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  • Analytical Chemistry and Spectroscopy  (8)
  • General Chemistry  (4)
  • IAPS-forskolin  (2)
  • 1
    ISSN: 1432-1912
    Keywords: Glucose transport ; IAPS-forskolin ; Insulin-regulated glucose transporter GLUT4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two arginine residues (RR333/334) in the conserved GRR motif located in the endofacial loop between helix 8 and 9 of the glucose transporter GLUT4 were substituted for leucine and alanine, respectively. Reconstituted glucose transport activity of the construct (GLUT4-RR333/4LA) expressed in COS-7 or LM(TK-) cells was less than 10% of that of the wild-type GLUT4. In contrast, binding of the inhibitory ligand cytochalasin B and glucose-inhibitable photolabeling with IAPS-forskolin were not significantly affected. Exchange of a histidine residue (H337Q) previously believed to be involved in the binding of inhibitory ligands failed to affect any of the investigated parameters. These data suggest that positive charges in the GRR motif at the cytoplasmic surface of the transporter participate in the conformational changes of the carrier protein during the process of facilitated diffusion.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1912
    Keywords: Key words Glucose transport ; IAPS-forskolin ; Insulin-regulated glucose transporter GLUT4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Two arginine residues (RR333/334) in the conserved GRR motif located in the endofacial loop between helix 8 and 9 of the glucose transporter GLUT4 were substituted for leucine and alanine, respectively. Reconstituted glucose transport activity of the construct (GLUT4-RR333/4LA) expressed in COS-7 or LM(TK–) cells was less than 10% of that of the wild-type GLUT4. In contrast, binding of the inhibitory ligand cytochalasin B and glucose-inhibitable photolabeling with IAPS-forskolin were not significantly affected. Exchange of a histidine residue (H337Q) previously believed to be involved in the binding of inhibitory ligands failed to affect any of the investigated parameters. These data suggest that positive charges in the GRR motif at the cytoplasmic surface of the transporter participate in the conformational changes of the carrier protein during the process of facilitated diffusion.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 461-469 
    ISSN: 1040-7685
    Keywords: mass spectrometry ; on-line capillary electrophoresis ; MS / MS analysis ; sheathless electrospray source ; peptides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sensitivity that can be obtained with the quadrupole ion trap for on-line CE analysis using a sheathless electrospray interface and gold-tipped columns is examined. Capillaries of different i.d. are compared in continuous infusion experiments and the effects of sheath solvents on the signal for some peptides and proteins are illustrated. The sheathless CE/ITMS system using 20 μm i.d. columns is shown to provide mid-attomole detection levels for leucine enkephalin in total ion electropherograms under full scan conditions. Good quality MS/MS spectra are also obtained for low femtomole injections of this peptide.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 439-442 
    ISSN: 0935-6304
    Keywords: Electrokinetic chromatography (EKC) ; Pseudo-stationary phase ; Electroosmotic flow ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new mass spectrometry technique using an inductively coupled plasma (ICP) ionization source and an ion-trap mass spectrometer (ITMS) detector is described and evaluated for elemental and isotopic analysis. Initial results obtained with the ICP-ITMS technique include sub-ppb detection of bare ions for, most elements, complete destruction of typical polyatomic matrix ions (e.g., CIO+, ArO+, and ArCl+), and effective neutralization of strong Ar+ ion currents. The latter effects allow observation of clearer mass spectra at m/z 〈 80 and potentially improved detection of ‘problem’ elements in ICP-MS (e.g., K, Ca, V, Fe, As, and Se). Formation of poly-oxide and -hydroxide ions of metals with high oxide bond strengths were observed and require system modifications to alleviate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 1222-1229 
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Tandem mass spectra of a variety of adenine-containing deoxynucleic acid anions obtained using collisional activation in a quadrupole ion trap are described. Data are reported for singly charged mono-, di- and trinucleotide species, and also for multiply charged anions derived from tri-, tetra-, penta- and hexanucleotides. Attention is focused on the first step in the unimolecular decomposition of these species, namely the loss of the nucleobase. Specifically, the competition between the loss of the nucleobase as a neutral versus its loss as an anion is addressed within the context of a proposed proton-bound intermediate consisting of the nucleobase and a phosphodiester linkage. The data are interpreted on the basis of the energy surface involved in the break-up of the proton-bound intermediate, which can explain why the competition between loss of a neutral versus charged base is strongly dependent upon the charge of the parent ion.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 470-478 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The scan modes that can be used to obtain daughter ion, parent ion, and constant neutral-loss spectra on hybrid mass spectrometers are derived for instruments with a quadrupole combined with a magnetic and/or electric sector. All combinations of sector/quadrupole and quadrupole/sector instruments are discussed. The advantages or lack thereof of the various scans are presented with respect to operation, resolution and potential artifacts.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 22 (1987), S. 224-228 
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An abundant loss of hydroxyl in decompositions of ortho-substituted nitroarene cations is commonly observed when the substituent contains one or more labile hydrogen atoms. The major loss of hydroxyl also takes place from many but not all of the corresponding molecular anions. Data are reported for the collisionally activated decompositions of the cations and anions of o-nitrotoiuene, o-nitrophenol and o-nitroaniline. Data for some dinitro ions are also reported. The results can be rationalized on the basis of a greater degree of charge developed at the substituent in the transition state of the anions that leads to a rearranged ion. It is from this structure tint hydroxyl is lost via simple bond cleavage. This can be viewed most simply as a proton transfer from the substituent to the nitro group in the anion as opposed to hydrogen transfer in the analogous step for the cation. The degree to which hydroxyl loss occurs is therefore largely determined by the tendency for hydrogen (cations), or proton (anions), transfer from the substituent to the nitro group.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Als Höhepunkte auf dem Gebiet der Organoelementchemie der schwereren Elemente der vierten Hauptgruppe (Gruppe 14 des Periodensystems) in den 80er Jahren gelten die Darstellung und vollständige Charakterisierung dreier Verbindungsklassen, deren Existenz bis dahin aufgrund ihrer Reaktivität für nicht möglich gehalten wurde. Hierbei handelt es sich um 1) die dreigliedrigen Ringsysteme Cyclotrisilan, -trigerman und -tristannan, 2) Moleküle mit Element-Element-Doppelbindungen einschließlich Disilen, Digermen und Distannen sowie 3) gespannte Polycyclen mit einem Gerüst aus den schwereren Elementen der 4. Hauptgruppe, z. B. Bicyclo[1.1.0]tetrasilan, Hexagermaprisman und Octasilacuban. Die meisten dieser Verbindungen sind durch sperrige Substituenten stabilisiert. Die Verbindungen ermöglichten Untersuchungen über die Veränderungen physikalischer und chemischer Eigenschaften in Abhängigkeit vom Element und den Substituenten sowie über die thermische und photochemische Reaktivität dieser Systeme, wobei zweiwertige Carben-Analoga nachgewiesen wurden. Parallel zu den experimentellen Arbeiten wurden an nahezu allen im Beitrag diskutierten Stammverbindungen Rechnungen durchgeführt. Einige Polycyclen weisen den Weg zu Verbindungen mit einer Element-Element-Dreifachbindung.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Diese Übersicht stellt neuere experimentelle Ergebnisse der Erforschung der unendlichen Geschichte der Vitamin-B12-Biosynthese vor, wobei hauptsächlich auf Arbeiten aus der Arbeitsgruppe des Autors zurückgegriffen wird. Darüber hinaus gibt sie einen persönlichen Ausblick auf die Zukunft der Naturstoff-Biosyntheseforschung. Von zentraler Bedeutung ist mittlerweile die leistungsfähige Kombination von molekularbiologischen und modernsten spektroskopischen Techniken. Jene dienen der Suche nach und der Expression von Genen, die für die Enzyme der Biosynthese codieren, diese machen die biochemischen Vorgänge im NMR-Röhrchen direkt beobachtbar. Als logische Weiterentwicklung dieser Ansätze wird die Durchführbarkeit der Eintopf-Multienzymsynthese von Naturstoffen vorgestellt. Dank der Entwicklung und Nutzung von Klonierungstechniken und der daraus resultierenden Verfügbarkeit von Enzymen für die C-C-Verknüpfung hat sich ein grundlegender Wandel im “Handwerkszeug“ des Bioorganikers vollzogen. Gleichzeitig seien aber auch die Organiker angesprochen, die sich diesen technischen Fortschritt zunutze machen wollen. Ihnen wird sich eine neue Welt natürlicher Katalysatoren erschließen, die Synthesen mit hohen Ausbeuten bei einem oftmals überraschenden, aber durchaus willkommenen Mangel an Substratspezifität versprechen. Und schließlich hoffen wir, unsere Begeisterung für diese modernen Methoden weiterzugeben, mit denen heutige wie auch künftige Generationen von Chemikern die Synthesewege der Natur zu komplexen Naturstoffen erforschen können.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
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