TY - JOUR
T1 - Energy coupling in the PSI-LHCI supercomplex from the green alga chlamydomonas reinhardtii
AU - Melkozernov, Alexander N.
AU - Kargul, Joanna
AU - Lin, Su
AU - Barber, James
AU - Blankenship, Robert E.
PY - 2004/7/22
Y1 - 2004/7/22
N2 - Energy transfer and trapping in the PSI-LHCI supercomplex from the green alga Chlamydomonas reinhardtii have been studied using femtosecond transient absorption and picosecond fluorescence spectroscopy at room temperature. Data suggest that excitations of the PSI-LHCI supercomplex at 700 nm have similar probabilities of excitation of either the primary donor in the PSI core (absorbing at 697 nm) or low-energy Chls in the LHCI (red pigments) that presumably absorb at this spectral region. Both transient absorption and picosecond fluorescence spectroscopy indicate a biphasic overall decay of the excitation in the PSI-LHCI. The process includes a photochemical trapping in the PSI core antenna occurring with a typical lifetime of 25 ± 3 ps and a significantly slower excitation decay phase in the PSI-LHCI supercomplex occurring with a lifetime of 104 ± 20 ps and maximum of absorption changes around 685 nm. The slow excitation decay process suggests presence of an energy transfer pathway from the LHCI to the PSI core, which introduces a diffusion-limited step, in contrast to optimized and energetically well coupled excitation dynamics in the PSI core and CP43-PSI supercomplexes from iron-stress-induced cyanobacteria. Although LHCI in green algae seems to be similar to those isolated from higher plants the data demonstrate apparent differences in the excitation dynamics suggesting differences in molecular organizations and causes of the red spectral shift associated with PSI. Data of time-resolved spectroscopy are discussed based on the available structural models of PSI-LHCI supercomplexes.
AB - Energy transfer and trapping in the PSI-LHCI supercomplex from the green alga Chlamydomonas reinhardtii have been studied using femtosecond transient absorption and picosecond fluorescence spectroscopy at room temperature. Data suggest that excitations of the PSI-LHCI supercomplex at 700 nm have similar probabilities of excitation of either the primary donor in the PSI core (absorbing at 697 nm) or low-energy Chls in the LHCI (red pigments) that presumably absorb at this spectral region. Both transient absorption and picosecond fluorescence spectroscopy indicate a biphasic overall decay of the excitation in the PSI-LHCI. The process includes a photochemical trapping in the PSI core antenna occurring with a typical lifetime of 25 ± 3 ps and a significantly slower excitation decay phase in the PSI-LHCI supercomplex occurring with a lifetime of 104 ± 20 ps and maximum of absorption changes around 685 nm. The slow excitation decay process suggests presence of an energy transfer pathway from the LHCI to the PSI core, which introduces a diffusion-limited step, in contrast to optimized and energetically well coupled excitation dynamics in the PSI core and CP43-PSI supercomplexes from iron-stress-induced cyanobacteria. Although LHCI in green algae seems to be similar to those isolated from higher plants the data demonstrate apparent differences in the excitation dynamics suggesting differences in molecular organizations and causes of the red spectral shift associated with PSI. Data of time-resolved spectroscopy are discussed based on the available structural models of PSI-LHCI supercomplexes.
UR - http://www.scopus.com/inward/record.url?scp=3442892370&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=3442892370&partnerID=8YFLogxK
U2 - 10.1021/jp049375n
DO - 10.1021/jp049375n
M3 - Article
AN - SCOPUS:3442892370
VL - 108
SP - 10547
EP - 10555
JO - Journal of Physical Chemistry B
JF - Journal of Physical Chemistry B
SN - 1520-6106
IS - 29
ER -