PHOTOSYNTHETICA

Photosynthetica 2009, 47(2):232-240 | DOI: 10.1007/s11099-009-0037-0

Fluorescence hole-burning and site-selective studies of LHCII

K. Gibasiewicz^1,*, M. Rutkowski¹, R. van Grondelle²

¹ Department of Physics, Adam Mickiewicz University, Poznań, Poland

² Department of Physics and Astronomy, Vrije Universiteit, Amsterdam, The Netherlands

We report the observation of two types of changes in fluorescence spectra of LHCII at 4.2 K following intense illumination of the sample with a spectrally narrow laser beam at wavelengths between 678 and 686 nm. Nonspecific changes (burning-wavelength independent) are characterized by two relatively broad bands: a positive one at ∼ 678.7 nm and a negative one at ∼ 680.8 nm. These changes reveal a ∼1.3-nm blue shift of the distribution of final emitters in LHCII, from 680.3 nm to ∼ 679.0 nm independent of the excitation wavelength. Specific fluorescence changes (burning-wavelength dependent) are characterized by a sharp hole exactly at the burning wavelength, and positive changes directly to the shorter-and longer-wavelength side of the narrow hole. The negative changes are interpreted as zero-phonon holes, while the positive features are assigned to non-photochemical products. In the low-burning intensity experiment, in addition to the zero-phonon holes, we observed also the holes to the longer wavelength of the zero-phonon hole, which were assigned to a sum of phonon and pseudo-phonon side bands. The shapes of these extra holes are identical to the shapes of the holes revealed in the fluorescence line narrowing experiment. On the basis of the low-burning intensity experiment we estimated the upper limit of the electron-phonon coupling strength for LHCII, characterized by a Huang-Rhys factor of 1.5.

Additional key words: chlorophyll; fluorescence; light-harvesting complex II; line-narrowing; zero-phonon line

Received: December 18, 2008; Accepted: June 9, 2009; Published: June 1, 2009  Show citation