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  • 1
    ISSN: 1573-4919
    Keywords: transcription ; RNA polymerase III ; casein kinase II ; CK2 ; TATA binding protein ; TFIIIB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We have investigated the molecular basis of the requirement for protein kinase CK2 in nuclear transcription in Saccharomyces cerevisiae. In vivo and in vitro analysis has demonstrated that CK2 is required for efficient transcription of the tRNA and 55 rRNA genes by RNA polymerase III. This suggests that a component of the pol III transcription machinery is regulated by CK2. We tested this possibility by a biochemical complementation approach in which components of the pol III transcription machinery from wild type cells were tested for their ability to rescue transcription in extract from a conditionally CK2-deficient mutant. We found that pol III transcription initiation factor IIIB (TFIIIB) fully restores transcription in CK2-deficient extract. Further in vitro studies revealed that TFIIIB must be phosphorylated to be active, that a single subunit of wild type TFIIIB, the TATA binding protein (TBP), is efficiently phosphorylated by CK2, and that recombinant TBP and a limiting amount of CK2 rescues transcription in CK2-deficient extract. We conclude that TBP is the physiological target of CK2 among the components of the pol III transcription machinery. The implications of this result are discussed in the context of previous data concerning the regulation of TFIIIB.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units of Oligosaccharides, LXVI.  -  Synthesis of O-Glycopeptide Blocks of GlycophorineA block synthesis to O-glycopeptides can be realized by reaction of the disaccharide halide 10 with either L-serine- or L-threonine-containing peptide derivatives. Thus, the reaction of 10 with 8 yields stereoselectively the L-Ser-L-Ser derivative 15 in which two disaccharide residues are α-glycosidically linked to the peptide. However, this method is limited by the low solubilities of peptide derivatives in dichloromethane. A more general procedure represents the step-by-step synthesis of O-glycopeptides in which selectively deblocked derivatives of disaccharide amino acids are combined by using the methods of peptide syntheses. An example is the reaction of 25 with 29 in the presence of EEDQ yielding the glycopeptide 30. The reagent potassium cyanide in methanol/ethanol proved to be the most suitable deacylation reagent for the deblocking of the saccharide units in the last step. The benzoyl groups can be removed without β-elimination or racemization of the peptide part.
    Notes: Eine Blocksynthese zu O-Glycopeptiden ist durch Umsetzung des Disaccharidhalogenides 10 mit L-Serin- oder L-Threonin-haltigen Peptid-Derivaten möglich. So ergibt die Umsetzung von 10 mit 8 stereoselektiv das L-Ser-L-Ser-Derivat 15, an das α-glycosidisch zwei Disaccharid-Reste geknüpft sind. Diese Methode wird jedoch durch geringe Löslichkeiten von Peptid-Derivaten in Dichlormethan begrenzt. Universeller anwendbar ist eine stufenweise Synthese von O-Glycopeptiden, bei der selektiv entblockierte Derivate von Disaccharid-Aminosäuren nach den Methoden der Peptidchemie verknüpft werden. So ergibt die Reaktion von 25 mit 29 in Gegenwart von EEDQ das Glycopeptid 30. Als bestes Entacylierungs-Reagenz für die Deblockierung der Saccharid-Einheiten im letzten Schritt hat sich Kaliumcyanid/Methanol/Ethanol bewährt. Hiermit erfolgt auch Abspaltung der Benzoylgruppen ohne β-Eliminierung oder Racemisierung des Peptidteiles.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1435-1447 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Building Units of Oligosaccharides, LXXIII. - Synthesis of the Tetrapeptide Sequence 12 to 15 of Asialoglycophorin A with Four Disaccharide Side ChainsThe protected O-glycosylated derivative of L-serine 2 and the homologous L-threonine compound 8, both with the Fmoc-group at the N-terminus and the benzyl ester at the C-terminus, can be used successfully in the synthesis of O-glycopeptides. In these compounds, it is possible to deblock the N-terminus or the C-terminus selectively. Beginning at the carboxyl end and with help of the peptide reagent EEDQ, these derivatives were used in a step by step synthesis of the glycosylated tetrapeptide 19. This structure with four disaccharide units of β-D-Gal-(1→3)-α-D-GalNAc represents the sequence 12 to 15 of the asialoglycophorin A.
    Notes: Das blockierte O-Glycosylserin-Derivat β-D-Gal-(1→3)-α-D-GalNAc-L-Ser 2 mit N-terminaler Fmoc-Gruppe und C-terminalen Benzylester sowie die entsprechende L-Threonin-verbindung 8 bieten einen allgemeinen Zugang zu O-Glycopeptiden. In ihnen läßt sich selektiv der N- oder C-Terminus freilegen. Beginnend am C-terminalen Ende wurde hiermit stufenweise unter Kondensationshilfe von EEDQ das Tetraglycopeptid 19 mit vier Disaccharideinheiten β-D-Gal-(1→3)-α-D-GalNAc synthetisiert. Es handelt sich hierbei um die Sequenz 12 bis 15 des Asialoglycophorin A.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 393-395 
    ISSN: 0170-2041
    Keywords: Glucuronidation ; Invertomers ; Esterase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of a Metabolite of Ciamexon Conjugated with D-Glucuronic AcidReaction of the alcohol 2 with the glucuronic acid derivative 6 in the presence of Ag triflate yields the protected β-D-glucuronide 8 by rearrangement of the orthoester 7. After deacetylation and saponification with pig liver esterase, the deblocked glucuronide 3 can be isolated. Due to the aziridine ring the glucuronic acid derivatives of 2 consist of a mixture of invertomers, as shown by 1H-NMR spectroscopy.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Unusual Reaction to Glycosyl Urethanes During a Synthesis of GlycopeptidesReaction of the disaccharide halide 1 with N-(3,5-dimethoxy-α,α-dimethylbenzyloxycarbonyl)-L-serine benzyl ester (5) unexpectedly yields the glycosyl urethane 10. Glycosidation of 5 predominantly occurs at the urethane oxygen and not at the free hydroxy group of L-serine. During the formation of 10 the β-hydroxy group of serine is converted into a 3,5-dimethoxy-α,α-dimethylbenzyl ether.
    Notes: Die Umsetzung des Disaccharidhalogenids 1 mit N-(3,5-Dimethoxy-α,α-dimethylbenzyloxycarbonyl)-L- serin-benzylester (5) führt unerwartet zum Glycosylurethan 10. Im Derivat 5 wird bevorzugt der Urethansauerstoff und nicht die freie OH-Gruppe des L-Serins glycosidiert. Während der Reaktion zu 10 erfolgt Überführung der β-OH-Gruppe des Serins in einen (3,5-Dimethoxy-α,α-dimethylbenzyl)ether.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0170-2041
    Keywords: Fructose 1,6-diphosphate ; (+)-exo-Brevicomin ; Aldol reaction, enzymatic ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemoenzymatic “Chiral-Pool” Synthesis of (+)-exo-Brevicomin from Carbohydrates Using Fructose 1,6-Diphosphate AldolaseFructose-1,6-diphosphate aldolase (EC 4.1.2.13) catalyzes the stereospecific aldol reaction between 1,3-dihydroxyacetone phosphate (4) and 5-oxohexanal (3) or its 5-dithiane-protected analog 8. The products of the aldol reactions are dephosphorylated with acid phosphatase (EC 3.1.3.2). Whereas the aldol adduct of 3 cyclizes spontaneously to give the bicyclic brevicomin precursor 3, the adduct of 8 first has to be deprotected with sulfuryl chloride and wet silica gel. The resulting bicyclic α-hydroxy ketone 3 is reduced with LiAlH4 to form the 1,2-diol 14 which is then deoxygenated to give the vinyl compound 17 by treatment of the corresponding dixanthate 15 with tributyltin hydride or by treatment of the corresponding mesylate 16 with sodium naphthalenide. The olefin 17 is finally converted to (+)-exo-brevicomin (1) by hydrogenation with diimide.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The structure and secretory activity of the accessory salivary gland in two species of Conus were examined using routine and histochemical techniques of light, scanning and transmission electron microscopy.The composite layers of the accessory salivary gland of Conus are a luminal epithelium, fibromuscular layer, submuscular layer, and a capsule. In C. flavidus and C. vexillum, the luminal epithelium is formed by epitheliocytes and cytoplasmic processes extending from the secretory cells, whose perikarya form the submuscular layer. The processes carry secretory cell products (chiefly Golgi-derived glycoprotein) across the fibromuscular layer and terminate between epitheliocytes (at the bases of the secretory canaliculi) or beyond the surface of the epithelial cells. Conus vexillum is distinguished from C. flavidus by its high content of lipofuscin. Epitheliocytes are the only microvillated cells in the accessory salivary gland of Conus. In C. flavidus, epitheliocytes extrude secretory granules, various types of cytoplasmic blebs and clear vesicles by apocrine “pinching off”. Clear vesicles are shed from the tips of microvilli. The luminal epithelial cells of C. vexillum similarly egest clear vesicles, but normally undergo additional holocrine secretion to release lipofuscin.The secretions of epitheliocytes appear to be major products of the accessory salivary gland: consideration of secretory activities by both epitheliocytes and secretory cells will therefore be necessary when directly investigating accessory salivary gland function in Conus.
    Additional Material: 35 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2024-01-30
    Description: Industrial contaminants accumulated in Arctic permafrost regions have been largely neglected in existing climate impact analyses. Here we identify about 4500 industrial sites where potentially hazardous substances are actively handled or stored in the permafrost-dominated regions of the Arctic. Furthermore, we estimate that between 13,000 and 20,000 contaminated sites are related to these industrial sites. Ongoing climate warming will increase the risk of contamination and mobilization of toxic substances since about 1100 industrial sites and 3500 to 5200 contaminated sites located in regions of stable permafrost will start to thaw before the end of this century. This poses a serious environmental threat, which is exacerbated by climate change in the near future. To avoid future environmental hazards, reliable long-term planning strategies for industrial and contaminated sites are needed that take into account the impacts of cimate change.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 9
    Publication Date: 2014-10-01
    Print ISSN: 1070-6631
    Electronic ISSN: 1089-7666
    Topics: Physics
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  • 10
    Publication Date: 2020-07-01
    Description: Air travel appears as particularly hazardous in a pandemic situation, since infected people can travel worldwide and could cause new breakouts in remote locations. The confined space conditions in the aircraft cabin necessitate a small physical distance between passengers and hence may boost virus transmissions. In our contribution, we implemented a transmission model in a virtual aircraft environment to evaluate the individual interactions between passengers during aircraft boarding and deboarding. Since no data for the transmission is currently available, we reasonably calibrated our model using a sample case from 2003. The simulation results show that standard boarding procedures create a substantial number of possible transmissions if a contagious passenger is present. The introduction of physical distances between passengers decreases the number of possible transmissions by approx. 75% for random boarding sequences, and could further decreased by more strict reduction of hand luggage items (less time for storage, compartment space is always available). If a second door is used for boarding and deboarding, the standard boarding times could be reached. Individual boarding strategies (by seat) could reduce the transmission potential to a minimum, but demand for complex pre-sorting of passengers. Our results also exhibit that deboarding consists of the highest transmission potential and only minor benefits from distance rules and hand luggage regulations.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
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