Abstract
Phycobilisomes (PBSs) are the largest light-harvesting antenna in red algae, and feature high efficiency and rate of energy transfer even in a dim environment. To understand the influence of light on the energy transfer in PBSs, two red algae Griffithsia pacifica and Porphyridium purpureum living in different light environment were selected for this research. The energy transfer dynamics in PBSs of the two red algae were studied in time-resolved fluorescence spectroscopy in sub-picosecond resolution. The energy transfer pathways and the related transfer rates were uncovered by deconvolution of the fluorescence decay curve. Four time-components, i.e., 8 ps, 94 ps, 970 ps, and 2288 ps were recognized in the energy transfer in PBSs of G. pacifica, and 10 ps, 74 ps, 817 ps and 1292 ps in P. purpureum. In addition, comparison in energy transfer dynamics between the two red algae revealed that the energy transfer was clearly affected by lighting environment. The findings help us to understand the energy transfer mechanisms of red algae for adaptation to a natural low light environment.
Highlights
Phycobilisomes (PBSs) are the largest light-harvesting antenna in red algae, and feature high efficiency and rate of energy transfer even in a dim environment
The structures of PBS in two red macroalga Griffithsia pacifica (G. pacifica) and Porphyridium purpureum (P. purpureum), who live in different light environments, were illustrated by the cutting-edge cryo-electron microscopy (Cryo-EM) techniques at near-atom level in high resolution, providing a firm structural basis for understanding the mechanisms of energy transfer in PBSs19,20
Different from that in G. pacifica, the fluorescence decay constant of 9 ps in P. purpureum PBSs was due to the energy transfer time between PE and PC, because its amplitude shown in Fig. 3d was positive in the blue side and quickly turned negative with a minimum around 630 nm, which is consistent with that of the P. purpureum PBSs in time-resolved fluorescence spectrum (Fig. 2d)
Summary
Phycobilisomes (PBSs) are the largest light-harvesting antenna in red algae, and feature high efficiency and rate of energy transfer even in a dim environment. Structures of red algae P. purpureum and G. pacifica, which have been clearly understood, were selected to study the energy transfer difference within PBSs. The steady-state and time-resolved fluorescence spectra of both red algae were measured and the sequential energy flow among PBPs in PBSs was shown.
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