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Remarkable Stability (remarkable + stability)
Selected AbstractsChemoselective Reagents for Covalent Capture and Display of Glycans in Microarrays,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Emiliano Cló Abstract Glycobiology has made very significant progress in the past decades. However, further progress will significantly depend on the establishment of novel methods for miniaturized, high-throughput analysis of glycan,protein interactions. Robust solid-phase chemical tools and new, chemoselective reagents for biologically meaningful display of surface-immobilized glycans are likely to play a key role. Here we present four new bifunctional linkers that allow highly chemoselective capture of unprotected glycans in solution to form glycan-linker conjugates for direct construction of glycan microarrays (glycochips). The bifunctional linkers carry O -linked aminooxy moieties, some with N -substituents at one end and an amino group at the other. In addition, they contain a substituted benzene ring for UV traceability and improved purification of glycan-linker conjugates. NMR spectroscopic studies in solution proved that N -substituted aminooxy linkers provided model glycan-linker conjugates with the ,-glucopyranoside configuration, i.e. the ring-closed form required for biological recognition. Then an ensemble of glycan-linker conjugates were assembled from mannobiose, lactose, and N -acetyl-lactosamine and used for covalent printing of glycan microarrays. The stability of oximes were studied both in solution and on-chip. In solution, two of the linkers provided glycan-linker conjugates with a remarkable stability at pH 4 or higher, on-chip this relative stability was upheld. Two of the linkers, with different properties, are recommended for the glycobiology toolbox for the construction of glycan microarrays from unprotected glycans. [source] Are cognitive differences between immigrant and majority groups diminishing?EUROPEAN JOURNAL OF PERSONALITY, Issue 5 2004Jan te Nijenhuis A review is given of scores on various cognitive measures, comparing groups of ethnic Dutch and non-Western immigrants using a large number of datasets. The research shows that there are large group differences in school results, work proficiency, and g for Turks, Moroccans, Surinamese, Netherlands Antilleans, and Indonesians from the Moluccans compared with ethnic Dutch. However, South-East Asians score higher, and persons with one immigrant and one ethnic Dutch parent score only slightly below the mean of the Dutch. When comparing first-generation disadvantaged immigrant groups with later generations the data show substantial improvements for g, a remarkable stability of educational differences for younger children, and a clear improvement in educational achievement at the end of primary school. Indirect data on intergenerational improvements in work proficiency appear suggestive of a trend of closing gaps. Some of the data reflect higher cognitive capacities over time, and this enhances integration of immigrants into Dutch society. Causes of group differences and improvements in mean level of g are discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Amorphous Calcium Carbonate is Stabilized in ConfinementADVANCED FUNCTIONAL MATERIALS, Issue 13 2010Christopher J. Stephens Abstract Biominerals typically form within localized volumes, affording organisms great control over the mineralization process. The influence of such confinement on crystallization is studied here by precipitating CaCO3 within the confines of an annular wedge, formed around the contact point of two crossed half-cylinders. The cylinders are functionalized with self-assembled monolayers of mercaptohexadecanoic acid on gold. This configuration enables a systematic study of the effects of confinement since the surface separation increases continuously from zero at the contact point to macroscopic (mm) separations. While oriented rhombohedral calcite crystals form at large (>10,µm) separations, particles with irregular morphologies and partial crystallinity are observed as the surface separation approaches the dimensions of the unconfined crystals (5,10,µm). Further increase in the confinement has a significant effect on the crystallization process with flattened amorphous CaCO3 (ACC) particles being formed at micrometer separations. These ACC particles show remarkable stability when maintained within the wedge but rapidly crystallize on separation of the cylinders. A comparison of bulk and surface free-energy terms shows that ACC cannot be thermodynamically stable at these large separations, and the stability is attributed to kinetic factors. This study therefore shows that the environment in which minerals form can have a significant effect on their stability and demonstrates that ACC can be stabilized with respect to the crystalline polymorphs of CaCO3 by confinement alone. That ACC was stabilized at such large (micrometer) separations is striking, and demonstrates the versatility of this strategy, and its potential value in biological systems. [source] Hexyl-Derivatized Poly(3,4-ethylenedioxyselenophene): Novel Highly Stable Organic Electrochromic Material with High Contrast Ratio, High Coloration Efficiency, and Low-Switching VoltageADVANCED MATERIALS, Issue 17 2009Mao Li A novel family of electrochromic materials has been discovered. The electropolymerized poly(hexyl-3,4-ethylenedioxyselenophene) film switches color between a highly absorbing pure blue and a nearly colorless bleached state, achieves both a high contrast ratio of 88,89% and a high CE of up to 773,cm2 C,1 while showing a fast switching time and remarkable stability with the contrast ratio remaining 48% after 10000 cycles. [source] Electrostatic Assembly of Poly(ethylene glycol) NanotubesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2010Woo-Sik Jang Abstract Poly(ethylene glycol) (PEG)-based films, nanotubes, and nanotube arrays were successfully made using layer-by-layer (LbL) assembly ion-containing PEO derivatives on porous templates and planar substrates. PEG nanotubes are challenging to produce because PEG dissolves into solutions and solvents used during nanotube processing, but our techniques circumvent the issue. Nanotube dimensions were verified using microscopy and the average observed diameter was 155,nm. The PEG-based structures showed remarkable stability in water, salt water, and sodium hydroxide solution. [source] Electron spin resonance study of phosphorus-nitroxides from 1,3-additions of silicon-phosphorus reagents to nitronesMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2004Dr D. Lawrence Haire Abstract This article explores a new, convenient route to ,-phosphorus nitroxides. Specifically, the reaction sequence involves the novel 1,3-addition of trimethylsilyl phosphites (e.g. diethyl) or trimethylsilyl phosphines (e.g. diphenyl) to aldo-nitrones [e.g. ,-phenyl-N- tert -butylnitrone (PBN) or 5,5-dimethyl-l-pyrroline-N-oxide (DMPO)] or keto-nitrones [e.g. 2-ethyl-5,5-dimethyl-1 pyrroline-N-oxide (2-Et-DMPO) or 2-phenyl-5,5-dimethyl-l-pyrroline-N-oxide (2-Ph-DMPO)] to form ,-phosphityl- or ,-phosphinyl-O-silylhydroxylamines. Acidic hydrolysis provides the corresponding hydroxylamines that are easily oxidized to the title ,-phosphorus-nitroxides. ESR spectroscopic analysis revealed some very large ,-phosphorus hyperfine splittings (i.e. in excess of 5 mT). For this reason and their remarkable stability (persistence) some of these nitroxides show promise as integral components in new, improved weak-field dynamic nuclear polarization (DNP) magnetometers. Copyright © 2004 John Wiley & Sons, Ltd. [source] Structural stability and heat-induced conformational change of two complement inhibitors: C4b-binding protein and factor HPROTEIN SCIENCE, Issue 5 2004Lena Kask C4BP, C4b-binding protein; FH, factor H; CCP, complement control protein; CD, circular dichroism; FTIR, Fourier transform-infrared spectroscopy; PT, prothrombin; VCP, vaccinia virus complement control protein Abstract The complement inhibitors C4b-binding protein (C4BP) and factor H (FH) both consist of complement control protein (CCP) domains. Here we examined the secondary structure of both proteins by circular dichroism and Fourier-transform infrared technique at temperatures ranging from 30°C,90°C. We found that predominantly ,-sheet structure of both proteins was stable up to 70°C, and that a reversible conformational change toward ,-helix was apparent at temperatures ranging from 70°C to 90°C. The ability of both proteins to inhibit complement was not impaired after incubation at 95°C, exposure to extreme pH conditions, and storage at room temperature for several months. Similar remarkable stability was previously observed for vaccinia virus control protein (VCP), which is also composed of CCP domains; it therefore seems to be a general property of CCP-containing proteins. A typical CCP domain has a hydrophobic core, which is wrapped in ,-sheets and stabilized by two disulphide bridges. How the CCP domains tolerate harsh conditions is unclear, but it could be due to a combination of high content of prolines, hydrophobic residues, and the presence of two disulphide bridges within each domain. These findings are of interest because CCP-containing complement inhibitors have been proposed as clinical agents to be used to control unwanted complement activation that contributes to many diseases. [source] Crystallization and preliminary X-ray analysis of carnein, a serine protease from Ipomoea carneaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 4 2009Ashok Kumar Patel Carnein is an 80,kDa subtilisin-like serine protease from the latex of the plant Ipomoea carnea which displays an exceptional resistance to chemical and thermal denaturation. In order to obtain the first crystal structure of a plant subtilisin and to gain insight into the structural determinants underlying its remarkable stability, carnein was isolated from I. carnea latex, purified and crystallized by the hanging-drop vapour-diffusion method. A data set was collected to 2.0,Å resolution in-house from a single crystal at 110,K. The crystals belonged to the trigonal space group P3121 or P3221, with unit-cell parameters a = b = 126.9, c = 84.6,Å, , = , = 90, , = 120°. Assuming the presence of one molecule per asymmetric unit, the Matthews coefficient is 2.46,Å3,Da,1, corresponding to a solvent content of 50%. Structure determination of the enzyme is in progress. [source] Strategic Management Upside Down: Tracking Strategies at McGill University from 1829 to 1980CANADIAN JOURNAL OF ADMINISTRATIVE SCIENCES, Issue 4 2003Henry Mintzberg A number of the fundamental premises of strategic management are put into question in a study that tracks the realized strategies of a prominent university over a century and an half. Amidst continual change in detail, there was remarkable stability in the aggregate, and nothing resembling quantum or revolutionary change in strategy ever occurred. This may be explained in some of the terms most popular in business today: "empowerment", "venturing", and especially "knowledge work". Thus, while the typical university may seem very different from the typical corporation, its behaviour may in fact contain sobering messages for the strategic management of businesses. Résumé Le present article suit, sur une periode de plus d'un siecle et demi, I'evolution des strategies d'une universite bien connue et remet en question un certain nombre de premisses elementaires de la gestion strategique. Au cæur d'incessants changements qui affectent les details, on note dans l'ensemble une remarquable stabilite et l'absence de tout changement global ou revolutionnaire dans la strategie. Cette situation peut s'expliquer par les termes les plus en vogue, de nos jours, dans le milieu d'affaires, a savoir: « autonomisation », « developpement commercial », et tout particulierement « travail intellectuel ». Donc, bien que l'universite type puisse paraitre bien distincte de la compagnie type, son comportement peut en fait contenir d'importants messages pour la gestion strategique des entreprises. [source] Latent Blue and Red Fluorophores Based on the Trimethyl LockCHEMBIOCHEM, Issue 8 2006Luke D. Lavis Unlocking fluorescence. The "trimethyl lock" is an effective way to mask structurally diverse fluorescent molecules for the preparation of fluorogenic enzyme substrates. These novel probes exhibit remarkable stability in water, and this makes them useful for a variety of biochemical and biological applications. [source] 2232: Why are retinal pigment epithelial cells so resistant to oxidative stress?ACTA OPHTHALMOLOGICA, Issue 2010U BRUNK Purpose The functional integrity of postmitotic retinal pigment epithelial (RPE) cells is crucial for photoreceptor survival, and RPE malfunction is considered an important factor behind age-related macular degeneration (AMD). Although RPE cells daily phagocytose large amounts of fatty acid-rich distal photoreceptor material, their lysosomal accumulation of lipofuscin (LF) is nevertheless slow. Only late in life do humans have LF-loaded RPE cells, which then not only have a reduced capacity to endocytose photoreceptor material but also are less capable of keeping up with normal autophagy. The latter activity is important for normal turnover of the cell's own components. Methods ARPE-19 cells in culture were evaluated with respect to lysosomal stability at oxidative stress. Redox-active iron, autophagic activity (evaluation of LC3-I and LC3-II protein), and anti-oxidative proteins were assayed using cytochemistry (Sulphide-Silver Method), electron spin resonance (ESR) and western blotting for a variety of stress proteins. Results The lysosomal compartment of the ARPE-19 cells was found remarkably resistant to oxidative stress. The SSM and ESR methods suggested low lysosomal amounts of redox-active iron and no enhanced autophagy following oxidative stress. The normal autophagy rate was higher than in other professional scavengers. Conclusion The found low amount of lysosomal redox-active iron explains the slow formation of lipofuscin over time and the remarkable stability that ARPE-19 cells and their lysosomes show even under severe oxidative stress. The molecular mechanisms behind this phenomenon may be an unusual capacity to quickly export low mass iron from lysosomes to the cytosol and/or a high normal degree of autophagy of iron-binding stress proteins. [source] A General Route to Fully Terminally tert -Butylated Linear Polyenes,CHEMISTRY - A EUROPEAN JOURNAL, Issue 34 2010Dagmar Klein Abstract Starting from the readily available ,,,-unsaturated ketone, 3- tert -butyl-4,4-dimethyl-2-pentenal, higher vinylogues, and fully terminally tert -butylated polyolefins with up to 13 consecutive conjugated double bonds have been prepared by either McMurry dimerization or Wittig chain-elongation routes. The highly unsaturated conjugated , systems, which show a remarkable stability, have been characterized by spectroscopic methods and, in many cases, by X-ray structural analysis. The yields are high enough to allow for thorough chemical reactivity studies. [source] | |||||||||||||