Molecular Origin of Photoprotection in Cyanobacteria Probed by Watermarked Femtosecond Stimulated Raman Spectroscopy.

ABSTRACT: Photoprotection is fundamental in photosynthesis to avoid oxidative photodamage upon excess light exposure. Excited chlorophylls (Chl) are quenched by carotenoids, but the precise molecular origin remains controversial. The cyanobacterial HliC protein belongs to the Hlip family ancestral to plant light-harvesting complexes, and binds Chl a and β-carotene in 2:1 ratio. We analyzed HliC by watermarked femtosecond stimulated Raman spectroscopy to follow the time evolution of its vibrational modes. We observed a 2 ps rise of the C═C stretch band of the 2A_g^- (S₁) state of β-carotene upon Chl a excitation, demonstrating energy transfer quenching and fast excess-energy dissipation. We detected two distinct β-carotene conformers by the C═C stretch frequency of the

SUBMITTER: Hontani Y 

PROVIDER: S-EPMC5942868 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature