Jianchao Liang1, Yanping Fan1, Zhongqiao Hu2, Jianwen Jiang3, and Raj Rajagopalan4. (1) National University of Singapore and The Singapore-MIT Alliance, Singapore, 117576, Singapore, (2) Chemical and Biological Engineering, National University of Singapore, Singapore, Singapore, (3) Chemical land Biological Engineering, National University of Singapore, Singapore, Singapore, (4) Chemical and Biomolecular Engineering, National University of Singapore, Kent Ridge, Singapore, Singapore
Chirality is ubiquitous in living organisms, as nature has evolved to favor one “handedness” over the other. Many pharmaceutically important drugs are racemic mixtures of chiral enantiomers. Clinical use of an improper enantiomer may cause death; therefore, it is important to separate enantiomers before use. Here, a molecular simulation study is presented for the chiral separation of L/D-tryptophan aqueous mixture by â-cyclodextrin film. Consistent with experimental measurements, D-tryptophan transports more rapidly than L-tryptophan. The chiral selectivity depends on the number density of â-cyclodextrin in the film and on the flow rate of the solution through the film. A slow flow rate is found to give relatively larger separation efficiency. The mechanism responsible for the enantio-discrimination is explored at the molecular scale including the preferential binding and the intermolecular forces between the analyte molecule and â-cyclodextrin. The estimated binding energy is stronger between L-tryptophan and â-cyclodextrin, which gives rise to the observed chiral separation.