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2. Optical properties of the purpie bacterium reaction centres immobilized in polymer film
- Creator:
- Frackowiak, D., Dudkowiak, A., Cegielski, R., Planner, A., and Schulz, C.
- Format:
- Type:
- model:internalpart and TEXT
- Subject:
- absorption spectrum, bacteriochlorophyll, carotenoid-free mutant, delayed luminescence, fluorescence spectrum, isotropic and stretched films, linear dichroism, photoacoustic spectrum, polyvinyl alcohol film, and Rhodohacter sphaeroides
- Language:
- Multiple languages
- Description:
- Reaction centres (RC) from the purpie bacterium Rhodohacter sphaeroides (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 photoacoustic spectra (PAS) of immobilized samples were measured. The RC from wild strain R-24.1 and ffom carotenoid-free mutant R-26.1 were differently oriented in the stretched polymer film. In R-24.1 the long axis of the RC complex was directed under some angle with respect to the perpendicular direction to the PVA film plane, whereas in R-26.1 it was almost 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 bacteriopheophytin prompt fluorescence bands. Intensity of DL was independent of temperature in the 8-300 K range. The intensity of DL was about three time lower than that of the fluorescence. The dependence of PAS on the frequency of radiation modulation and on the phase shift between 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 component of thermal deactivation were different for various chromophores and for RC ffom the two strains of bacteria.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
3. Paths of deactivation of excited bacteriochlorophyll с in the green photosynthetic bacterium Prosthecochloris aestuarii
- Creator:
- Dudkowiak, A., Cegielski, R., Ptak, A., Planner, A., Chrzumnicka, E., Hanyž, I., and Frackowiak, D.
- Format:
- Type:
- model:internalpart and TEXT
- Language:
- Multiple languages
- Description:
- Absorption , fluorescence, delayed emission and photoacoustic spectra were obtained for the green photosynthetic bacterium. Whole cells incorporated in fluid (culture medium, viscous solution of polyvinyl alcohol, glycol) and rigid (isotropic and stretched polyvinyl alcohol film) media were investigated. The polarized absorption spectra of the stretched polyvinyl alcohol sample showed that the Qy transition moments of chlorosomal bacteriochlorophyll с was almost parallel to the film axis. Bacteriochlorophyll (BChl) с degradation occurred in some of the samples during prolonged storage and as a result a pigment absorbing at 670 nm, which was disaggregated BChl с or/and bacteriopheophytin c, was formed. This pigment was unoriented in stretched polyvinyl alcohol. The fluorescence spectrum of native cells can be analyzed using three Gaussian components at 754, 781 and 813 pm. The first component seems to be related to BChl с aggregates and the others to BChl a complexes. The time-resolved delayed luminescence spectra showed that practically all the complexes of green bacteria exhibited delayed emission but the decay times and intensities were different for the different complexes. In the photoacoustic spectra two maxima of the chlorosomal BChl с forms were well resolved and located at 748 and 765 nm. The photoacoustic maximum at 830 nm was probably related to the reaction centre (RC). In the Soret band the largest peak of the photoacoustic spectra was observed at 473 nm which showed that carotenoids absorbing in this range were losing more excitation by heat. The BChl с aggregates attached to chlorosome rods exhibited a peak at 446 nm. The efficient thermal deactivation also showed a BChl a located in RC (peak at 846 nm) and long-wavelength BChl a antenna complexes with a deactivation peak at 884 nm.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
4. Photothermal spectra of thylakoids isolated from cucumber cotyledons at various stages of greening
- Creator:
- Waloszek, A., Więckowski, S., Planner, A., Boguta, A., and Frąckowiak, D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Cucumis sativus, laser-induced optoacoustic spectra, and photoacoustic steady state spectra
- Language:
- Multiple languages
- Description:
- The character of interaction between carotenoids (Cars) and chlorophylls (Chls) in thylakoids isolated from cucumber cotyledons at three stages of greening (3, 6, and 24 h of irradiation with 120 µmol m-2 s-1) was studied. The shapes of the steady state photoacoustic spectra were changed with the change in time of greening and with the frequency of radiation modulation. The shapes show that changes not only in the contents of various pigments but also in pigment interactions with surrounding occur and that processes of thermal deactivation characterised by different kinetics take place. Slow processes of thermal deactivation are in most cases due to deactivation of triplet states. Long living triplet states are very often engaged in photochemical reactions that can destroy the tissue. Analysis of the time-resolved photothermal spectra shows that at later stage of greening, the chlorophyll (Chl) molecules are better shielded against photo-destruction because Cars more efficiently quench their triplet states. The yield of formation of the pigment triplet states measured by the time resolved photothermal method, always at the same energy absorbed by pigment mixture, declined during sample greening. The decay time of the slow component of pigment thermal deactivation, due predominantly to deactivation of the triplet state of Chl, decreases with the increase of time of greening from 6.2 µs for the 3-h sample to 1.5 µs for the 24 h sample. The energy taken by Cars from Chls is dissipated into heat, therefore the steady state and quick thermal deactivation values increased during the greening process. The Cars/Chls ratio in the thylakoids decreased during greening approximately 2 fold. Hence at a later phase of greening the Cars can quench the triplet states of Chls more efficiently than at an earlier phase of greening. and A. Waloszek ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
5. Polarized photoacoustic spectra of the cyanobacterium Synechococcus oriented in polymer film
- Creator:
- Planner, A., Hara, M., Miyake, J., Waszkowiak, A., Klaczyńska, K., and Frąckowiak, D.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- biliproteins, carotenoids, chlorophyll, polyvinyl alcohol films, and transition moment orientation
- Language:
- Multiple languages
- Description:
- Photoacoustic spectra (PAS) were obtained for the cyanobacterium Synechococcus (Anacystis nidulans) cells embedded in isotropic and stretched polyvinyl alcohol films. The polarized radiation with the electric vector changing in 30° intervals with respect to given direction in a sample plane was used. Two cyanobacterium strains, one with very low biliprotein content, second with normal amount of biliproteins were investigated. The polarized absorption and fluorescence spectra were also measured. Conclusions were drawn about the thermal deactivation occurring in differently oriented pools of chromophores and about mutual orientation of their transition moments. Thermal deactivation in carotenoids (Cars) of both strains was different. The ratio of Car thermal deactivation to the thermal deactivation of chlorophyll (Chl) was higher in cyanobacteria with lower content of biliproteins than in the strain with normal amount of these complexes. Hence biliproteins can play the role in excitation energy transfer from Cars to Chls. For complex biological samples, polarized PAS can be a more sensitive method to investigate the directions of the absorption transition moments than the widely used polarized absorption spectra. and A. Planner ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
6. Properties of photosynthetic bacteria in anisotropic rigid matrix and in suspension
- Creator:
- Planner, A., Hara, M., Stachowiak, Z., and Miyake, J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Anabaena variabilis, cyanobacteria, fluorescence microscope photographs, orientation, polarized spectra, polyvinyl alcohol film, purple bacteria, radiation scattering, Rhodospirillum rubrum, and Synechococcus
- Language:
- Multiple languages
- Description:
- The photosynthetic bacteria (Rhodospirillum rubrum, Synechococcus and Anabaena variabilis) as well as their fragments embedded in isotropic and anisotropic polymer film were investigated. The orientation of photosynthetic pigments inside these organisms was compared, on the basis of the polarised absorption and fluorescence spectra, with the macroscopic orientation of investigated objects seen under microscope. The anisotropy of fluorescence was much higher than anisotropy of absorption. It showed strong influence of the photoselection by polarised radiation on the various bacterial chromophores exhibiting different orientations in the cells and various yields of fluorescence. The dimensions of cells were investigated on the basis of their photographs and by the scattering of the monochromatic radiation. and A. Planner ... [et al.].
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public