Chiral separation in modified silica nanotube membranes: A molecular simulation study

Novel functionalized nanotube membranes were recently developed and used to efficiently sep. a chiral drug from its racemic mixt. Enantiomeric sepn. in these materials strongly relates to modifier choices and the interplay with the nanopore confinement and substrate-modifier interactions. By mol. simulations probably the enantioselectivity of such membranes can should be improved in a bio-inspired way. The authors use mol. dynamics simulations to evaluate the capability of a modified silica nanotube for enantiomeric sepn. of two amino acids, R- and S-2-phenylglycine. This smart nanotube is functionalized as an artificial protein channel in cell membranes. The biomimicry was performed through attaching functional residues (Arg, Glu, Asp) into the nanotube. Simulations indicate that the selective transport of one of the enantiomers (S-) inside the modified channel is strongly affected by presence of a special electrostatic field inside the channel. The mechanism of enantioselective passage depends on the internal degrees of freedom of the attached residues and interactions of phenylglycine mols. with these residues. The translational-rotational motion of chiral mols. as well as their av. dipole orientation is responsible for selective chiral transport inside the nanotube. It is remarkable how configuration of the immobilized residues enhances the enantiomeric sepn. of the functionalized nanotube. As an immediate application, this study would help the authors design more efficient, nature-inspired selective chiral membranes that are able to sep. enantiomers of chiral species