Red chlorophyll excitation dynamics in Arthrospira platensis photosystem I trimeric complexes as studied by femtosecond transient absorption spectroscopy

Abstract

Edited by Richard Cogdell Keywords:Photosystem I trimer Long-wavelength red chlorophyll form Femtosecond pump-probe spectroscopy Arthrospira platensis a b s t r a c t Femtosecond absorption spectroscopy was applied to study for the first time excitation dynamics in isolated photosystem I trimers from Arthrospira platensis, which display extremely long-wavelength absorption peaks. Pump-probe spectra observed at 77 K in the timescale of dozens of picoseconds upon 70-fs excitation revealed two maxima near 710 and 730 nm, which correspond to red chlorophyll forms. Bleaching at 680 nm developed in $200 fs, whereas the bleaching kinetics at 710 and 730 nm exhibited two components with time constants of 1 and 5.5 ps. Comparison of the kinetics of bleaching development at 710 nm and 730 nm with that of bleaching decay at 680 nm indicated that both long-wavelength forms of trimers are populated mainly via direct energy transfer from bulk chlorophyll.

Femtosecond Visible Transient Absorption Spectroscopy of Chlorophyll f -Containing Photosystem I

“…Recently, Kompanets et al. ( 29 ) performed TA measurements of Arthrospira platensis PSI, which contains extremely red-shifted Chls. They observed two bleaches developing at 710 nm and 730 nm with 1 ps and 5.5 ps time constants, respectively.…”

Single Molecule Fluorescence Spectroscopy of PSI Trimers from Arthrospira platensis: A Computational Approach

“…Surprisingly, the fluorescence intensity of the LWCs of PSI trimer from Arthrospira platensis depends on the redox state of P700. The F760 peak is much weaker than F740 when the P700 of the RC is oxidized [22,23].…”