| Author |
Tichý, Josef Vácha, Frantisek Bína, David Polívka, Tomás Fuciman, Marcel Slouf, Václav Kesan, Gürkan Durchan, Milan Staleva, Hristina Litvín, Radek |
| Description |
Author Affiliation: Durchan M ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic); Kesan G ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic.); Slouf V ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic.); Fuciman M ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic.); Staleva H ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic.); Tichý J ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic); Litvín R ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic); Bína D ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic); Vácha F ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic); Polívka T ( Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, Ceské Budejovice, Czech Republic) |
| Abstract |
We report on energy transfer pathways in the main light-harvesting complex of photosynthetic relative of apicomplexan parasites, Chromera velia . This complex, denoted CLH, belongs to the family of FCP proteins and contains chlorophyll (Chl) a , violaxanthin, and the so far unidentified carbonyl carotenoid related to isofucoxanthin. The overall carotenoid-to-Chl- a energy transfer exhibits efficiency over 90% which is the largest among the FCP-like proteins studied so far. Three spectroscopically different isofucoxanthin-like molecules were identified in CLH, each having slightly different energy transfer efficiency that increases from isofucoxanthin-like molecules absorbing in the blue part of the spectrum to those absorbing in the reddest part of spectrum. Part of the energy transfer from carotenoids proceeds via the ultrafast S $_{2}$ channel of both the violaxanthin and isofucoxanthin-like carotenoid, but major energy transfer pathway proceeds via the S $_{1}$ /ICT state of the isofucoxanthin-like carotenoid. Two S $_{1}$ /ICT-mediated channels characterized by time constants of ~ 0.5 and ~ 4 ps were found. For the isofucoxanthin-like carotenoid excited at 480 nm the slower channel dominates, while those excited at 540 nm employs predominantly the fast 0.5 ps channel. Comparing these data with the excited-state properties of the isofucoxanthin-like carotenoid in solution we conclude that, contrary to other members of the FCP family employing carbonyl carotenoids, CLH complex suppresses the charge transfer character of the S $_{1}$ /ICT state of the isofucoxanthin-like carotenoid to achieve the high carotenoid-to-Chl- a energy transfer efficiency. |
