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  • 1
    Electronic Resource
    Electronic Resource
    Electron-Transfer Properties and Active-Site Structure of the Type 1 (Blue) Copper Protein Umecyanin (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 104-109 
    Details
    ISSN: 0947-6539
    Keywords: copper proteins ; cross-reactions ; electron-transfer reactions ; kinetics ; metalloproteins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron self-exchange rate constant for the Type 1 blue copper protein umecyanin from horseradish roots has been determined as 6.1 × 103 M-1 S-1 at pH 7.5, I = 0.100 M, 25°C by an NMR line-broadening method. The value obtained is one of the lower self-exchange rate constants determined for this class of protein; this is attributed to the presence of positively charged residues near to the electron-transfer site. The self-exchange rate constants calculated by means of a Marcus analysis of data for the cross-reactions (25°C) of umecyanin with azurin and cytochrome c551 (both from Pseudomonas aeruginosa) are substantially less at 8.0M-1 S-1 and 13.9M-1S-1, respectively, and are independent of pH in the range 7.0-8.0, I = 0.100M. The discrepancy between the self-exchange rate constants obtained by these two different methods can be rationalised if it is assumed that umecyanin reacts with the two proteins employed in the cross-reaction studies through the same site, but that this site is different from that used for the self-exchange process. A comparison of the primary structure of umecyanin with those of other Type 1 copper proteins has revealed that a glutamine rather than a methionine is likely as the fourth ligand of Cu at the active site. Other comparisons are made with stellacyanin, and the electron-transfer reactivity of the two proteins is discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.19960020118
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  • 2
    Electronic Resource
    Electronic Resource
    Structure, Properties and Reactivity of the FeIIFeIII and ZnIIFeIII Purple Acid Phosphatases (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 2105-2115 
    Details
    ISSN: 1434-1948
    Keywords: Metalloenzymes ; Purple Acid Phosphatases ; Phosphate Ester Hydrolysis ; Dinuclear metal active sites ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This microreview describes the structure, properties and mechanisms of the purple acid phosphatases (PAP). The enzyme is isolated from mammalian, plant and bacterial sources. X-ray structural information is now available for the enzyme from pig (uteroferrin), rat and kidney beans. Features of the mechanism are the concerted action of a labile MII centre (FeII or ZnII) alongside a more inert FeIII. The latter is effective as a conjugate-base FeOH2+, which initiates hydrolysis at the MII-bound phosphate ester by a process involving OH- replacement of OR- at the PV. Histidine residues near to the active site help bind the phosphate and are involved in the release of OR-. Effects of replacement of the FeII by MnII, CoII, NiII, CuII and ZnII, and of FeIII by GaIII,AlIII and InIII have been studied. The mechanistic role of the ZnIIZnII combination in alkaline phosphatases, and other related dinuclear centres is also considered.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Scanning probe microscope imaging of polyaniline thin films in non-contact mode (1994)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 21 (1994), S. 814-817 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The structure of electropolymerized thin films of polyaniline has been studied using the techniques of contact and non-contact scanning probe microscopy (SPM). Films exposed to Ir+ cations in solution, as well as unexposed films, were examined. Contact-mode SPM images of these films reveal only a diffuse, amorphous surface structure in both types of film, while non-contact SPM images indicate an intricate, nanometer-scale domain structure. Film growth is in a layer-by-layer mode, with each layer consisting of small polymer bundles of average dimension 1000 ± 75 Å. The Ir+ incorporation in these films does not involve a restructuring of the film morphology. The relevance of the microscopic domain structure to models describing conduction mechanisms in these films is also discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740211113
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