Femtosecond Dynamics of Excited States of Chlorophyll Tetramer in Water-Soluble Chlorophyll-Binding Protein BoWSCP

• Published in: Biochemistry (Moscow) 2023-10, Vol.88 (10), p.1580-1595
• Main Authors: Cherepanov, Dmitry A., Neverov, Konstantin V., Obukhov, Yuriy N., Maleeva, Yulia V., Gostev, Feodor E., Shelaev, Ivan V., Aybush, Arseny V., Kritsky, Michail S., Nadtochenko, Victor A.
• Format: Article
• Language: English
• Subjects: Absorption; Absorption spectra; Analysis; Binding proteins; Biochemistry; Biomedical and Life Sciences; Biomedicine; Bioorganic Chemistry; Broadband; Carrier Proteins; Chlorophyll; Chlorophyll - metabolism; Chlorophyll A; Excitation; Excitation spectra; Excitons; Life Sciences; Microbiology; Oligomers; Photochemical reactions; Photochemicals; Proteins; Spectroscopy; Spectrum Analysis; Tryptophan; Water - chemistry
• ISSN: 0006-2979; 1608-3040
• DOI: 10.1134/S0006297923100139

The paper reports on the absorption dynamics of chlorophyll  a in a symmetric tetrameric complex of the water-soluble chlorophyll-binding protein BoWSCP. It was measured by a broadband femtosecond laser pump-probe spectroscopy within the range from 400 to 750 nm and with a time resolution of 20 fs-200 ps. When BoWSCP was excited in the region of the Soret band at a wavelength of 430 nm, nonradiative intramolecular conversion S 3 →S 1 was observed with a characteristic time of 83 ± 9 fs. When the complex was excited in the region of the Q y band at 670 nm, relaxation transition between two excitonic states of the chlorophyll dimer was observed in the range of 105 ± 10 fs. Absorption spectra of the excited singlet states S 1 and S 3 of chlorophyll  a were obtained. The delocalization of the excited state between exciton-coupled Chl molecules in BoWSCP tetramer changed in time and depended on the excitation energy. When BoWSCP is excited in the Soret band region, an ultrafast photochemical reaction is observed. This could result from the reduction of tryptophan in the vicinity of chlorophyll.