Details

Autor(en) / Beteiligte

• Akhtar, Parveen
• Lambrev, Petar H.

Titel

On the spectral properties and excitation dynamics of long-wavelength chlorophylls in higher-plant photosystem I

Ist Teil von

• Biochimica et biophysica acta. Bioenergetics, 2020-11, Vol.1861 (11), p.148274-148274, Article 148274

Ort / Verlag

Netherlands: Elsevier B.V

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals Complete

Beschreibungen/Notizen

• In higher-plant Photosystem I (PSI), the majority of “red” chlorophylls (absorbing at longer wavelengths than the reaction centre P700) are located in the peripheral antenna, but contradicting reports are given about red forms in the core complex. Here we attempt to clarify the spectroscopic characteristics and quantify the red forms in the PSI core complex, which have profound implication on understanding the energy transfer and charge separation dynamics. To this end we compare the steady-state absorption and fluorescence spectra and picosecond time-resolved fluorescence kinetics of isolated PSI core complex and PSI–LHCI supercomplex from Pisum sativum recorded at 77 K. Gaussian decomposition of the absorption spectra revealed a broad band at 705 nm in the core complex with an oscillator strength of three chlorophylls. Additional absorption at 703 nm and 711 nm in PSI–LHCI indicated up to five red chlorophylls in the peripheral antenna. Analysis of fluorescence emission spectra resolved states emitting at 705, 715 and 722 nm in the core and additional states around 705–710 nm and 733 nm in PSI–LHCI. The red states compete with P700 in trapping excitations in the bulk antenna, which occurs on a timescale of ~20 ps. The three red forms in the core have distinct decay kinetics, probably in part determined by the rate of quenching by the oxidized P700. These results affirm that the red chlorophylls in the core complex must not be neglected when interpreting kinetic experimental results of PSI. [Display omitted] •The plant Photosystem I core antenna contains three red chlorophylls•The core red antenna chlorophylls emit at wavelengths 705, 715, 722 nm•The different red forms have different decay lifetimes•The red forms are not connected by energy transfer at temperature of 77 K