Chromophore assignment in phycoerythrocyanin from Mastigocladus laminosus |
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Authors: | Parbel Axel Zhao Kai-Hong Breton Jacques Scheer Hugo |
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Institution: | (1) Botanisches Institut der Universität, Menzinger Str. 67, D-80638 München, Germany;(2) Academia Sinica, Institute of Photographic Chemistry, 100101 Beijing, China;(3) Department of Biochemistry and Biophysics, Institute of Life Sciences, Wuhan University, Wuhan, Hubei, 430 072, China;(4) SBE/DBCH, CEA Saclay, 91191 Gif sur Yvette, France |
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Abstract: | The component spectra (maxima of absorption, circular and linear dichroism) of individual chromophores have been assigned for phycoerythrocyanin (PEC) trimer, monomer(s), and its subunits (-PEC and -PEC) by titration with p-chloromercury-benzene-sulfonate (PCMS), linear dichroism and photochemical transformations, as well as by deconvolution using a bilin line-shape spectrum based on the -84 phycoviolobilin-chromophore in the -subunit. The level ordering PVB--84 PCB--155 PCB--84 is the same irrespective of aggregation. Two different monomers () were observed. In 4 M urea, the spectra are appropriately weighted sums of the subunit spectra, whereas in the monomer obtained in 1 M KSCN, both -chromophores are red-shifted by 4–5 nm. Formation of trimer ()_3gives considerable spectral changes: (1) the absorption is narrowed, which has been rationalized by excitonic coupling between neighbouring monomers, (2) the short wavelength part in the CD spectrum is missing and (3) a fourth band (+) at 528 in the LD spectrum appears. A deconvolution of the trimeric aggregation state using only the bilin line-shape model is not possible. |
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Keywords: | cyanobacteria energy transfer Fischerella PCC 7603 photosynthesis phycobiliprotein phycoerythrocyanin |
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