Fluorescence of chlorosomal bacteriochlorophylls in organic solvents
A.A. Zhiltsova,1 O.A. Filippova,1 E.D. Krasnova,2 D.A. Voronov,3 S.V. Patsaeva,1
1 Lomonosov Moscow State University, Faculty of Physics, Moscow, Russia
2 Lomonosov Moscow State University, Faculty of Biology, Moscow, Russia
3 Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, Russia
Abstract
Bacteriochlorophylls d and e belong to the chlorosomal bacteriochlorophylls (BChl) of green sulfur bacteria (GSB). They are in a highly aggregated state in chlorosomes – the special light harvesting complexes of the cells. Under the influence of a solvent the cell structure is destroyed, the monomeric form of the pigment is released into the solution. In addition to the change of the state of pigment molecules, their spectral properties also change. It is known that when cells are placed in an organic solvent, an absorption maxima of BChl shift by 70-80 nm to the short-wavelength region of the spectrum. There are no data about changes in the fluorescent properties of BChl d and e in the literature. In this paper, the fluorescence of chlorosomal bacteriochlorophylls in several organic solvents – acetone, methanol, ethanol, isopropanol and mixtures of acetone-methanol (7:2) and acetone-ethanol (7:2) was studied. These solvents have been mentioned in a number of practical works in microbiology and biochemistry, which determines their use in work. The wavelength of fluorescence excitation was found at which the intensity of BChl d and e radiation in solvents was maximal (425 nm), the maxima of BChl fluorescence emission at this excitation wave were determined in various solvents, hypotheses were put forward to explain the obtained patterns. It is currently not possible to choose one solvent completely suitable for extracting photosynthetic pigments of cells (due to the dependence of the extraction efficiency of lipophilic pigments (which includes BChl) on the polarity of the solvent, the species diversity of organisms, the location and orientation of the intracellular pigment, the interaction of the solvent with the membrane, etc.), then these studies are necessary for the correct interpretation of spectrophotometric data.
The work was performed using the financial support of the Theoretical Physics and Mathematics Advancement Foundation “BASIS”
Speaker
Anna Zhiltsova
Moscow State University, Faculty of Physics
Russia
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