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  • Title: A time-resolved iron-specific X-ray absorption experiment yields no evidence for an Fe2+ --> Fe3+ transition during QA- --> QB electron transfer in the photosynthetic reaction center.
    Author: Hermes S, Bremm O, Garczarek F, Derrien V, Liebisch P, Loja P, Sebban P, Gerwert K, Haumann M.
    Journal: Biochemistry; 2006 Jan 17; 45(2):353-9. PubMed ID: 16401066.
    Abstract:
    Previous time-resolved FTIR measurements suggested the involvement of an intermediary component in the electron transfer step Q(A)- --> Q(B) in the photosynthetic reaction center (RC) from Rhodobacter sphaeroides [Remy and Gerwert (2003) Nat. Struct. Biol. 10, 637]. By a kinetic X-ray absorption experiment at the Fe K-edge we investigated whether oxidation occurs at the ferric non-heme iron located between the two quinones. In isolated reaction centers with a high content of functional Q(B), at a time resolution of 30 micros and at room temperature, no evidence for transient oxidation of Fe was obtained. However, small X-ray transients occurred, in a similar micro- to millisecond time range as in the IR experiments, which may point to changes in the Fe ligand environment due to the charges on Q(A)- and Q(B)-. In addition, VIS measurements agree with the IR data and do not exclude an intermediate in the Q(A)- --> Q(B) transition.
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