Photoinduced reductive cleavage of some chlorobenzylic compounds. New insights from comparison with electrochemically induced reactions.

The photoinduced reductive cleavage of the carbon-chlorine bond in some chlorobenzylic nitro- and cyano-substituted compounds has been studied by transient absorption spectroscopy. The influence of the nature of the electroattractive group as well as its relative position and of the mixture composition of the solvent were investigated to give new clues into the mechanisms and into the factors that control the concerted or stepwise character of the process. Experimental results have been compared with previous results obtained by electrochemical techniques on the same molecules.

Target analysis of primary photoprocesses involved in the oxyblepharismin-binding protein.

Target analysis is performed on previously published transient absorption spectra of the 200-kDa oxyblepharismin-binding protein (OBIP) thought to trigger the photophobic response of the ciliate Blepharisma japonicum. The OBIP sample is considered as heterogeneous and made of two distinct classes of chromophore-protein complexes. A so-called nonreactive class is seen to be comparable to free oxyblepharismin in organic solution.

Spectroscopic study of the chromophore--protein association and primary photoinduced events in the photoreceptor of Blepharisma japonicum.

Blepharisma japonicum is a ciliated protozoan exhibiting a strong step-up photophobic response upon illumination. The photoreceptor chromophores responsible for this response have been identified to be hypericin-like chromophores (blepharismin and oxyblepharismin), complexed to a 200 kDa non-water-soluble protein. The present work opens up new perspectives on the primary phototransduction steps of B.

Circular dichroism of the photoreceptor pigment oxyblepharismin.

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 alpha-helix content of the protein matrix.