LUMINESCENCE OF BACTERIORHODOPSIN IN PURPLE MEMBRANES FROM HALOBACTERIUM HALOBIUM CELLS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 21  (2) , 313-320
Abstract
Red luminescence of purple membranes from H. halobium cells was observed and its emission, excitation and polarization spectra were investigated. The light-induced absorption and luminescence changes in 1 sample were measured. The bands in the spectra are attributed to a number of bacteriorhodopsin (BR) forms: .**GRAPHIC**. BR600-620, .**GRAPHIC**. where the superscript is the position of the luminescence maxima, and the subscript is the absorption maxima. Proceeding from the BR quantum yield of the luminescence (10-3) and the photoreaction (10-1), the photoisomerization rate constant of the latter was estimated (1011 sec-1). The temperature dependence of the luminescence quantum yield indicates the existence of 2 or 3 quenching processes with different activation energies. BR phosphorescence was not observed in the region 500-1100 nm. High degree (36%) of luminescence polarization shows that there is no homogeneous energy transfer between BR molecules, or there is a regularity in their dipole orientation. Energy migration from most carotenoids to BR was not found, but limited heterogeneous transfer between the different BR forms cannot be ruled out. The absence (or limitation) of migration indicates that there is a spatial separation of the chromophores. Data on possible participation of triplet states in the BR photoconversions are discussed.

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