those sites. The results also demonstrated that a catalytic reaction may occur at distinctly different reactive sites and that catalysts may be selected to promote specific steps within the reaction.
    Keywords: Chemistry;
    ISSN: 0743-7463
    E-ISSN: 15205827
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  • 5
    Language: English
    In: Langmuir, 02/1997, Vol.13(3), pp.477-482
    ISSN: 0743-7463
    E-ISSN: 1520-5827
    Source: American Chemical Society (via CrossRef)
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  • 6
    Language: English
    In: Journal of Physical Chemistry B, August 31, 2000, Vol.104(34), p.8170(7)
    Description: An attempt is made to investigate the adsorption of water on chemically modified, high surface area carbons by employing microcalorimetric techniques. Three mechanisms of water adsorption are detailed according to measured differential heats of adsorption (H (sub ads)).
    Keywords: Surface Chemistry -- Analysis ; Adsorption -- Methods ; Carbon -- Thermal Properties
    ISSN: 1520-6106
    ISSN: 10895647
    E-ISSN: 15205207
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  • 7
    Language: English
    In: Langmuir, 01/1996, Vol.12(11), pp.2756-2761
    ISSN: 0743-7463
    E-ISSN: 1520-5827
    Source: American Chemical Society (via CrossRef)
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  • 8
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 19 June 2007, Vol.23(13), pp.7055-64
    Description: Ceria-alumina particles of a wide variety of structures, from micrometer-sized hollow spheres to nanoparticles, were produced from aerosols of different natures, but all derived from nitrate salts passed through a low power (〈1000 W) atmospheric pressure plasma torch. The amount of water present with the nitrate salts was found to significantly affect the morphology of the resulting material. A model was proposed that explains the mechanism in which water acts as a blowing agent to create hollow metal oxide spheres that then shatter to form metal oxide nanoparticles. Further examination of the nanoparticles revealed that they display a core/shell morphology in which the core material is crystalline CeO2 and the shell material is amorphous Al2O3. These unique core/shell materials are interesting candidates for catalyst support materials with high thermal durability. In addition, experiments have shown that the nanoparticles can be readily converted into CeAlO3 perovskite.
    Keywords: Aerosol ; Aluminiumoxid ; Amorpher Stoff ; Atmosphärendruck ; Ceraluminat ; Ceroxid ; Hohlkugel ; Katalysatorträger ; Kern-Mantel-Struktur ; Kristalliner Stoff ; Mechanismus ; Mikrometerbereich ; Morphologie ; Nanopartikel ; Nitrat ; Perowskit ; Plasmabrenner ; Teilchengröße ; Thermische Stabilität ; Wassergehalt ; Chemistry;
    ISSN: 0743-7463
    E-ISSN: 15205827
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  • 9
    Language: English
    In: Langmuir : the ACS journal of surfaces and colloids, 07 November 2006, Vol.22(23), pp.9694-703
    Description: It is shown that self-supporting graphitic structures of specific shape can be grown in a variety of forms, from nanoscale to macroscale, on metal templates, in a fuel-rich mixture of ethylene and oxygen at temperatures between 750 and 900 K. The evidence presented suggests graphite can be grown in any shape created from catalytic metals (e.g., Ni) under the proper conditions of temperature and gas composition. Structures produced include macroscale bodies, centimeters in dimension, composed of micrometer-scale graphite elements such as graphite "foam" and regular graphite "lattices". Nanoscale hollow graphite spheres were also produced. The production rate in the apparatus employed was roughly shown to be 1 layer/s and was steady with time over several hours. The process of producing self-supporting bodies generally produces hollow graphite structures, as the underlying metal template must be removed by acid following the completion of graphite growth. The process is believed to be possible only in an environment, such as combustion, in which a high concentration of particular radical species is present in the vicinity of the template surface. The following process is postulated: (i) a single layer of graphite is formed from gas-phase radicals by the catalytic action of the metal template, (ii) additional graphite growth is "autocatalytic" and occurs via the decomposition of radicals on the surface and the incorporation of "free" carbon atoms, or other radical fragments, into "edge sites" on the graphite surface.
    Keywords: Abscheidung (Beschichten) ; Anwendung in Der Elektrotechnik Und Elektronik ; Ethylen ; Formgebung ; Gittergeometrie ; Graphitgefüge ; Hochauflösende Transmissionselektronenmikroskopie ; Hohlkugel ; Katalytische Verbrennung ; Kohlenstoff ; Nanostruktur ; Nickel ; Niedrigtemperatur ; Radikal (Chemisch) ; Rasterelektronenmikroskopie ; Sauerstoff ; Schablone ; Schaum ; Wachstumsgeschwindigkeit ; Chemistry;
    ISSN: 0743-7463
    E-ISSN: 15205827
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  • 10
    Language: English
    In: The Journal of Physical Chemistry C, 12/11/2008, Vol.112(49), pp.19405-19411
    ISSN: 1932-7447
    E-ISSN: 1932-7455
    Source: American Chemical Society (via CrossRef)
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