NMR and molecular modeling study, as complementary techniques to capillary electrophoresis method to elucidate the separation mechanism of linezolid enantiomers

NMR study and molecular modeling were performed to improve the level of understanding of the chiral recognition process occurring between linezolid and anionic single-isomer cyclodextrin-heptakis-(2,3-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS-beta-CD). NMR spectrometry allowed to estimate the stoichiometry of the complexes between HDAS-beta-CD and S- or R-linezolid and to determine the binding constants. The 1:1 complex stoichiometry was detected in millimolar concentrations and the mode of binding was proposed. The binding constants Ka of the complexes were of the order of 30-80 M(-1). Molecular dynamic simulations of 40ns for four complexes and calculations of binding free energies were performed. These calculations allowed determining the mode of binding of linezolid to HDAS-beta-CD and explaining the binding enantioselectivity.