THE REDUCTIVE PHOTOALKYLATION OF FLAVIN BY N-ALLYLTHIOUREA |
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Authors: | Ulrich Ott Rainer Traber Peter Hemmerich Horst E A Kramer |
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Institution: | Institut für Physikalische Chemie der Universität Stuttgart, Pfaffenwaldring 55, D-7000 Stuttgart 80, W. Germany;Fakultät für Biologie der Universität Konstanz, Postfach 5560, D-7750 Konstanz I, W. Germany |
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Abstract: | Illumination of flavin in the presence of N-allythiourea (ATU) inhibits catalytic turnover of flavin between its reduced and oxidized redox states by adduct formation, the adduct being no longer reoxidisable by oxygen. The first step in the mechanism of adduct formation is an electron transfer from ATU to flavin in the photoexcited triplet state. In further steps, the ATU radical cation deprotonates, electronic rearrangement occurs and radical combination with the flavosemiquinone follows, yielding a cyclic product in which ATU is added in the 4a- and 5-position to the flavin chromophore. Reaction rates and yields were determined by flash photolysis and continuous illumination. A photochemical study by variation of the molecular structure of ATU was undertaken to prove the proposed mechanism and to determine the structural requirements of flavin inactivators. |
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