Login / Signup

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

Ivo H M van StokkumMarc G MüllerAlfred R Holzwarth
Published in: International journal of molecular sciences (2024)
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.
Keyphrases
  • energy transfer
  • room temperature
  • quantum dots
  • dengue virus
  • optical coherence tomography
  • electronic health record
  • machine learning
  • magnetic resonance
  • zika virus
  • cerebral ischemia