Glycerol dehydration catalyzed by MWW zeolites and the changes in the catalyst deactivation caused by porosity modification

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ethanol steam reforming over rhodium and cobalt-based catalysts: Effect of the support

The effect of support on the properties of rhodium and cobalt-based catalysts for ethanol steam reforming was studied in this work, by comparing the use of magnesia, alumina and Mg-Al oxide (obtained from hydrotalcite) as supports. It was found that metallic rhodium particles with around 2.4-2.6 nm were formed on all supports, but Mg-Al oxide led to the narrowest particles size distribution; cobalt was supposed to be located on the support, affecting its acidity. Rhodium interacts strongly with the support in the order: alumina> Mg-Al oxide > magnesia. The magnesium-containing catalysts showed low ethene selectivity and high hydrogen selectivity while the alumina-based ones showed high ethene selectivity, assigned to the Lewis sites of alumina. The Mg-Al oxide-supported rhodium and cobalt catalyst was the most promising sample to produce hydrogen by ethanol reforming, showing the highest hydrogen yield, low ethene selectivity and high specific surface area during reaction. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Synthese von Sialyl-Lewis X -Glycopeptiden und -Mimetika als Zelladhäsionsinhibitoren für E-Selektin

Die Selektine initiieren im Verlauf von Entzündungsprozessen einen ersten Zellkontakt zwischen Leukozyten und Endothelzellen und ermöglichen so die Auswanderung der Leukozyten aus den Blutgefäßen in das umliegende Gewebe, wo sie ihre immunologische Wirkung entfalten können. Viele Krankheiten gehen allerdings mit einer übermäßigen, durch Selektine vermittelten Zelladhäsion einher. Daher war es das Ziel dieser Arbeit, Selektininhibitoren zu synthetisieren, die pathologische Zelladhäsionsprozesse, wie man sie z.B. bei rheumatoider Arthritis, bei Erkrankungen der Herzkranzgefäße oder im Verlauf von Tumormetastasierungen findet, unterbinden können. Als Leitstruktur für solche Inhibitoren dient das auf den natürlichen Selektinliganden vorkommende Tetrasaccharid Sialyl-Lewis-X. Sialyl-Lewis-X stellt aber nur einen Teil der natürlichen Selektinliganden dar. Es bindet auch nur im millimolaren Bereich an die Selektine. Die komplexen natürlichen Selektinliganden wie z.B. ESL-1 (E-Selektin-Ligand-1), die an verschiedenen Glycosylierungs-stellen des Glycoproteins Sialyl-Lewis-X präsentieren, binden mit deutlich höherer Affinität an die Selektine. Für eine spezifische Rezeptorbindung sind daher außer dem Tetrasaccharid weitere Partialstrukturen verantwortlich, wobei gezeigt werden konnte, dass ein Anknüpfen von Sialyl-Lewis-X-Derivaten an die Partialsequenz 672-681 des ESL-1 eine Affinitätssteigerung hervorruft. Ein weiterer Nachteil des natürlichen Sialyl-Lewis-X-Tetrasaccharids im Hinblick auf seine pharmakologische Verwendung besteht darin, dass sowohl die fucosidische Bindung als auch die glycosidische Verknüpfung zur Neuraminsäure durch Enzyme leicht gespalten werden, wodurch Sialyl-Lewis-X als potenzielles Anti-Adäsionsmolekül an Wert verliert. Um die Kohlenydratliganden vor einem solchen enzymatischen Abbau zu bewahren, wurden in dieser Arbeit neben der im Sialyl-Lewis-X vorliegenden L-Fucose die im Menschen nicht vorkommenden Kohlenhydrate D-Arabinose und L-Galactose sowie neben der Neuraminsäure die (S)-Cyclohexylmilchsäure zur Herstellung der sechs Glycopeptid-Selektinliganden 1-6 mit der Partialsequenz 672-681 des ESL-1 verknüpft. Die Tetrasaccharide und Tetrasaccharid-Mimetika können aus den geschützten Monosacchariden und der geschützten Cyclohexylmilch-säure in parallelen Synthesen im Gramm-Maßstab hergestellt werden. Die automatisierten Glycopeptid-Festphasensynthesen wurden an einem Peptidsynthesizer nach der Fmoc-Strategie unter Verwendung von mit Asparaginsäure vorbeladenen TentaGel®-Harzen durchgeführt. Die Strukturen aller sechs Glycopeptide 1-6 wurden sowohl durch hoch auflösende massenspektrometrische Analysen als auch durch ein- und zweidimensionale NMR-Experimente belegt. Als Ergebnis dieser Arbeit liegen sechs Sialyl-Lewis-X-Glycopeptide und -Mimetika mit der Partialsequenz 672-681 des ESL-1 vor. Diese werden in Kürze auf ihre Wirksamkeit als Zelladhäsions-inhibitoren für E-Selektin getestet. Daraus sollen sich Erkenntnisse über Struktur-Wirkungs-Beziehungen gewinnen lassen, insbesondere was das kooperative Zusammenwirken von Saccharid- und Peptidteilstrukturen in der Erkennung der Liganden durch das E-Selektin anbetrifft.

Additions- und Umlagerungsreaktionen des Lewis-aciden Dihypersilylplumbandiyls in Umsetzungen mit monodenten und ambidenten Lewis-Basen

Die chemische Reaktivität des Dihypersilylplumbylens Pb[Si(Si(CH3)3)3]2 wird durch seine besondere elektronische Struktur bestimmt. Im Unterschied zu Carbenen (Triplett-Grundzustand) liegen Plumbylene im Grundzustand als Singulett vor, mit einem energetisch hochliegenden HOMO (freies Elektronenpaar mit hohem s-Charakter) und einem tiefliegenden LUMO (näherungsweise: freies p-Orbital des Pb-Atoms). Daraus resultiert das amphotere Lewis-Säure/Lewis-Base-Verhalten der Verbindung, mit der Besonderheit, dass sich die beiden Lewis-Zentren am selben Atom befinden. rnIn Umsetzungen mit monodenten und ambidenten Lewis-Basen wurden die Lewis-aciden Eigenschaften des Dihypersilylplumbandiyls Pb[Si(Si(CH3)3)3]2 untersucht. Reaktionen mit den sterisch anspruchsvollen O-Nucleophilen KOtBu (Kalium-tert-Butanolat) und KOiPrPh (4-Kaliumisopropylphenolat) führten bei tiefen Temperaturen zur primären Adduktbildung. Die aus der Strukturanalyse erhaltenen Bindungsdaten zeigen die extreme sterische Überfrachtung des zentralen Blei-Atoms. Der Abbau der sterischen Spannung ist möglicherweise die Ursache für offensichtlich stattfindende Umlagerungsfolgereaktionen (bei Reaktionsführungen bei T>-60°C), die aufgrund spektroskopische Untersuchungen zu vermuten sind.rnEingehender wurden diese Umlagerungsreaktionen in Umsetzungen des Pb[Si(Si(CH3)3)3]2 mit ambidenten Lewis-Basen untersucht. In Übereinstimmung und Erweiterung mit früheren Ergebnissen von Klinkhammer (K. Klinkhammer, Polyhedron, 2002, 21, 587) konnte beispielsweise die Migration einer (mit der ambidenten Lewis-Base tert-Butylisonitril) bzw. beider Hypersilylgruppen (mit p-Tolylisocyanat) unter Bildung hetero- bzw. homoleptischer Plumbylene nachgewiesen werden.rnReaktionen des Pb[Si(Si(CH3)3)3]2 mit den anorganischen ambidenten Salz-Ionen CN-, OCN-, SCN-, N3-, NO2- führen zur Bildung salzartiger Plumbanide der Zusammensetzung Me{Pb[Si(Si(CH3)3)3]2}Nu (Me: Na bzw. K, Nu: CN, OCN, SCN, N3, NO2). Die Verbindungen liegen im Kristall monomer als Kontaktionenpaar vor. Auf diese Weise gelang erstmalig die gezielte Synthese eines Blei(II)cyanids sowie die Darstellung eines Blei(II)isocyanats. rn

The GABAB1b isoform mediates long-lasting inhibition of dendritic Ca2+ spikes in layer 5 somatosensory pyramidal neurons

The apical tuft of layer 5 pyramidal neurons is innervated by a large number of inhibitory inputs with unknown functions. Here, we studied the functional consequences and underlying molecular mechanisms of apical inhibition on dendritic spike activity. Extracellular stimulation of layer 1, during blockade of glutamatergic transmission, inhibited the dendritic Ca2+ spike for up to 400 ms. Activation of metabotropic GABAB receptors was responsible for a gradual and long-lasting inhibitory effect, whereas GABAA receptors mediated a short-lasting (approximately 150 ms) inhibition. Our results suggest that the mechanism underlying the GABAB inhibition of Ca2+ spikes involves direct blockade of dendritic Ca2+ channels. By using knockout mice for the two predominant GABAB1 isoforms, GABAB1a and GABAB1b, we showed that postsynaptic inhibition of Ca2+ spikes is mediated by GABAB1b, whereas presynaptic inhibition of GABA release is mediated by GABAB1a. We conclude that the molecular subtypes of GABAB receptors play strategically different physiological roles in neocortical neurons.

Liver repopulation with bone marrow derived cells improves the metabolic disorder in the Gunn rat

BACKGROUND: Reversible ischaemia/reperfusion (I/R) liver injury has been used to induce engraftment and hepatic parenchymal differentiation of exogenous beta2-microglubulin(-)/Thy1(+) bone marrow derived cells. AIM: To test the ability of this method of hepatic parenchymal repopulation, theoretically applicable to clinical practice, to correct the metabolic disorder in a rat model of congenital hyperbilirubinaemia. METHODS AND RESULTS: Analysis by confocal laser microscopy of fluorescence labelled cells and by immunohistochemistry for beta2-microglubulin, 72 hours after intraportal delivery, showed engraftment of infused cells in liver parenchyma of rats with I/R, but not in control animals with non-injured liver. Transplantation of bone marrow derived cells obtained from GFP-transgenic rats into Lewis rats resulted in the presence of up to 20% of GFP positive hepatocytes in I/R liver lobes after one month. The repopulation rate was proportional to the number of transplanted cells. Infusion of GFP negative bone marrow derived cells into GFP positive transgenic rats resulted in the appearance of GFP negative hepatocytes, suggesting that the main mechanism underlying parenchymal repopulation was differentiation rather than cell fusion. Transplantation of wild type bone marrow derived cells into hyperbilirubinaemic Gunn rats with deficient bilirubin conjugation after I/R damage resulted in 30% decrease in serum bilirubin, the appearance of bilirubin conjugates in bile, and the expression of normal UDP-glucuronyltransferase enzyme evaluated by polymerase chain reaction. CONCLUSIONS: I/R injury induced hepatic parenchymal engraftment and differentiation into hepatocyte-like cells of bone marrow derived cells. Transplantation of bone marrow derived cells from non-affected animals resulted in the partial correction of hyperbilirubinaemia in the Gunn rat.

The utility of preoperative six-minute-walk distance in lung transplantation

RATIONALE The use of 6-minute-walk distance (6MWD) as an indicator of exercise capacity to predict postoperative survival in lung transplantation has not previously been well studied. OBJECTIVES To evaluate the association between 6MWD and postoperative survival following lung transplantation. METHODS Adult, first time, lung-only transplantations per the United Network for Organ Sharing database from May 2005 to December 2011 were analyzed. Kaplan-Meier methods and Cox proportional hazards modeling were used to determine the association between preoperative 6MWD and post-transplant survival after adjusting for potential confounders. A receiver operating characteristic curve was used to determine the 6MWD value that provided maximal separation in 1-year mortality. A subanalysis was performed to assess the association between 6MWD and post-transplant survival by disease category. MEASUREMENTS AND MAIN RESULTS A total of 9,526 patients were included for analysis. The median 6MWD was 787 ft (25th-75th percentiles = 450-1,082 ft). Increasing 6MWD was associated with significantly lower overall hazard of death (P < 0.001). Continuous increase in walk distance through 1,200-1,400 ft conferred an incremental survival advantage. Although 6MWD strongly correlated with survival, the impact of a single dichotomous value to predict outcomes was limited. All disease categories demonstrated significantly longer survival with increasing 6MWD (P ≤ 0.009) except pulmonary vascular disease (P = 0.74); however, the low volume in this category (n = 312; 3.3%) may limit the ability to detect an association. CONCLUSIONS 6MWD is significantly associated with post-transplant survival and is best incorporated into transplant evaluations on a continuous basis given limited ability of a single, dichotomous value to predict outcomes.

Protective DNA vaccination against organ-specific autoimmunity is highly specific and discriminates between single amino acid substitutions in the peptide autoantigen

DNA vaccines that encode encephalitogenic sequences in tandem can protect from subsequent experimental autoimmune encephalomyelitis induced with the corresponding peptide. The mechanism for this protection and, in particular, if it is specific for the amino acid sequence encoding the vaccine are not known. We show here that a single amino acid exchange in position 79 from serine (nonself) to threonine (self) in myelin basic protein peptide MBP68–85, which is a major encephalitogenic determinant for Lewis rats, dramatically alters the protection. Moreover, vaccines encoding the encephalitogenic sequence MBP68–85 do not protect against the second encephalitogenic sequence MBP89–101 in Lewis rats and vice versa. Thus, protective immunity conferred by DNA vaccination exquisitely discriminates between peptide target autoantigens. No bystander suppression was observed. The exact underlying mechanisms remain elusive because no simple correlation between impact on ex vivo responses and protection against disease were noted.

Goya's late masterpiece : head of a monk

Francisco Goya painted few canvases during the last four years of his life spent in France. Several of his late masterpieces have fallen under scrutiny over the past ten years, their authenticity questioned by internationally respected scholars. Goya’s Head of a Monk can be counted among this group of disputed canvases. However, a comparison of the Monk with the artist’s sketchbooks, miniatures and murals created during his time in France as well as his last few years in Madrid indicate that this image as well as its underpainting were created by the master himself toward the end of his career.

Ammonia removal using activated carbons: effect of the surface chemistry in dry and moist conditions

The effect of surface chemistry (nature and amount of oxygen groups) in the removal of ammonia was studied using a modified resin-based activated carbon. NH3 breakthrough column experiments show that the modification of the original activated carbon with nitric acid, that is, the incorporation of oxygen surface groups, highly improves the adsorption behavior at room temperature. Apparently, there is a linear relationship between the total adsorption capacity and the amount of the more acidic and less stable oxygen surface groups. Similar experiments using moist air clearly show that the effect of humidity highly depends on the surface chemistry of the carbon used. Moisture highly improves the adsorption behavior for samples with a low concentration of oxygen functionalities, probably due to the preferential adsorption of ammonia via dissolution into water. On the contrary, moisture exhibits a small effect on samples with a rich surface chemistry due to the preferential adsorption pathway via Brønsted and Lewis acid centers from the carbon surface. FTIR analyses of the exhausted oxidized samples confirm both the formation of NH4+ species interacting with the Brønsted acid sites, together with the presence of NH3 species coordinated, through the lone pair electron, to Lewis acid sites on the graphene layers.

Meeting minutes maintained by the Secretary, May 7, 1776; June 4, 1776; and July 2, 1776

Because the Secretary was absent from the May 7, 1776 meeting, John Winthrop was chosen as Secretary pro hac vice (for that occasion only). Samuel Cooke, Secretary pro tempore, recorded the minutes for the June 4, 1776 meeting, and the minutes from the July 2, 1776 meeting are in an unknown hand.

Meeting minutes maintained by the Secretary, Nov. 12, 1777

These minutes concern General William Heath's request for permission to house the soldiers of John Burgoyne – British prisoners of war – at Harvard. The Overseers voted to recommend that the Corporation allow the soldiers to occupy one or more College buildings, in spite of various hesitations. It has not been decisively determined whether or not the British troops were ultimately housed at Harvard. Some sources assert that no buildings were occupied, while others claim that Burgoyne and his soldiers lived in Apthorp House for a time.

Meeting minutes maintained by the Secretary, April 17, 1792 and May 7, 1793

These minutes, recorded on the recto and verso of a single page, are incomplete excerpts.