OPTICAL-PROPERTIES OF THE PURPLE BACTERIUM REACTION CENTERS IMMOBILIZED IN POLYMER FILM

Reaction centres (RC) from the purple bacterium Rhodobacter sphaeroide s (strain R-24.1 and carotenoid-free mutant R-26.1) were separated and immobilized in isotropic and stretched polyvinyl alcohol (PVA) films. Absorption, fluorescence, delayed luminescence (8-300 K) and photoaco ustic spectra (PAS) of immobilized samples were measured. The RC from wild strain R-24.1 and from carotenoid-free mutant R-26.1 were differe ntly oriented in the stretched polymer film. In R-24.1 the long axis o f the RC complex was directed under some angle with respect to the per pendicular direction to the PVA film plane, whereas in R-26.1 it was a lmost perpendicular to this plane. The shapes of linear dichroism (LD) of both strains were different. Delayed luminescence (DL) bands were located in a similar wavelength range as the bacteriochlorophyll and b acteriopheophytin prompt fluorescence bands. Intensity of DL was indep endent of temperature in the 8-300 K range. The intensity of DL was ab out three time lower than that of the fluorescence. The dependence of PAS on the frequency of radiation modulation and on the phase shift be tween modulated acting radiation and measured PAS showed that part of the thermal deactivation was undergoing slowly, Intensity ratio of the slow component to the fast one and/or decay time of the slow componen t of thermal deactivation were different for various chromophores and for RC from the two strains of bacteria.