Energy Transfer and Radical-Pair Dynamics in Photosystem I with Different Red Chlorophyll a Pigments

Ivo H.M. van Stokkum*, Marc G. Müller, Alfred R. Holzwarth

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

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 languageEnglish
Article number4125
Pages (from-to)1-18
Number of pages18
JournalInternational Journal of Molecular Sciences
Volume25
Issue number7
DOIs
Publication statusPublished - 1 Apr 2024

Bibliographical note

This article belongs to the Special Issue New Insights into Photosystem I)

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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.

FundersFunder number
EU Training and Research Networks “Harvest
Deutsche ForschungsgemeinschaftDFG HO-924/3-1, SFB 663

    Keywords

    • photosynthesis
    • target analysis
    • transient absorption
    • ultrafast spectroscopy

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