Molecular Orientation of all-trans-β-Carotene in Spin-Coated Film and in Langmuir-Blodgett Film as Detected by Polarized Optical Absorption and Reflection Spectroscopies

Abstract

The molecular orientation and spatial arrangement of all- trans-β-carotene in a spin-coated (SC) film and in a mixed Langmuir-Blodgett (LB) film with barium stearate (1:10) were studied by the use of polarized optical absorption and reflection spectroscopies at non-normal incidences. The newly applied analyses of these spectra show that the SC film is an amorphous film with density ρ=0.835 g/cm3, refractive index n=1.38 and extinction coefficient κ=1.09 at 445 nm. Based on the axis model proposed by Schmidt and Reich [Ber. Bunsenges. Phys. Chem. 76 (1972) 1202], the angle of the molecular axis in the LB film relative to the plane of the substrate was determined to be 27°. The relative strengths of the molecular interaction of β-carotene were compared for the n-hexane solution, LB film, SC film, and single crystal. It was shown that the molecules in the LB film are weakly aggregated, although the size of the aggregate is so small that it can be identified as a `monomer'. The Davydov splitting E D of the single crystal is obtained as 170±60 cm-1.

Glyceroglycolipids Affect Uptake of Carotenoids Solubilized in Mixed Micelles by Human Intestinal Caco‐2 Cells

“…The absorption spectrum of carotenoids is known to be affected by the interaction of carotenoid molecules with a solvent and by the interaction among the carotenoid molecules themselves [16,[29][30][31][32][33][34][35][36][37][38][39][40][41]. In the present study, the λ max values of carotenoids in the NoPL micelles showed a bathochromic shift compared to those in organic solvents.…”

Acyl moieties modulate the effects of phospholipids on β‐carotene uptake by Caco‐2 cells

“…An additional spectral broadening and a partial loss of the vibrational fine structure were detected in the spectrum of 16:0,18:1-PC. Hashimoto et al (34) reported increases in the spectral bandwidth along with increases of βcarotene aggregation levels. Therefore, in the present study, part of the β-carotene molecules may have aggregated in the micelle interior, particularly when it contained 16:0,18:1-PC, delaying β-carotene desorption from these micelles.…”

“…The UV-visible absorbance spectra of carotenoids are known to change according to the interactions between the carotenoid and its surrounding environment such as solvents (21), the interior of lipoprotein particles (33), and aggregated carotenoid molecules (34,35). The λ max is proportional to solvent polarizability, and thus to its refractive index (21).…”

Natural and artificial light-harvesting systems utilizing the functions of carotenoids

“…Self-aggregation of carotenoid often takes place in aqueous organic solutions [154][155][156][157][158][159][160]. Carotenoid aggregates have also been observed in thin solid films [161][162][163] and in composite molecules [164,165]. Nevertheless, the self-assembly of fucoxanthin has not yet been reported.…”