Distortion-induced tuning of chlorophyll a electronic properties in LHC proteins

Abstract

In eukaryotic light-harvesting complexes, the protein host tunes chlorophyll- a (Chl a ) site energies through a number of mechanisms (e.g. hydrogen bonding; excitonic/charge-transfer (CT) mixing). However, whether protein-imposed macrocycle distortions also contribute to fine-tuning this energy remains unclear. We have investigated three Chl a -only algal antennas - VCP (from Nannochloropsis oceanica ), rVCP ( Trachydiscus minutus ), and CLH ( Chromera velia ). These complexes show distinct red-shifted absorption features, which at 77 K range from 670 nm up to an extremely red-shifted band at 700 nm (rVCP). By analysis of marker bands in excitation-selective resonance Raman spectra, we have determined the contribution of (i) hydrogen bonding to the keto group (1630–1700 cm −1 region), and/or (ii) macrocycle distortion (bands near 1555 and 1612 cm −1 ) to these red-shifts. Finally, the absence of vibrational features in fluorescence line-narrowing measurements for the reddest rVCP band is consistent with strong excitonic coupling, which we suggest is at the origin of this large red shift. Our results indicate that tuning of the functional properties of Chl a antennas may occur via distortion of the macrocycle.

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BibTeX

@article{bercy2026distortioninduced,
  title = {{Distortion-induced tuning of chlorophyll a electronic properties in LHC proteins}},
  author = {Roxanne Bercy and Juan Romero and Radek Litvin and David Bina and Daniel Finkelstein-Shapiro and Cristian Ilioaia and Andrew Pascal and Bruno Robert and Manuel J. Llansola-Portoles},
  journal = {Biochimica biophysica acta (BBA) - Bioenergetics},
  year = {2026},
  month = oct,
  doi = {10.1016/j.bbabio.2026.149614},
  url = {https://hal.science/hal-05784879v1},
  note = {CC BY},
}

RIS

TY  - JOUR
TI  - Distortion-induced tuning of chlorophyll a electronic properties in LHC proteins
AU  - Roxanne Bercy
AU  - Juan Romero
AU  - Radek Litvin
AU  - David Bina
AU  - Daniel Finkelstein-Shapiro
AU  - Cristian Ilioaia
AU  - Andrew Pascal
AU  - Bruno Robert
AU  - Manuel J. Llansola-Portoles
PY  - 2026
DA  - 2026/10/07
JO  - Biochimica biophysica acta (BBA) - Bioenergetics
DO  - 10.1016/j.bbabio.2026.149614
UR  - https://hal.science/hal-05784879v1
AB  - In eukaryotic light-harvesting complexes, the protein host tunes chlorophyll- a (Chl a ) site energies through a number of mechanisms (e.g. hydrogen bonding; excitonic/charge-transfer (CT) mixing). However, whether protein-imposed macrocycle distortions also contribute to fine-tuning this energy remains unclear. We have investigated three Chl a -only algal antennas - VCP (from Nannochloropsis oceanica ), rVCP ( Trachydiscus minutus ), and CLH ( Chromera velia ). These complexes show distinct red-shifted absorption features, which at 77 K range from 670 nm up to an extremely red-shifted band at 700 nm (rVCP). By analysis of marker bands in excitation-selective resonance Raman spectra, we have determined the contribution of (i) hydrogen bonding to the keto group (1630–1700 cm −1 region), and/or (ii) macrocycle distortion (bands near 1555 and 1612 cm −1 ) to these red-shifts. Finally, the absence of vibrational features in fluorescence line-narrowing measurements for the reddest rVCP band is consistent with strong excitonic coupling, which we suggest is at the origin of this large red shift. Our results indicate that tuning of the functional properties of Chl a antennas may occur via distortion of the macrocycle.
SN  - 0005-2728
SN  - 1879-2650
ER  -

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