Characterization of low-energy chlorophylls in the PSI-LHCI supercomplex from Chlamydomonas reinhardtii. A site-selective fluorescence study.
Almost all photosystem I (PSI) complexes from oxygenic photosynthetic organisms contain chlorophylls that absorb at longer wavelength than that of the primary electron donor P700. We demonstrate here that the low-energy pool of chlorophylls in the PSI-LHCI complex from the green alga Chlamydomonas reinhardtii, containing five to six pigments, is significantly blue-shifted (A(max) at 700 nm at 4 K) compared to that in the PSI core preparations from several species of cyanobacteria and in PSI-LHCI particles from higher plants. This makes them almost isoenergetic with the primary donor. However, they keep the other characteristic features of "red" chlorophylls: clear spectral separation from the bulk chlorophylls, big Stokes shift revealing pronounced electron-phonon coupling, and large homogeneous and inhomogeneous broadening of approximately 170 and approximately 310 cm(-1), respectively.
Gibasiewicz
Krzysztof
K
Department of Physics and Astronomy, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands. krzyszgi@amu.edu.pl
Szrajner
Anna
A
Ihalainen
Janne A
JA
Germano
Marta
M
Dekker
Jan P
JP
van Grondelle
Rienk
R
D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry*; D004583:Electrons; D005453:Fluorescence; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D045331:Photosystem I Protein Complex / Q000737:chemistry*; D014732:Vibration
D045342:Light-Harvesting Protein Complexes; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C001785:chlorophyll P 700