In pharmacological study the separation of the enantiomers of a racemic mixture is very important because only one enantiomers of a racemic drug has useful pharmacological activities. Chiral chromatography is the most common technique for obtaining an enantiomer pure drug. The choice of the stationary phase is a crucial issue in any separation based on chiral chromatography [1]. The stationary phase should be chiral and its molecules should be easily accessible to the enantiomers. Recently, cross-linked protein crystals are suggested for the stationary phase of the chromatography columns due to their properties such as porosity and chirality. They are made of L-amino acids, therefore are chiral [2]. Also they contain pores that range from approximately 0.3-10 nm and occupy 25-75% of the crystal volume [3]. In this study, transport of a 0.5 M racemic mixture of Ibuprofen molecules inside nanopores of lysozyme protein crystal was investigated using molecular dynamic simulation (MDS) method. Ibuprofen was applied as a chiral molecule and Lysozyme protein crystal was selected as the stationary phase. This protein is a simple and known model of the cross linked protein crystals. It composed of nanopores with the diameter size ranges from 0.8-1 nm [3]. MD simulation was performed in a canonical ensemble (NVT) at 300 K for 8 ns with the time step of 2 fs. Our results from MD simulation show that lysozyme nanopores have an influential impact on the solute transport. Calculated analysis show that there is a strong interaction between ibuprofen molecules at both R- and S- form and lysozyme amino acids located on the internal surface of the crystal nanopores. These interactions cause a difficult transport for solute molecules. However, these interactions for R-form are more stronger than S-form. This stronger interaction causes less movement for R- molecules inside pores specially along the z axis. Indeed, the number of hydrogen bond and self diffusion coefficient for S-form is more than R-form. Calculated self diffusion coefficient with Einstein equation [3] for S-form is 1.92 * 10-11 m2.s-1 while this value for R-forms decreases to 1.28 *10-11 m2.s-1. Also an anisotropy diffusion behaviour was observed along the pore. These different interactions are the result of different amino acids located at the internal surface of the pores. At last, our results suggest this protein crystal as a good choice for separation of chiral ibuprofen molecules.

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