TY - JOUR
T1 - Picosecond fluorescence of intact and dissolved PSI-LHCI crystals
AU - Van Oort, Bart
AU - Amunts, Alexey
AU - Borst, Jan Willem
AU - Van Hoek, Arie
AU - Nelson, Nathan
AU - Van Amerongen, Herbert
AU - Croce, Roberta
N1 - Funding Information:
This work is part of the research program of the Stichting voor Fundamenteel onderzoek der Materie (FOM), which is financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO). B.v.O. was supported by FOM. N.N. acknowledges support from the Israel Science Foundation (grant 356/06). R. C. acknowledges support from “NWO, Earth and Life Science (ALW)”, through a VIDI grant.
PY - 2008/12/15
Y1 - 2008/12/15
N2 - Over the past several years, many crystal structures of photosynthetic pigment-protein complexes have been determined, and these have been used extensively to model spectroscopic results obtained on the same proteins in solution. However, the crystal structure is not necessarily identical to the structure of the protein in solution. Here, we studied picosecond fluorescence of photosystem I light-harvesting complex I (PSI-LHCI), a multisubunit pigment-protein complex that catalyzes the first steps of photosynthesis. The ultrafast fluorescence of PSI-LHCI crystals is identical to that of dissolved crystals, but differs considerably from most kinetics presented in the literature. In contrast to most studies, the data presented here can be modeled quantitatively with only two compartments: PSI core and LHCI. This yields the rate of charge separation from an equilibrated core (22.5 ± 2.5 ps) and rates of excitation energy transfer from LHCI to core (kLC) and vice versa (kCL). The ratio between these rates, R = kCL/k LC, appears to be wavelength-dependent and scales with the ratio of the absorption spectra of LHCI and core, indicating the validity of a detailed balance relation between both compartments. kLC depends slightly but nonsystematically on detection wavelength, averaging (9.4 ± 4.9 ps) -1. R ranges from 0.5 (<690 nm) to ∼;1.3 above 720 nm.
AB - Over the past several years, many crystal structures of photosynthetic pigment-protein complexes have been determined, and these have been used extensively to model spectroscopic results obtained on the same proteins in solution. However, the crystal structure is not necessarily identical to the structure of the protein in solution. Here, we studied picosecond fluorescence of photosystem I light-harvesting complex I (PSI-LHCI), a multisubunit pigment-protein complex that catalyzes the first steps of photosynthesis. The ultrafast fluorescence of PSI-LHCI crystals is identical to that of dissolved crystals, but differs considerably from most kinetics presented in the literature. In contrast to most studies, the data presented here can be modeled quantitatively with only two compartments: PSI core and LHCI. This yields the rate of charge separation from an equilibrated core (22.5 ± 2.5 ps) and rates of excitation energy transfer from LHCI to core (kLC) and vice versa (kCL). The ratio between these rates, R = kCL/k LC, appears to be wavelength-dependent and scales with the ratio of the absorption spectra of LHCI and core, indicating the validity of a detailed balance relation between both compartments. kLC depends slightly but nonsystematically on detection wavelength, averaging (9.4 ± 4.9 ps) -1. R ranges from 0.5 (<690 nm) to ∼;1.3 above 720 nm.
UR - http://www.scopus.com/inward/record.url?scp=58749095136&partnerID=8YFLogxK
U2 - 10.1529/biophysj.108.140467
DO - 10.1529/biophysj.108.140467
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C2 - 18931256
AN - SCOPUS:58749095136
SN - 0006-3495
VL - 95
SP - 5851
EP - 5861
JO - Biophysical Journal
JF - Biophysical Journal
IS - 12
ER -