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Circular Dichroism of the Photoreceptor Pigment Oxyblepharismin
Author(s) -
Pieroni Osvaldo,
Plaza Pascal,
Mahet Mathilde,
Angelini Nicola,
Checcucci Giovanni,
Malatesta Manuela,
Martin Monique M.,
Lenci Francesco
Publication year - 2005
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/2005-04-28-rn-504
Subject(s) - chromophore , circular dichroism , pigment , chemistry , enantiomer , molecule , matrix (chemical analysis) , cotton effect , crystallography , stereochemistry , photochemistry , organic chemistry , chromatography
ABSTRACT Circular dichroism (CD) was used to study the structure of oxyblepharismin (OxyBP), the photoreceptor chromophore for the photophobic response of the blue form of Blepharisma japonicum. Both the chromophore associated to its native protein and the free chromophore in ethanol solution were investigated. CD spectra in the far‐UV range indicate that OxyBP induces a slight increase in the α‐helix content of the protein matrix. CD spectra in the near‐UV and visible region of the spectrum show that OxyBP adopts a chiral conformation with a preferential geometry not only when associated to its protein matrix, but also when isolated and dissolved in ethanol. This experimental result is related to the existence of a high‐energy interconversion barrier between two enantiomeric structures of the molecule and discussed on the basis of an asymmetric biosynthesis of its precursor, blepharismin.