Anisotropy of photosynthetic membranes and the degree of fluorescence polarization

J. F. Becker, J. Breton, Nicholas Geacintov, F. Trentacosti

Research output: Contribution to journalArticle

Abstract

The degree of fluoresence polarization, P, of unoriented and magnetically oriented spinach chloroplasts as a function of excitation (400-680 nm) and emission wavelengths (675-750 nm) is reported. For unoriented chloroplasts P can be divided into two contributions, PIN and PAN. The latter arises from the optical anisotropy of the membranes which is due to the orientation with respect to the membrane plane of pigment molecules in vivo. The intrinsic polarization PIN, which reflects the energy transfer between different pigment molecules and their degree of mutual orientation, can be measured unambiguously only if (1) oriented membranes are used and the fluorescence is viewed along a direction normal to the membrane planes, and (2) the excitation is confined to the Qy (≈ 660-680 nm) absorption band of chlorophyll in vivo. With 670-680 nm excitation, values of P using unoriented chloroplasts can be as high as +14%, mostly reflecting the orientational anisotropy of the pigments. Using oriented chloroplasts, PIN is shown to be +5±1%. The excitation wavelength dependence studies of PIN indicate that the carotenoid and chlorophyll Qy transition moments tend to be partially oriented with respect to each other on a local level (within a given photosynthetic unit or its immediate neighbors).

Original languageEnglish (US)
Pages (from-to)531-544
Number of pages14
JournalBBA - Bioenergetics
Volume440
Issue number3
DOIs
StatePublished - Sep 13 1976

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Photosynthetic membranes
Fluorescence Polarization
Anisotropy
Chloroplasts
Fluorescence
Pigments
Polarization
Membranes
Chlorophyll
Optical anisotropy
Wavelength
Molecules
Spinacia oleracea
Energy Transfer
Carotenoids
Energy transfer
Absorption spectra

ASJC Scopus subject areas

  • Biophysics
  • Medicine(all)

Cite this

Anisotropy of photosynthetic membranes and the degree of fluorescence polarization. / Becker, J. F.; Breton, J.; Geacintov, Nicholas; Trentacosti, F.

In: BBA - Bioenergetics, Vol. 440, No. 3, 13.09.1976, p. 531-544.

Research output: Contribution to journalArticle

Becker, J. F. ; Breton, J. ; Geacintov, Nicholas ; Trentacosti, F. / Anisotropy of photosynthetic membranes and the degree of fluorescence polarization. In: BBA - Bioenergetics. 1976 ; Vol. 440, No. 3. pp. 531-544.
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