Ricerche sui pigmenti fotosintetici di Gracilaria verrucosa (Huds.) Papenfuss. Dosaggio quantitativo della ficoeritrina

Abstract

Research on photosynthetic pigments from Gracilaria verrucosa (Huds.) Papenfuss. Quantitative analysis of phycoerythrin. – Among biliproteins of Rhodophycean algae, phycoerythrin is very interesting for constant distribution, in large amounts, in the different species. Phycoerythrin's extinction coefficients have been already calculated for some Bangiophycean and only two species of Rhodophycean algae. In this work we have analyzed all photosynthetic pigments and isolated pure phycoerythrin from Gracilaria verrucosa (Huds.) Papenfuss [= Gracilaria confervoides (L.) Grev.] belonging to Gigartinales. The aim of our research was to evaluate the quantitative ratio between this pigment and the others in a sistematic group for which there are only qualitative data. Phycoerythrin of Gracilaria is the R-classical type, with three absorption maxima. Average values of absorption coefficients, calculated on a large number of samples are E₁ ^%cm (565 nm) = 53.8, E₁ ^%cm (540 nm) = 48.4, E₁ ^1%cm (498 nm) = 49.1. These values are different from those obtained for R-phycoerythrin of Ceramium rubrum and B-phycoerythrin of Rhodochorton floridulum, both species belonging to Floridean algae. Our several experiments by chromatography and gel-electrophoresis process have demonstrated that the R-phycoerythrin we isolated is substantially pure. Thus we suggest that different absorption coefficient values are due either to a more complicated protein in the pigment molecule or to a different chromophore/protein ratio. This could result very interesting for the chemotaxonomic and phylogenetic aspect, but the small number of algae till now analyzed does not allow to draw any general conclusion.