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  • Polymer and Materials Science  (3)
  • Carbohydrate-binding proteins (lectins)  (2)
  • Target-directed drug synthesis  (1)
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  • 1
    ISSN: 1432-0878
    Keywords: Carbohydrate-binding proteins (lectins) ; Tumor ; Metastasis ; Sarcoma virus ; Virus-induced transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A tumor model system of clones of myeloproliferative sarcoma virus (MPV)-transformed rat fibroblasts (NRK) with different growth properties and metastatic potential was studied. The relationship between metastatic behavior and composition of carbohydrate-binding proteins (lectins) was analyzed by affinity chromatography. The metastatic variant differs qualitatively from its parental clone in the presence of galactoside-binding proteins at apparent molecular weights of 80 kDa, 70 kDa, 22 kDa, 18 kDa and 16 kDa and of a fucose-binding protein at apparent molecular weight of 42 kDa. The α-glucosyl-binding proteins at apparent molecular weights of 67 kDa and 53 kDa and a galactoside-binding protein of apparent molecular weight of 34 kDa, however, are not detectable in the metastatic variant in comparison to its parental clone. In this respect the parental clone shows closer resemblance to the clone 5–8#1 with different growth properties and low metastatic potential than to its own metastatic variant. Furthermore, only the parental clone has a melibiose- and a mannan-binding protein of an apparent molecular weight of 64 kDa and 14 kDa, respectively. Rosette formation as model system for intercellular interaction reveals differences in the inhibition pattern with sugar between the two clones 5–8#1 and 5–20#20, whereas the metastatic variant 5–20#20 (s) exhibits drastically reduced capability to form rosettes. Initial experiments demonstrate the feasibility of drug targeting to transformed fibroblasts via carbohydrate-binding proteins.
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  • 2
    ISSN: 1432-0878
    Keywords: Carbohydrate-binding proteins (lectins) ; Tumor ; Fibroblasts ; Sarcoma virus ; Virus-induced reactions ; Transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Three clones of myeloproliferative virus (MPV)-transformed rat fibroblasts (NRK) with different growth properties and morphology were transplanted to athymic nude mice. Presence of carbohydrate-binding proteins was inferred by fluorescence microscopy using fluorescent, glycosylated markers. Salt and detergent extracts of tumors from this model system were fractionated under identical conditions on different sets of Sepharose columns, to which lactose, asialofetuin, melibiose, mannan and fucose had been covalently linked. Successive elution by chelating reagent and specific sugar resulted in isolation of the different Ca2+-dependent and Ca2+-independent endogenous carbohydrate-binding proteins that were assayable as agglutinins. In comparison, the different tumors displayed a pattern with qualitative and quantitative alterations. Since protein-carbohydrate interaction mediated by carbohydrate-binding proteins (lectins) is of importance for cognitive processes, it is remarkable that the pattern of membrane glycoproteins, isolated by affinity chromatography on resins with immobilized plant lectins, had also been found to reveal certain individual properties for receptors specific for peanut agglutinin (PNA) and Ulex europaeus agglutinin (UEA). These demonstrated differences within the system of protein-carbohydrate interaction suggest that endogenous lectins and their ligands have potential significance as markers defining a certain phenotype within this tumor model system.
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  • 3
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hexanucleotide Gm-A-A-Y-A-ψp excised from the anticodon loop of yeast tRNAPhe and its constituent oligonucleotides have been studied by ultraviolet absorption spectroscopy, static fluorescence, and circular dichroism. Gm-Ap has a melting point of 45°C and a high melting enthalpy when compared with G-Ap; hence 2′-O-methylation seems to stabilize stacking interactions. The nucleobase Y adjacent to the 3′-side of the anticodon triplet interacts stronger with its 3′-neighboring A than with its 5′-neighboring A. It is concluded that the base Y disconnects the stack of the anticodon itself from the stack of the anticodon stem, thereby setting a reading frame for the mRNA in the course of protein biosynthesis. From the opposite signs of the short-wavelength Cotton effects in the spectra of Gm-A-A-Y-Ap and Gm-A-A-Y, it is concluded that Y after removal of its 3′ neighbor undergoes a dramatic change in its conformation. The fluorescence of the nucleobase Y upon addition of Mg2+ is enhanced in oligonucleotides longer than two. An identical enhancement is observed for tRNAPhe, indicating that this Mg2+ effect is a property of an oligonucleotide segment and does not reflect conformational changes of the whole tRNA. The data presented here reveal that the basic structural features of the anticodon loop are already present in the hexanucleotide Gm-A-A-Y-A-ψp and are not determined by the overall structure of tRNA.
    Additional Material: 9 Ill.
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  • 4
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A macroporous nonswellable copolymer of styrene and divinylbenzene (I) is converted to the polymeric derivative of p-anisyldiphenylmethyl chloride (VI) which reacts with the nucleosides dT(Ac) (VIIa), dbz6A(Ac) (VIIb) and the dinucleoside monophosphate dT-dT(Ac) (X) to form an ether bond. The rate of the cleavage of nucleotidic material from the carrier is studied as function of the kind of the protected or unprotected nucleoside or dinucleoside monophosphate, of the relation of VI to X in the loading reaction of the carrier and as a function of temperature. In order to enable comparable experiments in this heterogeneous reactions two values are introduced: the relative initial rate vrela which mainly describes the hydrolysis of the p-anisyldiphenylmethyl ether bond and the relative rate after one hour vrel1h which describes the diffusion phenomena taking place in the highly porous polymer.
    Notes: Ein makroporöses unquellbares Styrol-Divinylbenzol-Copolymerisat (I) wird in ein polymeres Derivat des p-Anisyldiphenylmethylchlorids (VI) übergeführt, das mit den Nucleosiden dT(Ac) (VIIa), dbz6A(Ac) (VIIb) und dem Dinucleosidmonophosphat dT-dT(Ac) (X) veräthert wird. Die Abspaltungsgeschwindigkeit von nucleotidischem Material vom Träger wird in Abhängigkeit von der Art des geschützten oder ungeschützten Nucleosids bzw. Dinucleosidphosphats, von dem bei der Beladung des Trägers vorliegen den Verhältnis von VI zu X und in Abhängigkeit von der Temperatur untersucht. Um vergleichende Untersuchungen dieser heterogenen Reaktionen durchführen zu können, werden zwei Größen eingeführt: die relative Anfangsgeschwindigkeit vrela beschreibt vorwiegend die Hydrolyse der p-Anisyldiphenylmethyläther-Bindung, die relative Geschwindigkeit nach einer Stunde vrel1h das komplexe Diffusionsgeschehen innerhalb des verzweigten Hohlraumsystems des Polymerisates.
    Additional Material: 3 Tab.
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  • 5
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ultraviolet absorption and static fluorescence properties of hexanucleotide (Gm-A-A-Y-A-ψp) and a dodecanucleotide (A-Cm-U-Gm-A-A-Y-A-ψ-m5C-U-Gp) excised from the anticodon region of phenylalanine tRNA from yeast have been studied with respect to temperature, pH, ionic strength, and Mg2+ concentration. At low temperature these oligomers have a largely stacked structure. Only the melting data of the dodecanucleotide in absence of Mg2+ fit a two-state model. From the different melting behavior of the oligonucleotides after excision of base Y, a rodlike structure of the hexanucleotide produced by stacking interactions can be concluded. The Y fluorescence increase produced by Mg2+ has been used to evaluate the binding equilibria between Mg2+ and the oligonucleotides. One strong binding site per oligonucleotide and a greater number of weak binding sites have been found. The fluorescence of the free base Y is not influenced by Mg2+. The dodecanucleotide enhances the ethidium fluorescence to the same extent as tRNAPhe and produces comparable shifts in the excitation and emission spectra. Therefore a double helical structure for this oligomer under the assay conditions is suggested. Only weak binding of ethidium to the hexanucleotide is observed, indicating that intercalation of the dye into its structure is not favored. The data show the decisive role of the nucleobase Y in maintaining a rigid stacked structure of the anticodon nucleotides. This structure is stabilized by high ionic strength, Mg2+, and ethidium.
    Additional Material: 10 Ill.
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  • 6
    ISSN: 0570-0833
    Keywords: Target-directed drug synthesis ; Aminoacyl-tRNA synthetases ; Protein biosynthesis ; Enzymes ; Drug research ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The “tailor-made” pharmaceutical has been an old dream ever since Paracelsus' days. His saying “Dosis sola facit venenum” is still valid. The ideal pharmacon should inhibit the pathological process or the parasitical organism to a maximum while causing as little harm as possible to the human organism. In order to achieve this goal one must try to make use of metabolic differences between the metabolism of the pathological organism and normal human metabolism in a rational way. With today's improved knowledge of enzymatic processes this seems to be a possible and highly promising approach. The pharmaceutical should act upon a process of central importance, such as the process of protein biosynthesis, where the required highly accurate construction of the macromolecules is achieved by a “proofreading” process. It is shown that this “proofreading” mechanism exhibits specific difference in different species.
    Additional Material: 2 Ill.
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