Electron Magnetic Resonance of the chlorosomes from green sulfur bacterium Chlorobium tepidum
| Autor: | P. D. Gerola, C. Vannini, Louis-Claude Brunel, Giovanni Giacometti, Donatella Carbonera, Anna Lisa Maniero, Alberto Vianelli |
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| Jazyk: | angličtina |
| Rok vydání: | 1998 |
| Předmět: |
biology
chemistry.chemical_element Chlorosome macromolecular substances Photochemistry biology.organism_classification Sulfur Fluorescence EPR spectroscopy ODMR triplet states Carotenoids Photoexcitation Pigment Chlorobium tepidum chemistry visual_art visual_art.visual_art_medium Molecule Singlet state |
| Zdroj: | Photosynthesis: Mechanisms and Effects ISBN: 9780792355472 ResearcherID |
| Popis: | Chlorosomes are the main antenna system of the green sulfur bacterium Chl. tepidum. They contain BChlc assembled into rodlike elements as oligomers. A smaller number of BChla molecules is complexed with proteins in a baseplate assembly. The pigment composition of chlorosomes is principally Bchlc while the relative amount of Bchla is about 1%. Chlorobactene is the major carotenoid (molar ratio 1:10 with respect to the Bchl). We used both FDMR and ADMR in zero field to detect triplets formation under photoexcitation of isolated chlorosomes with the aim of throwing light on energy transfer processes and pigment interactions. Preliminary ESR experiments at different microwave frequencies (9÷300 GHz) have been done, after chemical oxidation of the chlorosomes, using the cation as a tool to investigate the pigment organization. FDMR of whole cells and chlorosomes of Chi. phaeobacteroides and Chi. limicola has been previously reported [1] and several triplet species have been detected and assigned to BChla, carotenoids, and BChle (or c). FDMR of BChl c triplet states in whole cells of Chi. tepidum has also been reported [2] and compared to monomeric BChlc triplet. In this work we perform FDMR detecting the fluorescence changes selectively on the BChlc and a emission bands. Microwaves induced absorption gives the triplet minus singlet (TS) spectra of the different triplet states observed by FDMR and allows the assignment to specific pigments. |
| Databáze: | OpenAIRE |
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