Excitonic energy level structure and pigment-protein interactions in the recombinant water-soluble chlorophyll protein. II. Spectral hole-burning experiments
| Autor: | Margus Rätsep, Harald Paulsen, Arvi Freiberg, I. Trostmann, Jörg Pieper, Hans Joachim Eichler, Gernot Renger, Christoph Theiss, Franz-Josef Schmitt |
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| Rok vydání: | 2011 |
| Předmět: |
Chlorophyll
Chlorophyll a Exciton Analytical chemistry Light-Harvesting Protein Complexes Electrons Brassica Vibration Spectral line chemistry.chemical_compound Materials Chemistry Physical and Theoretical Chemistry Physics::Biological Physics Chlorophyll A Water Fluorescence Recombinant Proteins Surfaces Coatings and Films Wavelength Spectrometry Fluorescence chemistry Excited state Spectral hole burning Thermodynamics Atomic physics |
| Zdroj: | The journal of physical chemistry. B. 115(14) |
| ISSN: | 1520-5207 |
| Popis: | Persistent spectral hole burning at 4.5 K has been used to investigate the excitonic energy level structure and the excited state dynamics of the recombinant class-IIa water-soluble chlorophyll-binding protein (WSCP) from cauliflower. The hole-burned spectra are composed of four main features: (i) a narrow zero-phonon hole (ZPH) at the burn wavelength, (ii) a number of vibrational ZPHs, (iii) a broad low-energy hole at ~665 and ~683 nm for chlorophyll b- and chlorophyll a-WSCP, respectively, and (iv) a second satellite hole at ~658 and ~673 nm for chlorophyll b- and chlorophyll a-WSCP, respectively. The doublet of broad satellite holes is assigned to an excitonically coupled chlorophyll dimer. The lower-energy holes at ~665 and ~683 nm for chlorophyll b- and chlorophyll a-WSCP, respectively, represent the lower exciton states. Taking into account the parameters of electron-phonon coupling, the lower exciton state can be assigned as the fluorescence origin. The lower exciton state is populated by two processes: (i) exciton relaxation from the higher exciton state and (ii) vibrational relaxation within the lower exciton state. Assuming identical site energies for the two excitonically coupled chlorophyll molecules, the dipole-dipole interaction energy J is directly determined to be 85 and 100 cm(-1) for chlorophyll b- and chlorophyll a-WSCP, respectively, based on the positions of the satellite holes. The Gaussian low-energy absorption band identified by constant fluence hole burning at 4.5 K has a width of ~150 cm(-1) and peaks at 664.9 and 682.7 nm for chlorophyll b- and chlorophyll a-WSCP, respectively. The action spectrum is broader and blue-shifted compared to the fluorescent lower exciton state. This finding can be explained by a slow protein relaxation between energetically inequivalent conformational substates within the lowest exciton state in agreement with the results of Schmitt et al. (J. Phys. Chem. B2008, 112, 13951). |
| Databáze: | OpenAIRE |
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