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Femtosecond visible transient absorption spectroscopy of Chlorophyll f-containing Photosystem I

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Title: Femtosecond visible transient absorption spectroscopy of Chlorophyll f-containing Photosystem I
Authors: Kaucikas, M
Nurnberg, D
Dorhliac, G
Rutherford, A
Van Thor, J
Item Type: Journal Article
Abstract: Photosystem I (PSI) from Chroococcidiopsis thermalis PCC 7203 grown under far-red light (FRL; >725 nm) contains both chlorophyll a and a small proportion of chlorophyll f. Here, we investigated excitation energy transfer and charge separation using this FRL-grown form of PSI (FRL-PSI). We compared femtosecond transient visible absorption changes of normal, white-light (WL)-grown PSI (WL-PSI) with those of FRL-PSI using excitation at 670 nm, 700 nm, and (in the case of FRL-PSI) 740 nm. The possibility that chlorophyll f participates in energy transfer or charge separation is discussed on the basis of spectral assignments. With selective pumping of chlorophyll f at 740 nm, we observe a final ∼150 ps decay assigned to trapping by charge separation, and the amplitude of the resulting P700+•A1−• charge-separated state indicates that the yield is directly comparable to that of WL-PSI. The kinetics shows a rapid 2 ps time constant for almost complete transfer to chlorophyll f if chlorophyll a is pumped with a wavelength of 670 nm or 700 nm. Although the physical role of chlorophyll f is best supported as a low-energy radiative trap, the physical location should be close to or potentially within the charge-separating pigments to allow efficient transfer for charge separation on the 150 ps timescale. Target models can be developed that include a branching in the formation of the charge separation for either WL-PSI or FRL-PSI.
Issue Date: 24-Jan-2017
Date of Acceptance: 1-Dec-2016
URI: http://hdl.handle.net/10044/1/43494
DOI: https://dx.doi.org/10.1016/j.bpj.2016.12.022
ISSN: 1542-0086
Publisher: Biophysical Society
Start Page: 234
End Page: 249
Journal / Book Title: Biophysical Journal
Volume: 112
Issue: 2
Copyright Statement: © 2017 Biophysical Society. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
Sponsor/Funder: The Royal Society
Biotechnology and Biological Sciences Research Cou
The Leverhulme Trust
Funder's Grant Number: WM110001
ERI031013 - BB/L0115061/1
RPG-2014-126
Keywords: Science & Technology
Life Sciences & Biomedicine
Biophysics
RED ANTENNA STATES
ELECTRON-TRANSFER
ENERGY-TRANSFER
CHLAMYDOMONAS-REINHARDTII
REACTION CENTERS
SYNECHOCOCCUS-ELONGATUS
EXCITATION DYNAMICS
CHARGE SEPARATION
PCC 6803
CORE ANTENNA
02 Physical Sciences
03 Chemical Sciences
06 Biological Sciences
Publication Status: Published
Appears in Collections:Faculty of Natural Sciences