EXCITATION ENERGY TRANSFER AND PHOTOREGULATORY MECHANISMS IN INTACT PHYCOBILISOMES USING TWO-DIMENSIONAL ELECTRONIC SPECTROSCOPY

Sil, Sourav

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https://hdl.handle.net/2142/122677 Copy

Description

Title

EXCITATION ENERGY TRANSFER AND PHOTOREGULATORY MECHANISMS IN INTACT PHYCOBILISOMES USING TWO-DIMENSIONAL ELECTRONIC SPECTROSCOPY

Author(s)

Sil, Sourav

Contributor(s)

• Beck, Warren F.
• Kerfeld, Cheryl A.
• Rose, Justin B.
• Leslie, Chase H.
• T.M., Nila Mohan
• Tilluck, Ryan W.

Issue Date

2023-06-21

Keyword(s)

Dynamics and kinetics

Abstract

The phycobilisome is the principal light-harvesting chromoprotein complex in cyanobacteria and red algae. We have employed broadband multidimensional electronic spectroscopy with 6.7-fs laser pulses for the first time to study the excitation energy transfer mechanisms in intact phycobilisomes isolated from Fremyella diplosiphon. The results show that excitation energy transfer pathways include delocalized optical excitations of bilin (linear tetrapyrrole) chromophores, which transfer excitation energy along the rods in <600 fs. Excitation energy moves more slowly from the rods to the core on the >10 ps time scale, indicating that excitation energy is localized on individual bilin chromophores in the allophycocyanin-containing segments of the phycobilisome. The intramolecular charge-transfer character of the β84 chromophore in allophycocyanin would strongly favor dynamic exciton localization upon transfer of excitation energy from the rod segments. This phenomenon contributes to a kinetic bottleneck, which allows photoregulatory mechanisms, including that involving binding of the orange carotenoid protein, to operate efficiently in the core. In phycobilisomes isolated from Fremyella diplosiphon grown under red light, in contrast to those grown under white light, the terminal emitting APC680 segments exhibit significantly shorter excited-state lifetimes. These findings further show that trapping bilin sites are accumulated in the core of the phycobilisome during growth as part of a chromatic adaptation response.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122677

DOI

https://doi.org/10.15278/isms.2023.7212

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