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    Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis.

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    Authors
    Land, Edward J
    Ramsden, Christopher A
    Riley, Patrick A
    Affiliation
    CRC Drug Development Group, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester M20 4BX, UK. eland@mighty-micro.co.uk
    Issue Date
    2001-11-15
    
    Metadata
    Show full item record
    Abstract
    The contributions of pulse radiolysis towards characterisation of unstable ortho-quinones relevant to melanogenesis are reviewed. The quinones discussed include dopaquinone, the precursor of both eumelanogenesis and phaeomelanogenesis, and 5-S-cysteinyldopaquinone, an early component of the phaeomelanogenic pathway. Redox exchange between dopaquinone and 5-S-cysteinyldopa is shown to be a determinant of the balance between eumelanogenesis and phaeomelanogenesis. Ortho-quinones resulting from the oxidation of tertiary N,N-dialkylcatecholamines cyclise to redox-inactive betaines which fail to autoactivate tyrosinase. This is consistent with the dopa detected during melanogenesis catalysed by tyrosinase being formed indirectly by a combination of dopaquinone intramolecular reductive addition to form leucodopachrome (cyclodopa), followed by redox exchange between remaining dopaquinone and leucodopachrome. Rapid tautomerism of the ortho-quinone of 4-cyanomethylcatechol to a redox-inactive quinomethane likewise inhibits tyrosinase autoactivation. The incorporation of trihydric phenol moieties in melanin is modelled by the reactions of several ortho-quinones with phloroglucinol, which itself is not directly oxidised by tyrosinase due to the meta-positioning of the hydroxyl groups. The importance of a susceptibility towards nucleophilic attack as well as a propensity to undergo redox-exchange, in the chemistry of melanogenic ortho-quinones, is emphasised.
    Citation
    Pulse radiolysis studies of ortho-quinone chemistry relevant to melanogenesis. 2001, 64 (2-3):123-35 J. Photochem. Photobiol. B, Biol.
    Journal
    Journal of Photochemistry and Photobiology. B, Biology
    URI
    http://hdl.handle.net/10541/85735
    PubMed ID
    11744399
    Type
    Article
    Language
    en
    ISSN
    1011-1344
    Collections
    All Paterson Institute for Cancer Research

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