Pure Appl. Chem., 2005, Vol. 77, No. 6, pp. 925-945
doi:10.1351/pac200577060925
Carotenoid-chlorophyll complexes: Ready-to-harvest*
Harsha M. Vaswani, Nancy E. Holt, and Graham R. Fleming
Department of Chemistry, University of California, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
Abstract:
The fundamental interactions between naturally occurring pigments in light-harvesting systems are responsible for the high efficiency of the photosynthetic apparatus. We describe the role of carotenoids (Cars) in light-harvesting systems, including our work elucidating the mechanism of energy transfer from the optically dark Car singlet excited state (S1) to chlorophyll (Chl) and calculations on the electronic structure of Cars by means of time-dependent density functional theory (TDDFT). We highlight new studies on the charge-transfer state of the Car, peridinin (Per), which enhances the light-harvesting efficiency of the Car by increasing the electronic coupling to Chl. The role of another Car, zeaxanthin (Zea), is discussed with respect to its role in the mechanism of the feedback deexcitation quenching in green plants, a vital regulation process under light conditions which exceed photosynthetic capacity. Lastly, we provide insight on how the 96 Chls in Photosystem I are optimized to generate a pigment-protein complex which utilizes solar energy with near unit efficiency.
Keywords: carotenoid-chlorophyll complexes; dependent density; feedback deexcitation quenching in green plants; functional theory; light harvesting; mechanism of energy transfer.
*Paper based on the acceptance lecture for the 2004 Porter Medal, presented at the XXth IUPAC Symposium on Photochemistry, Granada, Spain, 17-22 July 2004. Other presentations are published in this issue, pp. 925-1085.
All articles from the XXth IUPAC Symposium on Photochemistry, Granada, Spain, 17–22 July 2004.