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  • 1
    ISSN: 1434-4475
    Keywords: Nonaqueous electron transfer ; Iron(III)trimethylphosphate complexes ; Ligand exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wurde die Kinetik der Outer-sphere Oxidation einer Reihe von Fe(Xphen) 3 2+ Ionen (X=H oder verschiedene Methylsubstituenten) mit Eisen(III), eingeführt als Fe(tmp)6(ClO4)3 (tmp=Trimethylphosphat), bei 25°C in Acetonitril (MeCN) untersucht. Diese Reaktionen sind sehr komplex, da gebundenestmp teilweise durchMeCN ausgetauscht wird, wobei der Ersatz einestmp-Moleküls durchMeCN das Redoxpotential um 0.2 V verschiebt. Deshalb sind die verschiedenen Solvatkomplexe in ihrer Reaktivität sehr unterschiedlich. Ein zweites wesentliches Merkmal der untersuchten Reaktionen ist der hohe Ladungstyp von +2/+3. Das bringt eine starke Erhöhung der Reaktionsgeschwindigkeit durch Elektrolytzusatz infolge von Ionenassoziation mit sich, die die Coulombsche Arbeit für die Bildung des Precursorkomplexes reduziert. Die Aufgabe bestand demnach in der Aufklärung von zwei Speziationsarten, der Solvations- und Ionenassoziationsgleichgewichte. Die Analyse weist auf das gleichzeitige Vorliegen von fünf Fe(tmp) n 3+ Species (n=2–6) hin, wobei vier von ihnen (n=2–5) reagieren. Zusätzlich gibt es für jedesn noch Ionenpaare und Ionentriplets mit Perchlorat. Eine zusätzliche Komplizierung ergibt sich, weil bestimmte Solvationsgleichgewichte nicht immer schnell sind im Vergleich zu den Redoxreaktionen, die dann nicht mehr pseudo-erster-Ordnung sind. Wenn auch die Geschwindigkeitskonstanten nicht mit der üblicherweise gewünschten Präzision angegeben werden können, sind zumindest zwei Ergebnisse nennenswert: (a) Es wird die relative Bedeutung der driving force und der Reaktantenladung für die Gesamtreaktivität hervorgehoben und (b) Je stärker die Reduktionskraft des Fe(Xphen) 3 2+ Ions, desto weniger kann es die verschiedenen Solvatspezies unterscheiden (Reaktivitäts-Selektivitäts-Beziehung).
    Notes: Summary The kinetics of outer-sphere oxidation of Fe(Xphen) 3 2+ ions (X=H or several methyl substituents) in acetonitrile (MeCN) solution by iron(III), introduced as Fe(tmp)6(ClO4)3 (tmp=trimethylphosphate), have been investigated at 25°C. The reactions are very complex because of solvation equilibria betweentmp andMeCN coordinated at Fe3+, with a reduction potential difference of 0.20 V for the replacement of onetmp byMeCN. This makes the various solvate species highly different in driving force. The second essential feature is the high charge-type of +2/+3. This brings about strong acceleration by salt because of ion association reducing the work necessary to overcome the Coulombic repulsion in forming the precursor complex. The task was to deconvolute two kinds of speciation: the ionic and the solvate speciations. The analysis suggests the concurrent existence of five Fe(tmp) n 3+ (n=2–6) species among which four species (n=2–5) are reacting, with an additional mono and bis perchlorate ion pair for eachn. Extra complications arise as some of the solvation equilibria are not always fast compared to the redox reactions, leading to non-first order rate constants. Although the rate constants could not be defined with the desired precision, at least two results are worth noting: (i) The relative effects of driving force and charge are highlighted in controlling overall reactivity. (ii) The stronger the reducing power of the Fe(Xphen) 3 2+ moiety, the less it can distinguish between the various solvate species (reactivity-selectivity relationship).
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 9 (1993), S. 243-247 
    ISSN: 1573-0972
    Keywords: Bacterial immobilized cells ; liquid-drying ; preservation ; microbial biosensors ; xenobiotics detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A simple and effective method for the drying of immobilized bacterial cells to be used directly in a microbial biosensor for measurement of activity is reported. As a case example, plasmid-bearing cells of Alcaligenes eutrophus JMP 134, DSM 4058 were immobilized on various carriers and liquid-dried. The dried cell-matrix was used directly after rehydration/reactivation as the biological component of a biosensor for determining the concentration of xenobiotic compounds in the environment. Good viability results were obtained after long-term storage and cells exhibited no loss of plasmids responsible for the 2,4-dichlorophenoxyacetic acid (2,4-D) degradation. The activity of the cells for 2,4-D was proved using a respiration electrode. No time-consuming, repeated cell cultivation and harvesting was required, as the cells preserved from a single batch served as a continuous source for activity measurements. Many other microbial cultures can be preserved by this method and the cells preserved in the form of immobilized dried cell-matrix can be used directly to perform enzymatic tests, complex biochemical conversions and for production in the reactors. The dried cell-matrix can serve as a stable interchangeable component for a multipurpose biosensor.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 1287-1292 
    ISSN: 0006-3592
    Keywords: integrated optics ; grating coupler ; FIA ; on-line monitoring ; animal cell culture ; monoclonal antibody ; immunochemical sensor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A grating coupler was used for the on-line determination of monoclonal antibodies produced in perfused animal cell bioreactor. The device was connected with the culture vessel via a flow-injection analysis (FIA) system, which was controlled automatically. Specific antimouse lgG antibodies were immobilized on the surface of the sensor-chip. After injection of the sample, the binding of mouse lgG was observed in real time. The regeneration of the binding sites of the immobilized antibodies using an acidic solution allowed the on-line detection of produced monoclonal antibodies in the range of 10 to 150 μg/mL. In contrast to other techniques coupled to bioprocesses, the developed method represents a regenerable direct immunosensor. Results were compared with standard ELISA techniques (off-line) and a competitive immunochemical assay using the grating coupler (off-line). © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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