Excitation Wavelength-Dependent Electron-Phonon and Electron-Vibrational Coupling in the CP29 Antenna Complex of Green Plants

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• 作者：Margus R&auml ; tsep ; Jö ; rg Pieper ; Klaus-Dieter Irrgang ; Arvi Freiberg
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：January 10, 2008
• 年：2008
• 卷：112
• 期：1
• 页码：110 - 118
• 全文大小：215K
• 年卷期：v.112,no.1(January 10, 2008)
• ISSN：1520-5207

文摘

Electron-phonon and electron-vibrational coupling strengths of a weakly (excitonically) coupled chlorophylla S₁ S₀ transition of the CP29 antenna complex of plant photosystem II were studied by differencefluorescence-line-narrowing spectroscopy at 4.5 K. A strong, almost linear increase of the electron-phononcoupling strength toward longer wavelengths was observed, with Huang-Rhys factors S_ph increasing from0.41 ± 0.05 at 680 nm to about 0.66 ± 0.07 at 688 nm. The former and latter wavelengths are located closeto the peak and on the red edge of the inhomogeneous site distribution function, respectively. The experimentallyobtained wavelength dependence of S_ph may originate either from an alteration of the electron-phonon couplingstrength by the local environment of the fluorescing chromophore and/or from the presence of two isoformsof CP29, which are characterized by different coupling strengths to the protein environment. The one-phononprofile peaks at _m = 22 cm^-1 and is described by an asymmetric function composed of a Gaussian low-energy wing and a Lorentzian high-energy tail with half-widths at half-maximum of 10 ± 1 and 60 ± 10cm^-1, respectively. Thirty-nine individual vibrational modes between 90 and 1665 cm^-1 were resolved, andtheir Huang-Rhys factors were determined, which fall in the range between 0.0004 and 0.032. The broadfeature present in the overlap region of phonon and vibrational modes at about 90 cm^-1 is characterized byS = 0.048. An integral value of vibrational coupling strengths S_vib = 0.36 ± 0.05 was determined, which issimilar to that observed earlier for the trimeric LHC II complex.