Organization of the pigment molecules in the chlorophyll a/c light-harvesting complex of Pleurochloris meiringensis (xanthophyceae). Characterization with circular dichroism and absorbance spectroscopy

C. Büchel, G. Garab

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29 Citations (Scopus)

Abstract

By the aid of circular dichroism (CD), absorbance and fluorescence spectroscopy, we studied the molecular organization of the pigment molecules in cells, isolated chloroplasts and the chlorophyll a/c light-harvesting complex (LHC) associated with photosystem II of the chlorophyll c-containing alga, Pleurochloris meiringensis. In cells and chloroplasts, similarly to higher plant chloroplasts, a (+)693 nm CD band accompanied by a tail outside the absorbance indicated a long-range chiral organization of the chlorophyll molecules. The LHCII of these algae exhibited an intense negative CD band at 679 nm. However, in contrast to the chlorophyll a/b LHCII of higher plants, where the intense, non-conservative (-)684 nm band has been shown to be associated with long-range chiral organization of the macro-aggregates, the intense, non-conservative (-)679 nm band in the chlorophyll a/c LHC originated from the non-aggregated form of the complexes. In sharp contrast to the trimers or monomers of the chlorophyll a/b LHCII, in the chtorophyll a/c LHC no split excitonic CD bands could be detected in the red spectral region, thus CD provided no indication for the occurence of excitonic interactions among the Q(y) transition dipoles of the chlorophyll molecules. Gaussian analysis of the absorbance and CD bands showed that the (-)679 nm CD signal is given rise by a small number of long-wavelength absorbing chlorophyll a molecules. Data obtained with LHC treated with low concentrations of acetone or digitonin strongly suggest a specific binding site of chlorophyll a to the protein, which upon binding a chlorophyll a molecule induces a bathochromic shift and asymmetry in the electronic structure of the molecule. These results and literature data strongly suggest that the organization of the pigment molecules in chlorophyll a/c antenna complexes is significantly different from the organization of the chlorophyll a/b complexes of green algae and higher plants.

Original languageEnglish
Pages (from-to)118-124
Number of pages7
JournalJournal of Photochemistry and Photobiology, B: Biology
Volume37
Issue number1-2
DOIs
Publication statusPublished - Jan 1997

Fingerprint

Xanthophyceae
circular dichroism spectroscopy
light harvesting complex
Dichroism
chlorophylls
Chlorophyll
Circular Dichroism
pigments
Pigments
absorbance
dichroism
spectroscopy
Spectrum Analysis
Spectroscopy
chlorophyll
Light
Molecules
molecules
Chloroplasts
Algae

Keywords

  • Algae
  • Carotenoids
  • Light-harvesting complex II
  • Photosynthesis

ASJC Scopus subject areas

  • Plant Science
  • Bioengineering
  • Physical and Theoretical Chemistry

Cite this

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title = "Organization of the pigment molecules in the chlorophyll a/c light-harvesting complex of Pleurochloris meiringensis (xanthophyceae). Characterization with circular dichroism and absorbance spectroscopy",
abstract = "By the aid of circular dichroism (CD), absorbance and fluorescence spectroscopy, we studied the molecular organization of the pigment molecules in cells, isolated chloroplasts and the chlorophyll a/c light-harvesting complex (LHC) associated with photosystem II of the chlorophyll c-containing alga, Pleurochloris meiringensis. In cells and chloroplasts, similarly to higher plant chloroplasts, a (+)693 nm CD band accompanied by a tail outside the absorbance indicated a long-range chiral organization of the chlorophyll molecules. The LHCII of these algae exhibited an intense negative CD band at 679 nm. However, in contrast to the chlorophyll a/b LHCII of higher plants, where the intense, non-conservative (-)684 nm band has been shown to be associated with long-range chiral organization of the macro-aggregates, the intense, non-conservative (-)679 nm band in the chlorophyll a/c LHC originated from the non-aggregated form of the complexes. In sharp contrast to the trimers or monomers of the chlorophyll a/b LHCII, in the chtorophyll a/c LHC no split excitonic CD bands could be detected in the red spectral region, thus CD provided no indication for the occurence of excitonic interactions among the Q(y) transition dipoles of the chlorophyll molecules. Gaussian analysis of the absorbance and CD bands showed that the (-)679 nm CD signal is given rise by a small number of long-wavelength absorbing chlorophyll a molecules. Data obtained with LHC treated with low concentrations of acetone or digitonin strongly suggest a specific binding site of chlorophyll a to the protein, which upon binding a chlorophyll a molecule induces a bathochromic shift and asymmetry in the electronic structure of the molecule. These results and literature data strongly suggest that the organization of the pigment molecules in chlorophyll a/c antenna complexes is significantly different from the organization of the chlorophyll a/b complexes of green algae and higher plants.",
keywords = "Algae, Carotenoids, Light-harvesting complex II, Photosynthesis",
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year = "1997",
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T1 - Organization of the pigment molecules in the chlorophyll a/c light-harvesting complex of Pleurochloris meiringensis (xanthophyceae). Characterization with circular dichroism and absorbance spectroscopy

AU - Büchel, C.

AU - Garab, G.

PY - 1997/1

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N2 - By the aid of circular dichroism (CD), absorbance and fluorescence spectroscopy, we studied the molecular organization of the pigment molecules in cells, isolated chloroplasts and the chlorophyll a/c light-harvesting complex (LHC) associated with photosystem II of the chlorophyll c-containing alga, Pleurochloris meiringensis. In cells and chloroplasts, similarly to higher plant chloroplasts, a (+)693 nm CD band accompanied by a tail outside the absorbance indicated a long-range chiral organization of the chlorophyll molecules. The LHCII of these algae exhibited an intense negative CD band at 679 nm. However, in contrast to the chlorophyll a/b LHCII of higher plants, where the intense, non-conservative (-)684 nm band has been shown to be associated with long-range chiral organization of the macro-aggregates, the intense, non-conservative (-)679 nm band in the chlorophyll a/c LHC originated from the non-aggregated form of the complexes. In sharp contrast to the trimers or monomers of the chlorophyll a/b LHCII, in the chtorophyll a/c LHC no split excitonic CD bands could be detected in the red spectral region, thus CD provided no indication for the occurence of excitonic interactions among the Q(y) transition dipoles of the chlorophyll molecules. Gaussian analysis of the absorbance and CD bands showed that the (-)679 nm CD signal is given rise by a small number of long-wavelength absorbing chlorophyll a molecules. Data obtained with LHC treated with low concentrations of acetone or digitonin strongly suggest a specific binding site of chlorophyll a to the protein, which upon binding a chlorophyll a molecule induces a bathochromic shift and asymmetry in the electronic structure of the molecule. These results and literature data strongly suggest that the organization of the pigment molecules in chlorophyll a/c antenna complexes is significantly different from the organization of the chlorophyll a/b complexes of green algae and higher plants.

AB - By the aid of circular dichroism (CD), absorbance and fluorescence spectroscopy, we studied the molecular organization of the pigment molecules in cells, isolated chloroplasts and the chlorophyll a/c light-harvesting complex (LHC) associated with photosystem II of the chlorophyll c-containing alga, Pleurochloris meiringensis. In cells and chloroplasts, similarly to higher plant chloroplasts, a (+)693 nm CD band accompanied by a tail outside the absorbance indicated a long-range chiral organization of the chlorophyll molecules. The LHCII of these algae exhibited an intense negative CD band at 679 nm. However, in contrast to the chlorophyll a/b LHCII of higher plants, where the intense, non-conservative (-)684 nm band has been shown to be associated with long-range chiral organization of the macro-aggregates, the intense, non-conservative (-)679 nm band in the chlorophyll a/c LHC originated from the non-aggregated form of the complexes. In sharp contrast to the trimers or monomers of the chlorophyll a/b LHCII, in the chtorophyll a/c LHC no split excitonic CD bands could be detected in the red spectral region, thus CD provided no indication for the occurence of excitonic interactions among the Q(y) transition dipoles of the chlorophyll molecules. Gaussian analysis of the absorbance and CD bands showed that the (-)679 nm CD signal is given rise by a small number of long-wavelength absorbing chlorophyll a molecules. Data obtained with LHC treated with low concentrations of acetone or digitonin strongly suggest a specific binding site of chlorophyll a to the protein, which upon binding a chlorophyll a molecule induces a bathochromic shift and asymmetry in the electronic structure of the molecule. These results and literature data strongly suggest that the organization of the pigment molecules in chlorophyll a/c antenna complexes is significantly different from the organization of the chlorophyll a/b complexes of green algae and higher plants.

KW - Algae

KW - Carotenoids

KW - Light-harvesting complex II

KW - Photosynthesis

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