Insight into the alteration of light harvesting antenae in thylakoids by the fluctuating antenna model

Tomas Babelisa, Gediminas Trinkunasb
aDepartment of Theoretical Physics, Faculty of Physics, Vilnius University, Sauletekio Avenue 9, LT-10222 Vilnius, Lithuania; bDepartment of Molecular Compound Physics, Institute of Physics, Center for Physical Sciences and Technology, Savanoriu  ave 231, LT-02300 Vilnius, Lithuania

The fluctuating antenna model has been proposed to describe the nonexponential excitation decay in photosystem II (PS II) [1]. It is based on the coarse grained view of excitation dynamics in antenna [2] combining the fast excitation equilibration inside of light harvesting complexes followed by the slow excitation migration among them and an irreversible charge separation in the reaction center (RC). This model deals with the excitation energy trapping with only two parameters which provide information about the system size and the coordination of light harvesting complexes. Here we report that non-exponential fluorescence decay kinetics of PS I and LHCII aggregates can also be described by the fluctuating antenna model.

With the models of PS I , PS II and LHCII aggregates at hand, we were able to analyze the dynamics of thylakoids under different acclimation conditions and to address the questions that are still open about the spread of photosystems and aggregates during adaptation. By revisiting the fluorescence decays of thylakoids under statte transitions [3] we provide arguments that in the second state a few external antenna complexes of PS II migrate to PS I as well as form the aggregates. Particularly, the analysis of the fluorescence decay data of thylakoid mutants lacking the minor light harvesting complexes of PS II [4] confirmed that these complexes are responsible for regulation of the external antenna size.

References

[1] J. Chmeliov et al. JACS 2014, 25, 8963–72.
[2] K. Broess et al. Biophys. J. 2006, 91, 3776 – 3786.
[3] C. Ünlü et al. PNAS 2014, 111, 3460–3465.
[4] S. Dall’Osto et al. BBA 2014, 1837, 1981–1988.