Multiple pathways of charge recombination revealed by the temperature dependence of electron transfer kinetics in cyanobacterial photosystem Iстатья

Статья опубликована в высокорейтинговом журнале

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Дата последнего поиска статьи во внешних источниках: 18 сентября 2019 г.

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[1] Multiple pathways of charge recombination revealed by the temperature dependence of electron transfer kinetics in cyanobacterial photosystem i / G. Milanovsky, O. Gopta, A. Petrova et al. // Biochimica et Biophysica Acta - Bioenergetics. — 2019. — Vol. 1860, no. 8. — P. 601–610. The kinetics of charge recombination in Photosystem I P700-FA/FBcomplexes and P700-FXcores lacking theterminal iron‑sulfur clusters were studied over a temperatures range of 310 K to 4.2 K. Analysis of the chargerecombination kinetics in this temperature range allowed the assignment of backward electron transfer from thedifferent electron acceptors to P700+. The kinetic and thermodynamic parameters of these recombination re-actions were determined. The kinetics of all electron transfer reactions were activation-less below 170 K, theglass transition temperature of the water-glycerol solution. Above this temperature, recombination from [FA/FB]−in P700-FA/FBcomplexes was found to proceed along two pathways with different activation energies (Ea).The charge recombination via A1Ahas an Eaof ∼290 meV and is dominant at temperatures above ∼280 K,whereas the direct recombination from FX−has an Eaof 22 meV and is prevalent in the 200 K to 270 K tem-perature range. Charge recombination from the FXcluster becomes highly heterogeneous at temperatures below200 K. The conformational mobility of Photosystem I was studied by molecular dynamics simulations. The FXcluster was found to‘swing’by ∼30o along the axis between the two sulfur atoms proximal to FA/FB. The partialrotation of FXis accompanied by significant changes of electric potential within the iron‑sulfur cluster, whichmay induce preferential electron localization at different atoms of the FXcluster. These effects may account forthe partial arrest of forward electron transfer and for the heterogeneity of charge recombination observed at theglass transition temperature. [ DOI ]

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