Absorption and photoacoustic spectroscopies of lutein and zeaxanthin Langmuir–Blodgett films in connection with the Haidinger's brushes

Abstract

The molecular state of a single monolayer of lutein, zeaxanthin, and of a mixture of lutein and L-a-phosphatidylcholine-P-oleoyl-y-stearoyl has been investigated using absorption and photoacoustic spectroscopies. Both methods, confirmatively, reveal that the two carotenoids are mostly in a monomer state coexisting with carotenoid crystals. We observe that the absorption as well as the photoacoustic bands are red-shifted relative to the bands in solution. The absorption bands are found to peak at mean values of 440.0, 464.8, and 503.8 -t 0.5 nm for lutein, and at 452.7, 475.9, and 513.7 -t 0.5 nm for zeaxanthin. The photoacoustic peaks are situated at 444.0, 467.2, and 502.4 5 0.5 nm for lutein, and 455.4, 473.8, and 509.0 2 0.5 nm for zeaxanthin. Diluting lutein monolayer with the phospholipid results into a blue-shift of the absorption bands compared with those of the pure carotenoid monolayer and the macular pigment spectra. The results are discussed in connection with the Haidinger's brushis. It is concluded that lutein molecules might not be mixed with membrane lipids in the macular tissue, but form a monolayer protruding from the Henle fiber membranes to form the Haidinger's brushes in the macula. zeaxanthine. Lors de la dilution de la monocouche de luttine avec le phospholipide, les bandes observtes sont dtplactes vers le bleu par rapport a celles obtenues dans le spectre de la monocouche de carottno'ide pur ainsi dans celui du pigment maculeux. On discute des rtsultats en fonction des brosses de Haidinger. On en conclut que les moltcules de luttine ne sont peut Ctre pas milangees avec les lipides membranaires dans le tissu maculeux; toutefois, elles forment une rnonocouche faisant saillie par rapport aux fibres membranaires de Henle et elles conduisent a la formation des brosses de Haidinger dans la macule.[Traduit par la revue]

Carotenoids and polyterpenoids

“…, ~-~~ Much of the work involved the use of mixed monolayers of lipid (natural or synthetic lecithin, or digalactosyldiacylglycerols) with various carotenoids for studies at the air-water interface. The carotenoids that were incorporated included zeaxanthin, P-cryptoxanthin (p,P-caroten-3-01), (50), lu tein and as taxanthin (3,3'-dihydroxy-P,P-caro tene-4,4'dione), (51), in the free form or as acyl esters, and 8'-apo-Pcaroten-8'-oic acid ethyl ester (52). The molecular structures and properties of the monolayers were investigated and data such as compression isotherms, collapse surface pressures, and ejection curves were r e ~o r d e d .…”

Electron-Vibrational Spectra and Dynamics of the Lutein Molecule

“…Absorption spectra of lutein contain one broad band in the visible region. − This band has three peaks with the distance between them equal to ∼1300 cm –1 due to the vibrational splitting. , Different studies show that this band corresponds to the S 0 → S 2 transition of lutein (1A g → 1B u according to the polyenes’ electronic state classification), and there is another state (S 1 or 2A g ) in the red part of spectra. However, the S 0 → S 1 transition is optically forbidden and cannot be seen in absorption or fluorescence spectra. − It should be mentioned that some studies show that, between S 0 and S 2 states, another electronic state denoted as S* can be located.…”