title: Molecular Properties of Astaxanthin in Water/Ethanol Solutions from Computer Simulations.
abstract: Astaxanthin (AXT) is a reference model of xanthophyll carotenoids, which is used in medicine and food industry, and has potential applications in nanotechnology. Because of its importance, there is a great interest in understanding its molecular properties and aggregation mechanism in water and mixed solvents. In this paper, we report a novel model of AXT for molecular dynamics simulation. The model is used to estimate different properties of the molecule in pure solutions and in water/ethanol mixtures. The calculated diffusion coefficients of AXT in pure water and ethanol are (3.22 ± 0.01) × 10(-6) cm(2) s(-1) and (2.7 ± 0.4) × 10(-6) cm(2) s(-1), respectively. Our simulations also show that the content of water plays a clear effect on the morphology of the AXT aggregation in water/ethanol mixture. In up to 75% (v/v) water concentration, a loosely connected network of dimers and trimers and two-dimensional array structures are observed. At higher water concentrations, AXT molecules form more compact three-dimensional structures that are preferentially solvated by the ethanol molecules. The ethanol preferential binding and the formation of a well connected hydrogen bonding network on these AXT clusters, suggest that such preferential solvation can play an important role in controlling the aggregate structure.
authors.affiliation: Jacobs University Bremen , Campus Ring 8 28759, Bremen, Germany.
authors.forename: Khadga Jung
authors.initials: KJ
authors.lastname: Karki
authors.affiliation: Department of Physics, University of Cagliari , S.P. Monserrato-Sestu Km 0.700, I-09042, Monserrato, Cagliari, Italy.
authors.forename: Susruta
authors.initials: S
authors.lastname: Samanta
authors.affiliation: School of Mathematics and Physics, University of Lincoln , Brayford Pool, LN6 7TS, Lincoln, U.K.
authors.forename: Danilo
authors.initials: D
authors.lastname: Roccatano
mesh_terms: D003198:Computer Simulation; D000431:Ethanol / Q000737:chemistry*; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D012996:Solutions; D014867:Water / Q000737:chemistry*; D024341:Xanthophylls / Q000737:chemistry
chemical_list: D012996:Solutions; D024341:Xanthophylls; D014867:Water; D000431:Ethanol; C005948:astaxanthine