Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes

Chlorosomes are light-harvesting complexes of green photosynthetic bacteria. Chlorosomes contain bacteriochlorophyll (BChl) c, d, or e aggregates that exhibit strong excitonic coupling. The short-range order, which is responsible for the coupling, has been proposed to be augmented by pigment arrange...

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Autores: Arellano, Juan B., Torkkeli, Mika, Tuma, Roman, Laurinmäki, Pasi A., Melo, Thor Bernt, Ikonen, Teemu P., Butcher, Sarah J., Serimaa, Ritva E., Psencik, Jakub
Tipo de recurso: artículo
Fecha de publicación:2008
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/3151
Acceso en línea:http://hdl.handle.net/10261/3151
Access Level:acceso abierto
Palabra clave:Chlorosomes
Lamellar aggregates
Hexanol
Bacteriochlorophyll
Chlorobium tepidum
Order-disorder transitions
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spelling Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum ChlorosomesArellano, Juan B.Torkkeli, MikaTuma, RomanLaurinmäki, Pasi A.Melo, Thor BerntIkonen, Teemu P.Butcher, Sarah J.Serimaa, Ritva E.Psencik, JakubChlorosomesLamellar aggregatesHexanolBacteriochlorophyllChlorobium tepidumOrder-disorder transitionsChlorosomes are light-harvesting complexes of green photosynthetic bacteria. Chlorosomes contain bacteriochlorophyll (BChl) c, d, or e aggregates that exhibit strong excitonic coupling. The short-range order, which is responsible for the coupling, has been proposed to be augmented by pigment arrangement into undulated lamellar structures with spacing between 2 and 3 nm. Treatment of chlorosomes with hexanol reversibly converts the aggregated chlorosome chlorophylls into a form with spectral properties very similar to that of the monomer. Although this transition has been extensively studied, the structural basis remains unclear due to variability in the obtained morphologies. Here we investigated hexanol-induced structural changes in the lamellar organization of BChl c in chlorosomes from Chlorobium tepidum by a combination of X-ray scattering, electron cryomicroscopy, and optical spectroscopy. At a low hexanol/pigment ratio, the lamellae persisted in the presence of hexanol while the short-range order and exciton interactions between chlorin rings were effectively eliminated, producing a monomer-like absorption. The result suggested that hexanol hydroxyls solvated the chlorin rings while the aliphatic tail partitioned into the hydrophobic part of the lamellar structure. This partitioning extended the chlorosome along its long axis. Further increase of the hexanol/pigment ratio produced round pigment-hexanol droplets, which lost all lamellar order. After hexanol removal the spectral properties were restored. In the samples treated under the high hexanol/pigment ratio, lamellae reassembled in small domains after hexanol removal while the shape and long-range order were irreversibly lost. Thus, all the interactions required for establishing the short-range order by self-assembly are provided by BChl c molecules alone. However, the long-range order and overall shape are imposed by an external structure, e.g., the proteinaceous chlorosome baseplate.This study was supported by the Spanish Ministry of Science and Education (Grant No. BFU2004-04914-C02-02 to J.B.A.), the Academy of Finland (Research Fellowship No. 1118462 to R.T.), the Czech Ministry of Education, Youth and Sports and Czech Science Foundation (Projects Nos. MSM0021620835 and 206/05/2739 to J.P.). Electron microscopy was carried out in the Electron Microscopy Unit of the Institute of Biotechnology, University of Helsinki.Peer reviewedAmerican Chemical Society200820082008info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_650118673 bytesimage/gifhttp://hdl.handle.net/10261/3151reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Ingléshttp://pubs.acs.org/doi/abs/10.1021/la703024einfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/31512026-05-22T06:33:51Z
dc.title.none.fl_str_mv Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
title Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
spellingShingle Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
Arellano, Juan B.
Chlorosomes
Lamellar aggregates
Hexanol
Bacteriochlorophyll
Chlorobium tepidum
Order-disorder transitions
title_short Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
title_full Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
title_fullStr Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
title_full_unstemmed Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
title_sort Hexanol-Induced Order-Disorder Transitions in Lamellar Self-Assembling Aggregates of Bacteriochlorophyll c in Chlorobium tepidum Chlorosomes
dc.creator.none.fl_str_mv Arellano, Juan B.
Torkkeli, Mika
Tuma, Roman
Laurinmäki, Pasi A.
Melo, Thor Bernt
Ikonen, Teemu P.
Butcher, Sarah J.
Serimaa, Ritva E.
Psencik, Jakub
author Arellano, Juan B.
author_facet Arellano, Juan B.
Torkkeli, Mika
Tuma, Roman
Laurinmäki, Pasi A.
Melo, Thor Bernt
Ikonen, Teemu P.
Butcher, Sarah J.
Serimaa, Ritva E.
Psencik, Jakub
author_role author
author2 Torkkeli, Mika
Tuma, Roman
Laurinmäki, Pasi A.
Melo, Thor Bernt
Ikonen, Teemu P.
Butcher, Sarah J.
Serimaa, Ritva E.
Psencik, Jakub
author2_role author
author
author
author
author
author
author
author
dc.subject.none.fl_str_mv Chlorosomes
Lamellar aggregates
Hexanol
Bacteriochlorophyll
Chlorobium tepidum
Order-disorder transitions
topic Chlorosomes
Lamellar aggregates
Hexanol
Bacteriochlorophyll
Chlorobium tepidum
Order-disorder transitions
description Chlorosomes are light-harvesting complexes of green photosynthetic bacteria. Chlorosomes contain bacteriochlorophyll (BChl) c, d, or e aggregates that exhibit strong excitonic coupling. The short-range order, which is responsible for the coupling, has been proposed to be augmented by pigment arrangement into undulated lamellar structures with spacing between 2 and 3 nm. Treatment of chlorosomes with hexanol reversibly converts the aggregated chlorosome chlorophylls into a form with spectral properties very similar to that of the monomer. Although this transition has been extensively studied, the structural basis remains unclear due to variability in the obtained morphologies. Here we investigated hexanol-induced structural changes in the lamellar organization of BChl c in chlorosomes from Chlorobium tepidum by a combination of X-ray scattering, electron cryomicroscopy, and optical spectroscopy. At a low hexanol/pigment ratio, the lamellae persisted in the presence of hexanol while the short-range order and exciton interactions between chlorin rings were effectively eliminated, producing a monomer-like absorption. The result suggested that hexanol hydroxyls solvated the chlorin rings while the aliphatic tail partitioned into the hydrophobic part of the lamellar structure. This partitioning extended the chlorosome along its long axis. Further increase of the hexanol/pigment ratio produced round pigment-hexanol droplets, which lost all lamellar order. After hexanol removal the spectral properties were restored. In the samples treated under the high hexanol/pigment ratio, lamellae reassembled in small domains after hexanol removal while the shape and long-range order were irreversibly lost. Thus, all the interactions required for establishing the short-range order by self-assembly are provided by BChl c molecules alone. However, the long-range order and overall shape are imposed by an external structure, e.g., the proteinaceous chlorosome baseplate.
publishDate 2008
dc.date.none.fl_str_mv 2008
2008
2008
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
format article
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/3151
url http://hdl.handle.net/10261/3151
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv http://pubs.acs.org/doi/abs/10.1021/la703024e
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 18673 bytes
image/gif
dc.publisher.none.fl_str_mv American Chemical Society
publisher.none.fl_str_mv American Chemical Society
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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