Abstract
We establish a general kinetic scheme for the energy transfer and radical-pair dynamics in photosystem I (PSI) of Chlamydomonas reinhardtii, Synechocystis PCC6803, Thermosynechococcus elongatus and Spirulina platensis grown under white-light conditions. With the help of simultaneous target analysis of transient-absorption data sets measured with two selective excitations, we resolved the spectral and kinetic properties of the different species present in PSI. WL-PSI can be described as a Bulk Chl a in equilibrium with a higher-energy Chl a, one or two Red Chl a and a reaction-center compartment (WL-RC). Three radical pairs (RPs) have been resolved with very similar properties in the four model organisms. The charge separation is virtually irreversible with a rate of ≈900 ns−1. The second rate, of RP1 → RP2, ranges from 70–90 ns−1 and the third rate, of RP2 → RP3, is ≈30 ns−1. Since RP1 and the Red Chl a are simultaneously present, resolving the RP1 properties is challenging. In Chlamydomonas reinhardtii, the excited WL-RC and Bulk Chl a compartments equilibrate with a lifetime of ≈0.28 ps, whereas the Red and the Bulk Chl a compartments equilibrate with a lifetime of ≈2.65 ps. We present a description of the thermodynamic properties of the model organisms at room temperature.
Original language | English |
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Article number | 4125 |
Pages (from-to) | 1-18 |
Number of pages | 18 |
Journal | International Journal of Molecular Sciences |
Volume | 25 |
Issue number | 7 |
DOIs | |
Publication status | Published - 1 Apr 2024 |
Bibliographical note
This article belongs to the Special Issue New Insights into Photosystem I)---------------------------------------------------------------------------------------
Publisher Copyright:
© 2024 by the authors.
Funding
The PSI complexes of the four model organisms have been excellently isolated and kindly provided by Petra Fromme (Thermosynechococcus elongatus), Wolfgang Lubitz (Chlamydomonas reinhardtii), Jochen Kruip and Matthias R\u00F6gner (SCy6803), and Navasard Karapetyan (Spirulina platensis). For the work carried out at the Max-Planck-Institute in M\u00FClheim a.d. Ruhr, M.G.M. and A.R.H. acknowledge the financial support by the EU Training and Research Networks \u201CHarvest\u201D and \u201CIntro 2\u201D. The Max-Planck-Institute f\u00FCr Chemische Energiekonversion (previously Max-Planck-Institute f\u00FCr Bioanorganische Chemie) is acknowledged for their generous support of this work over many years. This research was funded by the Deutsche Forschungsgemeinschaft for the grant DFG HO-924/3-1 as well as through the Sonderforschungsbereich SFB 663.
Funders | Funder number |
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EU Training and Research Networks “Harvest | |
Deutsche Forschungsgemeinschaft | DFG HO-924/3-1, SFB 663 |
Keywords
- photosynthesis
- target analysis
- transient absorption
- ultrafast spectroscopy