Organisation of xanthophyll-lipid membranes studied by means of specific pigment antisera, spectrophotometry and monomolecular layer technique luteinversus zeaxanthin

The structure of the xanthophyll pigments lutein and zeaxanthin differs in the position of one double bond and refers to one of the ionon rings. Speci fic antibodies to zeaxanthin were used to analyse the localisation and orie ntation of these two xanthophyll pigments in lipid membranes formed with eg g yolk lecithin. Bimolecular and monomolecular layers were used. Antibody-a ntigen interaction was demonstrated and analysed by the bathochromic shift of the absorption spectra of both pigments and by the increase of light-sca ttering of the pigmented liposome suspension. It appeared that the extent o f the spectral effects accompanying the interaction of the antiserum to zea xanthin, injected to the liposome suspension which was pigmented with eithe r zeaxanthin or lutein, was different in spite of their similar molecular s tructures. The results are interpreted in terms of a localisation and distr ibution of lutein, in the hydrophobic phase of liposomes within two essenti ally different pigment pools, one oriented horizontally and the other verti cally with respect to the membrane plane. This interpretation is supported by the analysis of isotherms of the compression of monomolecular layers of lutein and zeaxanthin formed at the air-water interface and of mixed xantho phyll-lipid monolayers as well as by analysis of the penetration of antibod y proteins dissolved in the subphase into the mixed xanthophyll-lipid films .