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Abstract
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Precise quantum mechanical studies, both in gas phase and in aqueous medium, are performed with the aim to analyse the conformational equilibria, to find the most stable equilibrium structure and to define the nature of the molecular orbitals, fundamental to explain Curcumin binding characteristic. Our theoretical calculations, both in gas phase and in aqueous medium, confirm that the enol- keto form is more stable than the di-keto one. Enol- keto form result the most stable, independently on solvent (water) effect. The computed ionization potential and electron affinity show that curcumin has a low molecular hardness and thus a tendency to readily deprotonate to form curcumin deprotonated anion, which is stabilized by extension of conjugation. Also, the curcumin-curcumin aggregation was studied by molecular dynamics simulation in the aqueous media and in the presence of single-walled carbon nanotube (SWCNT). The value of 22.7 KJ.mol-1 was computed for hydration free energy of curcumin. This relatively high value implied a hydrophobic nature for curcumin in a consistent manner with aggregated structures predicted by MD simulations. Over the last decades, an interest has arisen in investigating the interactions of different protein molecules with metal oxide nanoparticles. The molecular adsorption of curcumin molecules on the photocatalyst titanium dioxide (TiO2) is such a process. Moreover, this process is potentially efficient and suitable for industrial applications. A step toward making this process more operative is to modify TiO2 structures by Nitrogen doping. In present work, density functional theory calculations were carried out to investigate curcumin adsorption on undoped and N-doped TiO2 anatase nanoparticles in order to fully exploit the potential capabilities of these particles in sensing and applications. The unit cell of TiO2 anatase has been geometrically optimized to calculate the lattice constants, and the adsorption of gas molecule was modeled by
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