Femtosecond excited-state dynamics in chlorosomal carotenoids of the photosynthetic bacterium Chloroflexus aurantiacus revealed by near infrared pump-probe spectroscopy.
Phys Chem Chem Phys
; 23(22): 12761-12770, 2021 Jun 09.
Article
em En
| MEDLINE
| ID: mdl-34042141
ABSTRACT
In photosynthetic green bacteria, chlorosomes provide light harvesting with high efficiency. Chlorosomal carotenoids (Cars) participate in light harvesting together with the main pigment, bacteriochlorophyll (BChl) c/d/e. In the present work, we studied the excited-state dynamics in Cars from Chloroflexus (Cfx.) aurantiacus chlorosomes by near infrared pump-probe spectroscopy with 25 fs temporal resolution at room temperature. The S2 state of Cars was excited at a wavelength of â¼520 nm, and the absorption changes were probed at 860-1000 nm where the excited state absorption (ESA) of the Cars S2 state occurred. Global analysis of the spectroscopy data revealed an ultrafast (â¼15 fs) and large (>130 nm) red shift of the S2 ESA spectrum together with the well-known S2 â S1 IC (â¼190 fs) and Cars â BChl c EET (â¼120 fs). The S2 lifetime was found to be â¼74 fs. Our findings are in line with earlier results on the excited-state dynamics in Cars in vitro. To explain the extremely fast S2 dynamics, we have tentatively proposed two alternative schemes. The first scheme assumed the formation of a vibrational wavepacket in the S2 state, the motion of which caused a dynamical red shift of the S2 ESA spectrum. The second scheme assumed the presence of two potential minima in the S2 state and incoherent energy transfer between them.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Carotenoides
/
Chloroflexus
Idioma:
En
Revista:
Phys Chem Chem Phys
Ano de publicação:
2021
Tipo de documento:
Article