Simulation of Tyrosine Enantiomers Diffusion Through a Chitosan Membrane

FRIDA C. D. DIMARCO PALENCIA; SONIA E. BARBERIS; JUAN C. GARRO MARTINEZ; ESTEBAN G. VEGA HISSI

San Juan

Congreso; XLI Reunión Científica Anual de la Sociedad de Biología de Cuyo; 2023

Sociedad de Biología de Cuyo (SBC)

In the field of enantiomer separation, the main benefits of using a polymeric membrane are the easy scalability and repeatability of the process along with relatively low cost and easy preparation of polymeric materials. The aim of this work is the development of an extended model of a chitosan membrane to provide insights into the most predominant interactions of tyrosine enantiomers (L- and D-) with the polymer matrix that account for the differences in experimentally determined diffusion rates. The structure is made up of 64 polysaccharide chains, each consisting of 10 monomeric units, organized in an 8 x 8 matrix with an antiparallel configuration. To achieve a degree of acetylation (DA) of 20%, a random selection of β-D-glucosamine residues was N-acetylated. The free amino groups were modeled as either neutral or protonated according to the pH of 7 and the pKa of the glucosamine titratable amine group (about 6.4). Furthermore, three system configurations were constructed by placing a single tyrosine molecule randomly in the xy plane within the solvent next to the chitosan film. For each of the starting positions, tyrosine was pulled along the z-axis through the chitosan film. Two types of steered molecular dynamics (SMD) simulations were performed. Although our calculations were carried out with a crystal-like polymer configuration representing an ideal chitosan membrane, our systems act as models to explore the interactions that tyrosine enantiomers establish as they traverse the membrane. Tyrosine enantiomers present different behavior across the chitosan membrane, difference that is highlighted in SMD simulations at a constant pull force of 1000 kJ/mol/nm. D-Tyr was shown to cross the chitosan membrane more frequently compared to L-Tyr. We think that this difference arises from the stronger interactions that L-Tyr might establish with the chitosan functional groups as it moves through the membrane.