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Different Modifications (different + modifications)
Selected AbstractsCo-expression of C-terminal truncated alpha-synuclein enhances full-length alpha-synuclein-induced pathologyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2010Ayse Ulusoy Abstract Lewy bodies, which are a pathological hallmark of Parkinson's disease, contain insoluble polymers of alpha-synuclein (,syn). Among the different modifications that can promote the formation of toxic ,syn species, C-terminal truncation is among the most abundant alterations in patients with Parkinson's disease. In vitro, C-terminal truncated ,syn aggregates faster and sub-stoichiometric amounts of C-terminal truncated ,syn promote aggregation of the full-length ,syn (,synFL) and induce neuronal toxicity. To address in vivo the putative stimulation of ,syn-induced pathology by the presence of truncated ,syn, we used recombinant adeno-associated virus to express either ,synFL or a C-terminal truncated ,syn (1-110) in rats. We adjusted the recombinant adeno-associated virus vector concentrations so that either protein alone led to only mild to moderate axonal pathology in the terminals of nigrostriatal dopamine neurons without frank cell loss. When these two forms of ,syn were co-expressed at these pre-determined levels, it resulted in a more aggressive pathology in fiber terminals as well as dopaminergic cell loss in the substantia nigra. Using an antibody that did not detect the C-terminal truncated ,syn (1-110) but only ,synFL, we demonstrated that the co-expressed truncated protein promoted the progressive accumulation of ,synFL and formation of larger pathological accumulations. Moreover, in the co-expression group, three of the eight animals showed apomorphine-induced turning, suggesting prominent post-synaptic alterations due to impairments in the dopamine release, whereas the mild pathology induced by either form alone did not cause motor abnormalities. Taken together these data suggest that C-terminal truncated ,syn can interact with and exacerbate the formation of pathological accumulations containing ,synFL in vivo. [source] Synthesis of the Carbon Framework of the Stephaoxocanes Employing a Sequential RCM/Pomeranz,Fritsch ApproachEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2007Andrea B. J. Bracca Abstract The syntheses of two cyclodeca[ij]isoquinoline derivatives, which embody the carbon framework of stephaoxocanidine, excentricine and the recently isolated stephalonganines A, B and C, are reported. The target tricyclic compounds were prepared from isovanillin, employing a ring-closing metathesis approach towards the synthesis of a benzocyclodecane-type common intermediate; different modifications of thePomeranz,Fritsch protocol allowed the installation of the heterocyclic ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Second law analysis of hydrogen liquefiers operating on the modified Collins cycleINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 11 2001M. T. Syed Abstract Hydrogen liquefaction systems have been the subject of intense investigations for many years. Some established gas liquefaction systems, such as the precooled Linde,Hampson systems, are not used for hydrogen liquefaction in part because of their relatively low efficiencies. Recently, more promising systems employing the modified Collins cycle have been introduced. This paper reports on second law analyses of a hydrogen liquefier operating on the modified Collins cycle. Two different modifications employing the cycle in question were attempted: (1) a helium-refrigerated hydrogen liquefaction system and (2) a hydrogen-refrigerated hydrogen liquefaction system. Analyses were carried out in order to identify potential areas of development and efficiency improvement. A computer code capable of computing system and component efficiencies; exergy losses; and optimum number and operating conditions of compressors, expanders, aftercoolers, intercoolers, and Joule,Thomson valves was developed. Evaluation of the thermodynamic and transport properties of hydrogen at different temperature levels was achieved by employing a hydrogen property code developed by researchers at the National Bureau of Standards (currently NIST). A parametric analysis was carried out and optimal decision rules pertaining to system component selection and design were reached. Economic analyses were also reported for both systems and indicated that the helium-refrigerated hydrogen liquefier is more economically feasible than the hydrogen-refrigerated hydrogen liquefier. Copyright © 2001 John Wiley & Sons, Ltd. [source] Properties modification of PET vascular prosthesesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 5 2009W. Chaouch Abstract Aging mechanisms have been investigated on polyethylene terephthalate (PET) fibres extracted from various vascular prostheses in order to identify the different modifications of the material's degradation. NMR spectroscopy provides a comprehensive view of chemical structures of macromolecules. Examination of a series of PET fibres showed significant chemical differences between the virgin prostheses and the explants, especially for diethylene glycol (DEG) and cyclic oligomeric groups. These analyses revealed that PET failures in vascular prostheses are susceptible to hydrolysis during in vivo stay. We also extended this 1H NMR technique to determine the hydroxyl and carboxyl end-group concentrations. In order to validate the 1H NMR results, complementary techniques , chemical titration and classical viscosimetry , were used. The obtained results showed an increase in end-group concentrations and a decrease of the viscosity averaged macromolecular weight (M,) for the explants. Copyright © 2009 John Wiley & Sons, Ltd. [source] Atomvolumen, Packungsdichte der Atome und chemische Bindung in nichtmetallischen ElementenACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2007M. Trömel The atomic volume of crystalline elements is largely determined by the packing density of atoms in the respective modification. The determination of packing density is improved by assuming that the atomic distances depend on bond valences according to Pauling's equation. With the additional assumption of equal valence in different modifications, the experimental atomic volume of an element in any given structure is reduced to its volume in close-packed structures, e.g. f.c.c. The ratio of this reduced atomic volume and the experimental atomic volume is a measure of packing density. Reduced atomic volumes of C, Si, Ge, P, As, S and Se, as calculated from different modifications, correspond in most cases to within less than ±1% for each element, even if calculated from extremely different structures like diamond and buckminsterfullerene in the case of carbon, or from numerous modifications of sulfur with annular molecules of different sizes. Exceptions (graphite, white phosphorus, tin and selenium) indicate deviating valences. [source] | ||||||||||