Chlorophyll Orientation and Exciton Migration in the Photosynthetic Membrane

J. Breton, N. E. Geacintov

Research output: Chapter in Book/Report/Conference proceedingChapter


Measurements of the linear dichroism and of the polarization of the fluorescence with oriented chloroplasts have revealed a definite orientation of the pigment molecules with respect to the membrane plane. The Qy transition moments of the chlorophyll a molecules are more closely inclined with respect to this plane for the forms absorbing at longer wavelengths than for those absorbing at shorter wavelengths. The fluorescence depolarization by energy transfer, determined with magnetically-oriented chloroplasts, indicates that the degree of local order increases with wavelength for the different (absorption wavelength) forms of chlorophyll a in viva Laser pulses of either picosecond or microsecond duration have been used to probe the emission spectrum, lifetime and quantum yield of fluorescence of chloroplasts at various temperatures. With single picosecond pulses, singletsinglet annihilations occur within the light-harvesting chlorophyll molecules. In the case of microsecond pulses, triplet excitons act as efficient quenchers of the singlets. By monitoring both the yield of carotenoid triplets and of the fluorescence during and after a laser flash, one can show that the carotenoid triplets account for part of but not all the fluorescence quenching.

Original languageEnglish (US)
Title of host publicationChlorophyll Organization and Energy Transfer in Photosynthesis
Number of pages20
ISBN (Electronic)9780470720431
ISBN (Print)0444900446, 9780444900449
StatePublished - May 30 2008


  • Bipartite model
  • Excitation energy
  • Fluorescence bands
  • Photochemical apparatus
  • Photosynthesis

ASJC Scopus subject areas

  • General Agricultural and Biological Sciences


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