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Abstract

This report is devoted to the protolytic reactions which accompany electron abstraction from water and are expected to give a clue to the intermediate stages of stepwise catalysis. Broken chloroplasts from higher plants were studied. A spectrophotometric technique to measure proton release into the narrow (20 nm) inner phase of thylakoids was perfected for very high sensitivity (10**- 3 pH-units) at high time resolution (microseconds) and with regard to spatial resolution. Starting from the lowest oxidation state of the manganese protein a stoichiometric pattern of proton release per electron abstracted was observed. We furthermore determined the stoichiometry and the kinetics of proton release in the presence of hydroxylamine. Based on this information we define restrictions for possible mechanisms of water oxidation. However, the exact mechanism still remains obscure, mainly because of insufficient knowledge on the state of manganese in the enzyme. Further work will be directed to probe the enzyme with several different water analogues.

Additional information

Authors: JUNGE W, UNIVERSITAET OSNABRUECK (GERMANY);FORSTER V UNIVERSITAET OSNABRUECK (GERMANY), UNIVERSITAET OSNABRUECK (GERMANY)
Bibliographic Reference: EUR 9331 EN (1984) MF, 61 P., BFR 120, BLOW-UP COPY BFR 305, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
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