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Peculiar Properties (peculiar + property)
Selected AbstractsSingle particle representation of parabose extension of conformal supersymmetryFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 4-5 2008I. Salom Abstract We consider generalized conformal supersymmetry constructed as parabose N = 4 algebra. It is shown that Green's ansatz representations have, in this context, natural interpretation as multi particle spaces. The simplest nontrivial representation is shown to correspond to a massless particle of arbitrary helicity, and some peculiar properties of this space are pointed out. [source] Localization and interactions of melatonin in dry cholesterol/lecithin mixed reversed micelles used as cell membrane modelsJOURNAL OF PINEAL RESEARCH, Issue 4 2005David Bongiorno Abstract:, The state of melatonin confined in dry cholesterol/lecithin mixed reversed micelles dispersed in CCl4 was investigated using 1H-NMR and FT-IR spectroscopies as a function of the melatonin to lecithin molar ratio (RMLT) and of the cholesterol to lecithin molar ratio (RCHL). An analysis of experimental results leads to the hypothesis that, independent of RMLT and as a consequence of anisotropic melatonin/lecithin, melatonin/cholesterol and cholesterol/lecithin interactions, melatonin is totally solubilized in reversed micelles. Melatonin is mainly located in and oriented in the nanodomain constituted by the hydrophilic groups of cholesterol and lecithin. A competition of melatonin and cholesterol for the hydrophilic binding sites of the reversed micelles was observed by changing the RCHL. Some possible biological implications of the specific interactions governing the solubilization process, the preferential location and the peculiar properties of melatonin confined in cholesterol/lecithin mixed reversed micelles are discussed. [source] Peculiarities of soliton motion in molecular systems with high dispersionPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004V. V. Krasilnikov Abstract In this work, features of propagating protons along molecular chain of hydrogen bonds are described from position of soliton dynamics with taking into account interaction of first and second neighbors of a proton sublattice. It is proposed extension of the model that is an endless chain of water molecules in which formation of hydrogen bonds is due to participating one proton of every water molecule, a second proton no participating in hydrogen bond and being confined by covalent bond of an oxygen atom. Nonlinearity is due to peculiar properties of proton sublattice potential. The model used to obtain continual equations which contain the spatial derivatives of the fourth order that is related with dispersion of longwave oscillations. The availability of such a dispersion changes essentially dynamics of the molecular chain, which allows of manifesting new peculiarities of propagating nonlinear excitations. It is shown there are two new sorts of charge density excitations transferred by solitons determined as exact analytic dependences in such a system. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Structural features for the mechanism of antitumor action of a dimeric human pancreatic ribonuclease variantPROTEIN SCIENCE, Issue 1 2009Antonello Merlino Abstract A specialized class of RNases shows a high cytotoxicity toward tumor cell lines, which is critically dependent on their ability to reach the cytosol and to evade the action of the ribonuclease inhibitor (RI). The cytotoxicity and antitumor activity of bovine seminal ribonuclease (BSRNase), which exists in the native state as an equilibrium mixture of a swapped and an unswapped dimer, are peculiar properties of the swapped form. A dimeric variant (HHP2-RNase) of human pancreatic RNase, in which the enzyme has been engineered to reproduce the sequence of BSRNase helix-II (Gln28,Leu, Arg31,Cys, Arg32,Cys, and Asn34,Lys) and to eliminate a negative charge on the surface (Glu111,Gly), is also extremely cytotoxic. Surprisingly, this activity is associated also to the unswapped form of the protein. The crystal structure reveals that on this molecule the hinge regions, which are highly disordered in the unswapped form of BSRNase, adopt a very well-defined conformation in both subunits. The results suggest that the two hinge peptides and the two Leu28 side chains may provide an anchorage to a transient noncovalent dimer, which maintains Cys31 and Cys32 of the two subunits in proximity, thus stabilizing a quaternary structure, similar to that found for the noncovalent swapped dimer of BSRNase, that allows the molecule to escape RI and/or to enhance the formation of the interchain disulfides. [source] Kinetic and functional analysis of transient, persistent and resurgent sodium currents in rat cerebellar granule cells in situ: an electrophysiological and modelling studyTHE JOURNAL OF PHYSIOLOGY, Issue 1 2006Jacopo Magistretti Cerebellar neurones show complex and differentiated mechanisms of action potential generation that have been proposed to depend on peculiar properties of their voltage-dependent Na+ currents. In this study we analysed voltage-dependent Na+ currents of rat cerebellar granule cells (GCs) by performing whole-cell, patch-clamp experiments in acute rat cerebellar slices. A transient Na+ current (INaT) was always present and had the properties of a typical fast-activating/inactivating Na+ current. In addition to INaT, robust persistent (INaP) and resurgent (INaR) Na+ currents were observed. INaP peaked at ,,40 mV, showed half-maximal activation at ,,55 mV, and its maximal amplitude was about 1.5% of that of INaT. INaR was elicited by repolarizing pulses applied following step depolarizations able to activate/inactivate INaT, and showed voltage- and time-dependent activation and voltage-dependent decay kinetics. The conductance underlying INaR showed a bell-shaped voltage dependence, with peak at ,35 mV. A significant correlation was found between GC INaR and INaT peak amplitudes; however, GCs expressing INaT of similar size showed marked variability in terms of INaR amplitude, and in a fraction of cells INaR was undetectable. INaT, INaP and INaR could be accounted for by a 13-state kinetic scheme comprising closed, open, inactivated and blocked states. Current-clamp experiments carried out to identify possible functional correlates of INaP and/or INaR revealed that in GCs single action potentials were followed by depolarizing afterpotentials (DAPs). In a majority of cells, DAPs showed properties consistent with INaR playing a role in their generation. Computer modelling showed that INaR promotes DAP generation and enhances high-frequency firing, whereas INaP boosts near-threshold firing activity. Our findings suggest that special properties of voltage-dependent Na+ currents provides GCs with mechanisms suitable for shaping activity patterns, with potentially important consequences for cerebellar information transfer and computation. [source] Embedded Phases: A Way to Active and Stable CatalystsCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 1 2010Loredana De, Rogatis Dr. Abstract Industrial catalysts are typically made of nanosized metal particles, carried by a solid support. The extremely small size of the particles maximizes the surface area exposed to the reactant, leading to higher reactivity. Moreover, the higher the number of metal atoms in contact with the support, the better the catalyst performance. In addition, peculiar properties have been observed for some metal/metal oxide particles of critical sizes. However, thermal stability of these nanostructures is limited by their size; smaller the particle size, the lower the thermal stability. The ability to fabricate and control the structure of nanoparticles allows to influence the resulting properties and, ultimately, to design stable catalysts with the desired characteristics. Tuning particle sizes provides the possibility to modulate the catalytic activity. Unique and unexpected properties have been observed by confining/embedding metal nanoparticles in inorganic channels or cavities, which indeed offers new opportunities for the design of advanced catalytic sytems. Innovation in catalyst design is a powerful tool in realizing the goals of more green, efficient and sustainable industrial processes. The present Review focuses on the catalytic performance of noble metal- and non precious metal-based embedded catalysts with respect to traditional impregnated systems. Emphasis is dedicated to the improved thermal stability of these nanostructures compared to conventional systems. [source] Synthesis and Physicochemical Characterization of meso -Functionalized Corroles: Precursors of Organic,Inorganic Hybrid MaterialsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2005Jean-Michel Barbe Abstract Cobalt(III) corroles exhibit an infinite selectivity for the coordination of carbon monoxide towards dioxygen and dinitrogen. This peculiar property thus allows their use as sensing devices for CO detection. Here are described the syntheses and physico-chemical characterization of meso mono-, bis- and tris(triethoxysilyl)-functionalized corroles, precursors of organic,inorganic materials. The corrole ring formation was achieved in every case using the "2+1" method involving the reaction of two equivalents of an encumbered dipyrromethane with one equivalent of an aromatic aldehyde in the presence of a catalytic amount of trifluoroacetic acid. The functionalization of the corrole by triethoxysilyl chains was carried out by a condensation reaction of an isocyanate, bearing a triethoxysilyl termination, either on an amino or hydroxy group. Each final compound and intermediate were characterized by various physico-chemical techniques such as 1H NMR, UV/Vis, MALDI/TOF or EI mass spectrometry and elemental analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] The influence of cholesterol on the interaction of HIV gp41 membrane proximal region-derived peptides with lipid bilayersFEBS JOURNAL, Issue 19 2007Ana S. Veiga A small amino acid sequence (LWYIK) inside the HIV-1 gp41 ectodomain membrane proximal region (MPR) is commonly referred to as a cholesterol-binding domain. To further study this unique and peculiar property we have used fluorescence spectroscopy techniques to unravel the membrane interaction properties of three MPR-derived synthetic peptides: the membrane proximal region peptide-complete (MPRP-C) which corresponds to the complete MPR; the membrane proximal region peptide-short (MPRP-S), which corresponds to the last five MPR amino acid residues (the putative cholesterol-binding domain) and the membrane proximal region peptide-intermediate (MPRP-I), which corresponds to the MPRP-C peptide without the MPRP-S sequence. MPRP-C and MPRP-I membrane interaction is largely independent of the membrane phase. Membrane interaction of MPRP-S occurs for fluid phase membranes but not in gel phase membranes or cholesterol-containing bilayers. The gp41 ectodomain MPR may have a very specific function in viral fusion through the concerted and combined action of cholesterol-binding and non-cholesterol-binding domains (i.e. domains corresponding to MPRP-S and MPRP-I, respectively). [source] | ||||||||||||||||