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Donatas Zigmantas. Portrait.

Donatas Zigmantas

Professor

Donatas Zigmantas. Portrait.

Light harvesting in purple bacteria does not rely on resonance fine-tuning in peripheral antenna complexes

Author

  • Erika Keil
  • Heiko Lokstein
  • Richard Cogdell
  • Jürgen Hauer
  • Donatas Zigmantas
  • Erling Thyrhaug

Summary, in English

The ring-like peripheral light-harvesting complex 2 (LH2) expressed by many phototrophic purple bacteria is a popular model system in biological light-harvesting research due to its robustness, small size, and known crystal structure. Furthermore, the availability of structural variants with distinct electronic structures and optical properties has made this group of light harvesters an attractive testing ground for studies of structure–function relationships in biological systems. LH2 is one of several pigment-protein complexes for which a link between functionality and effects such as excitonic coherence and vibronic coupling has been proposed. While a direct connection has not yet been demonstrated, many such interactions are highly sensitive to resonance conditions, and a dependence of intra-complex dynamics on detailed electronic structure might be expected. To gauge the sensitivity of energy-level structure and relaxation dynamics to naturally occurring structural changes, we compare the photo-induced dynamics in two structurally distinct LH2 variants. Using polarization-controlled 2D electronic spectroscopy at cryogenic temperatures, we directly access information on dynamic and static disorder in the complexes. The simultaneous optimal spectral and temporal resolution of these experiments further allows us to characterize the ultrafast energy relaxation, including exciton transport within the complexes. Despite the variations in PPC molecular structure manifesting as clear differences in electronic structure and disorder, the energy-transport and—relaxation dynamics remain remarkably similar. This indicates that the light-harvesting functionality of purple bacteria within a single LH2 complex is highly robust to structural perturbations and likely does not rely on finely tuned electronic- or electron-vibrational resonance conditions.

Department/s

  • Chemical Physics
  • LU Profile Area: Light and Materials
  • LTH Profile Area: Photon Science and Technology
  • LTH Profile Area: Nanoscience and Semiconductor Technology
  • NanoLund: Centre for Nanoscience

Publishing year

2024-09

Language

English

Pages

191-201

Publication/Series

Photosynthesis Research

Volume

161

Issue

3

Document type

Journal article

Publisher

Springer

Topic

  • Atom and Molecular Physics and Optics
  • Biophysics

Keywords

  • Energy transfer
  • Excitons
  • Light-harvesting
  • Ultrafast spectroscopy

Status

Published

ISBN/ISSN/Other

  • ISSN: 0166-8595