The Impact of Carotenoid Energy Levels on the Exciton Dynamics and Singlet-Triplet Annihilation in Isolated Bacterial Light-Harvesting 2 Complexes
The result's identifiers
Result code in IS VaVaI
<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F25%3A10507738" target="_blank" >RIV/00216208:11320/25:10507738 - isvavai.cz</a>
Result on the web
<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=t5POBhSaKC" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=t5POBhSaKC</a>
DOI - Digital Object Identifier
<a href="http://dx.doi.org/10.1021/acs.jpcb.5c06284" target="_blank" >10.1021/acs.jpcb.5c06284</a>
Alternative languages
Result language
angličtina
Original language name
The Impact of Carotenoid Energy Levels on the Exciton Dynamics and Singlet-Triplet Annihilation in Isolated Bacterial Light-Harvesting 2 Complexes
Original language description
The light-harvesting 2 (LH2) complex of purple phototrophic bacteria plays a critical role in absorbing solar energy and distributing the excitation energy. Exciton dynamics within LH2 complexes are controlled by the structural arrangement and energy levels of the bacteriochlorophyll (BChl) and carotenoid (Car) pigments. However, there is still debate over the competing light-harvesting versus energy-dissipation pathways. In this work, we compared five variants of the LH2 complex from genetically modified strains of Rhodobacter sphaeroides, all containing the same BChls but different Cars with increasing conjugation: zeta-carotene (N = 7; LH2(Zeta)), neurosporene (N = 9; LH2(Neu)), spheroidene (N = 10; LH2(Spher)), lycopene (N = 11; LH2(Lyco)), and spirilloxanthin (N = 13; LH2(Spir)). Absorption measurements confirmed that the Car excited-state energy decreased with increasing conjugation. Similarly, fluorescence spectra showed that the B850 BChl emission peak had an increasing red shift from LH2(Zeta)->(LH2(Neu)/LH2(Spher))-> LH2(Lyco)-> LH2(Spir). In contrast, time-resolved fluorescence and ultrafast transient absorption (fs-TA) revealed similar excited-state lifetimes (similar to 1 ns) for all complexes except LH2(Spir) (similar to 0.7 ns). From fs-TA analysis, an additional similar to 7 ps nonradiative dissipation step from B850 BChl was observed for LH2(Zeta). Further, singlet-singlet and singlet-triplet annihilation studies showed a similar to 50% average fluorescence lifetime reduction in LH2(Zeta) at high laser power and high repetition rate, compared to similar to 10-15% reductions in LH2(Neu)/LH2(Spher)/LH2(Lyco) and minimal lifetime change in LH2(Spir). In LH2(Zeta), the fastest decay component (<50 ps) became prominent at high repetition rates, consistent with strong singlet-triplet annihilation. Nanosecond TA measurements revealed long-lived (>40 mu s) BChl triplet states in LH2(Zeta) and signs of damage caused by singlet oxygen, whereas other LH2s showed faster triplet quenching (similar to 18 ns) by Cars. These findings highlight a key design principle of LH2 complexes: the Car triplet energy must be significantly lower than the BChl triplet energy to efficiently quench BChl triplets that otherwise act as potent "trap states," causing exciton annihilation in laser-based experiments or photodamage in native membranes.
Czech name
—
Czech description
—
Classification
Type
J<sub>imp</sub> - Article in a specialist periodical, which is included in the Web of Science database
CEP classification
—
OECD FORD branch
10301 - Atomic, molecular and chemical physics (physics of atoms and molecules including collision, interaction with radiation, magnetic resonances, Mössbauer effect)
Result continuities
Project
—
Continuities
I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace
Others
Publication year
2025
Confidentiality
S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů
Data specific for result type
Name of the periodical
Journal of Physical Chemistry B
ISSN
1520-6106
e-ISSN
1520-5207
Volume of the periodical
129
Issue of the periodical within the volume
49
Country of publishing house
US - UNITED STATES
Number of pages
19
Pages from-to
12642-12660
UT code for WoS article
001622900900001
EID of the result in the Scopus database
2-s2.0-105024725767