Kinetic modeling of charge-transfer quenching in the CP29 minor complex.
We performed transient absorption (TA) measurements on CP29 minor light-harvesting complexes that were reconstituted in vitro with either violaxanthin (Vio) or zeaxanthin (Zea) and demonstrate that the Zea-bound CP29 complexes exhibit charge-transfer (CT) quenching that has been correlated with the energy-dependent quenching (qE) in higher plants. Simulations of the difference TA kinetics reveal two-phase kinetics for intracomplex energy transfer to the CT quenching site in CP29 complexes, with a fast <500 fs component and a approximately 6 ps component. Specific chlorophyll sites within CP29 are identified as likely locations for CT quenching. We also construct a kinetic model for CT quenching during qE in an intact system that incorporates CP29 as a CT trap and show that the model is consistent with previous in vivo measurements on spinach thylakoid membranes. Finally, we compare simulations of CT quenching in thylakoids with those of the individual CP29 complexes and propose that CP29 rather than LHCII is a site of CT quenching.
Cheng
Yuan-Chung
YC
Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Ahn
Tae Kyu
TK
Avenson
Thomas J
TJ
Zigmantas
Donatas
D
Niyogi
Krishna K
KK
Ballottari
Matteo
M
Bassi
Roberto
R
Fleming
Graham R
GR
D000327:Adsorption; D004579:Electron Transport; D004735:Energy Transfer; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D013055:Spectrophotometry, Infrared; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins
C069660:CP29 light harvesting complex; D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D065146:Zeaxanthins; C005613:violaxanthin