Computational Chemical Physics Group

Exploring Nature With Computer Simulations

Molecular Properties of Astaxanthin in Water/Ethanol Solutions from Computer Simulations

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Khadga Jung KarkiSusruta Samanta, and Danilo Roccatano*

J. Phys. Chem. B, August 2016

DOI: 10.1021/acs.jpcb.6b06055

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 cm2s-1 and (2.7+/-0.4) 10-6 cm2s-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, 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.

TOC

Profile photo of Danilo Roccatano

Author: Danilo Roccatano

Danilo Roccatano received his PhD in chemistry in 1997 at the University of Rome “La Sapienza”, Italy. From 1996, he worked as a postdoc in the group of Prof. H.J.C. Berendsen at the Chemistry department of the University of Groningen in the Netherlands. In 2001, he moved back in his home country with a research associate fellowships, first at the University of Rome “La Sapienza” and later at the University of L’Aquila. In 2003, he started a position of senior research associate position in Germany at the International University Bremen. In July 2005, he was promoted to Lecturer, and, later in 2009, he got the assistant professor position in Biochemical Engineering at the same university (then renamed as Jacobs University Bremen). Since then, he is leading a computational chemistry and biochemistry group, which attracted funding and students from different Germany national research agencies (DFG, BMBF, DAAD), EU, and biotech companies (EVONIK, BASF, BRAIN). In October 2015, he started a Senior Lecturer position in the School of Mathematics and Physics of the University of Lincoln.

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