The effect of solvent on the optical properties of myxoxanthophyll from Synechocystis sp. PCC6803

Abstract

Myxoxanthophylls (myxol 2′-glycosides) are carotenoid glycosides that occur almost exclusively in cyanobacteria. In this study, a fraction containing myxoxanthophylls was isolated from the model cyanobacterium Synechocystis PCC 6803. An HPLC and LC/MS-based analysis revealed that in this organism myxoxanthophyll is present as a mixture of geometrical isomers, with a dominating all-trans form. The absorption maxima as observed in solutions of isolated myxoxanthophyll are amenable to solvent properties, displaying solvent-dependent shifts in the visible region (solvatochromism). In organic solvents, myxoxanthophyll shows the absence of any specific solvent–solute interactions, as the energy of its electronic transitions increases only with solvent polarizability. In contrast, an aqueous environment promotes intermolecular interactions, which are directly manifested as changes in the absorption spectra of myxoxanthophyll. The biological significance of the observed changes in chemical and optical properties of myxoxanthophyll molecules remains to be elucidated.