Abstract
Broadband two-dimensional electronic spectroscopy is applied to investigate the photophysics of the photoactive orange carotenoid protein, which is involved in nonphotochemical quenching in cyanobacteria. Differences in dynamics between the light and dark forms arise from the different structure of the carotenoid in the protein pocket, with consequences for the biological role of the two forms.
Highlights
Photosynthesis powers most life on earth by capturing solar energy and transferring the subsequent excitation to a location for conversion to chemical energy
Broadband two-dimensional electronic spectroscopy is applied to investigate the photophysics of the photoactive orange carotenoid protein, which is involved in nonphotochemical quenching in cyanobacteria
2D relaxation spectra are shown for selected waiting times for OCP from its inactive orange form (OCPo) (Fig. 1(a)) and OCPr (Fig. 1(b))
Summary
Photosynthesis powers most life on earth by capturing solar energy and transferring the subsequent excitation to a location for conversion to chemical energy. The mechanisms of thermal energy dissipation remain elusive [1]; quenching has been shown to involve a photoactivated protein, the orange carotenoid protein (OCP) [2]. We use two-dimensional electronic spectroscopy to probe the absorption and relaxation pathways by excitation of the S0 S2 transition of the carotenoid. These experiments investigate: 1) the photophysics of a carotenoid in a protein environment on ultrafast timescales (OCP is an ideal model system due to its single carotenoid); 2) the differences in excited state dynamics between the dark (orange) and light (red) form to gain insight into the interaction between the carotenoid and the surrounding protein pocket, with consequences for the photo-induced dissipation mechanism
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