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Biophys J, July 2001, p. 538-546, Vol. 81, No. 1

Fluorescence Lifetime Heterogeneity in Aggregates of LHCII Revealed by Time-Resolved Microscopy

Virginijus Barzda,* Cees J. de Grauw,dagger Jurrien Vroom,dagger Foske J. Kleima,* Rienk van Grondelle,* Herbert van Amerongen,* and Hans C. Gerritsendagger

 *Faculty of Sciences, Department of Physics and Astronomy, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands; and  dagger Debye Institute, Utrecht University, 3508 TA Utrecht, The Netherlands

Two-photon excitation, time-resolved fluorescence microscopy was used to investigate the fluorescence quenching mechanisms in aggregates of light-harvesting chlorophyll a/b pigment protein complexes of photosystem II from green plants (LHCII). Time-gated microscopy images show the presence of large heterogeneity in fluorescence lifetimes not only for different LHCII aggregates, but also within a single aggregate. Thus, the fluorescence decay traces obtained from macroscopic measurements reflect an average over a large distribution of local fluorescence kinetics. This opens the possibility to resolve spatially different structural/functional units in chloroplasts and other heterogeneous photosynthetic systems in vivo, and gives the opportunity to investigate individually the excited states dynamics of each unit. We show that the lifetime distribution is sensitive to the concentration of quenchers contained in the system. Triplets, which are generated at high pulse repetition rates of excitation (>1 MHz), preferentially quench domains with initially shorter fluorescence lifetimes. This proves our previous prediction from singlet-singlet annihilation investigations (Barzda, V., V. Gulbinas, R. Kananavicius, V. Cervinskas, H. van Amerongen, R. van Grondelle, and L. Valkunas. 2001. Biophys. J. 80:2409-2421) that shorter fluorescence lifetimes originate from larger domains in LHCII aggregates. We found that singlet-singlet annihilation has a strong effect in time-resolved fluorescence microscopy of connective systems and has to be taken into consideration. Despite that, clear differences in fluorescence decays can be detected that can also qualitatively be understood.

Biophys J, July 2001, p. 538-546, Vol. 81, No. 1
© 2001 by the Biophysical Society   0006-3495/01/07/538/09  $2.00


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A. Esposito, H. C. Gerritsen, and F. S. Wouters
Fluorescence Lifetime Heterogeneity Resolution in the Frequency Domain by Lifetime Moments Analysis
Biophys. J., December 1, 2005; 89(6): 4286 - 4299.
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