Light harvesting in oxygenic photosynthesis: Structural biology meets spectroscopy
Architectures for light harvesting Conversion of light energy into chemical energy ultimately drives most biochemistry on earth. Photosynthetic organisms use diverse chemical and biological structures to harvest light in different environmental contexts. Croce and van Amerongen synthesized recent st...
Saved in:
| Published in: | Science (American Association for the Advancement of Science) 2020-08, Vol.369 (6506) |
|---|---|
| Main Authors: | , |
| Format: | Article |
| Language: | eng |
| Subjects: | |
| Online Access: | Get full text |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Architectures for light harvesting Conversion of light energy into chemical energy ultimately drives most biochemistry on earth. Photosynthetic organisms use diverse chemical and biological structures to harvest light in different environmental contexts. Croce and van Amerongen synthesized recent structural and spectroscopic work on photosystem complexes from oxygenic photosynthetic organisms. To best capture light, photosystems contain accessory light-harvesting complexes harboring complex networks of pigments that shuttle electronic excitations toward the core complex, which contains the reaction center. The arrangement of pigments and their connectivity, as seen in high-resolution x-ray and cryo–electron microscopy structures, inform our understanding of energy transfer rates derived from spectroscopic measurements and vice versa. The model that emerges is one of many parallel and unconnected pathways for energy transfer into the reaction center from the exterior light-harvesting complexes. Science , this issue p. eaay2058
BACKGROUND The harvesting of photons is the first step in photosynthesis, the biological process that transforms solar energy into chemical energy. The photosynthetic membranes of algae and plants are packed with protein complexes binding many chlorophyll and carotenoid pigments, which are combined to form functional units. These units, called the photosystem I and II (PSI and PSII) supercomplexes, are composed of a reaction center (RC) where photochemistry occurs and an antenna comprising hundreds of pigments. Because even direct sunlight is a dilute form of energy, the antenna is crucial to increasing the light-harvesting capacity of the RC. After light is absorbed by a pigment in one of these complexes, excitation energy transfer (EET) to a nearby pigment occurs. EET proceeds until the excitation reaches the RC, where charge separation (CS) takes place. The faster the energy reaches the RC, the higher the photon-to-electron conversion efficiency is because this process needs to beat the natural excited-state decay of the pigments. The trapping in the RCs of PSI and PSII in vivo occurs within 20 to 300 ps, and the maximal quantum efficiency is close to 1.0 for PSI and 0.9 for PSII. How is this high efficiency achieved? ADVANCES In recent years, structures of supercomplexes from various algae and plants have been determined at near-atomic resolution using cryo–electron microscopy. These structures revealed the pigment-binding archite |
|---|---|
| ISSN: | 0036-8075 1095-9203 |