Excitonic Energy Level Structure and Pigment−Protein Interactions in the Recombinant Water-Soluble Chlorophyll Protein. I. Difference Fluorescence Line-Narrowing
| Autor: | Arvi Freiberg, Margus Rätsep, I. Trostmann, Jörg Pieper, Gernot Renger, Harald Paulsen |
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| Rok vydání: | 2011 |
| Předmět: |
Chlorophyll
Chlorophyll b Chlorophyll a Chemistry Phonon Chlorophyll A Exciton Light-Harvesting Protein Complexes Analytical chemistry Water Electrons Brassica Fluorescence Recombinant Proteins Surfaces Coatings and Films chemistry.chemical_compound Spectrometry Fluorescence Materials Chemistry Thermodynamics Physical and Theoretical Chemistry Spectroscopy Excitation |
| Zdroj: | The Journal of Physical Chemistry B. 115:4042-4052 |
| ISSN: | 1520-5207 1520-6106 |
| Popis: | Difference fluorescence line-narrowing spectroscopy at 4.5 K was employed to investigate electron-phonon and electron-vibrational coupling strengths of the lower exciton level of water-soluble chlorophyll-binding protein (WSCP) from cauliflower reconstituted with chlorophyll a or chlorophyll b, respectively. The electron-phonon coupling is found to be moderate with integral Huang-Rhys factors S in the order of 0.81-0.85. A weak dependence of S on excitation wavelength within the inhomogeneously broadened fluorescence origin band is attributed to a sizable contribution of nonresonant excitation that varies with excitation wavelength. The strongly asymmetric and highly structured one-phonon profile is characterized by a peak phonon frequency (ω(m)) of ~24 cm(-1) and further discernible peaks at 48 and 88 cm(-1), respectively. A structural assignment of this unusual one-phonon profile is proposed. As will be shown in the accompanying paper (part II) (DOI 10.1021/jp111457t), the parameters of electron-phonon coupling readily account for shape and position of the fluorescence origin bands at 666.1 and 683.8 nm for chlorophyll b- and chlorophyll a-WSCP, respectively. A rich structure of S(1)→S(0) vibrational frequencies was resolved in the wavenumber range between 180 and 1665 cm(-1) for both chlorophyll a- and chlorophyll b-WSCP. The corresponding individual Huang-Rhys factors fall in the range between 0.0011 and 0.0500. To the best of our knowledge, this is the first report of S-factors for vibrational modes of chlorophyll b. Most remarkable is the presence of two additional modes at 228 and 327 cm(-1) compared with the vibrational spectrum of chlorophyll in solution. The additional modes can most likely be attributed to H-bond formation in the vicinity of the chlorophyll molecule bound by WSCP. |
| Databáze: | OpenAIRE |
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