Understanding Nonlinear Composition Dependency of Enantioselectivity in Chiral Separation Using Mixed Mi-celle

13 April 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Mixtures of chiral and achiral building blocks of supramolecules exhibit interesting cooperative phenomena, indicated by the nonlinear relationship between chiral properties and the mole fraction of chiral building blocks. However, the nonlinear com-position dependence of the chiral recognition capability of spherical mixed micelles is not well understood. In this work, achiral (N-dodecanoyl-glycine or N-dodecanoyl-2-methylalanine) and chiral (N-dodecanoyl-L-alanine) surfactants were studied in detail. Micellar electrokinetic chromatography found nonlinear composition dependencies of enantioselectivity. Capillary electrophoresis, circular dichroism (CD) spectroscopy, surface tension measurement, and fluorescence spectroscopy were used to investigate the following four possible mechanisms: (i) synergistic and antagonistic interactions between two different kinds of surfactants; (ii) the chiral transfer from chiral to achiral surfactant; (iii) differences in the capacity factor of surfac-tants; and (iv) enhanced cooperative chiral recognition of the chiral and achiral surfactant boundaries in the mixed micelle. Based on derived equations, the effect of (i) and (ii) was negligibly small, while (iii) and (iv) were dominant for the observed nonlinear enantioselectivity.

Keywords

chiral
surfactant
micelle
capillary electrophoresis

Supplementary materials

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Description
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Supporting Information
Description
Full experimental details, enantioselectivity versus mole frac-tion of chiral surfactant in SDGly/SDLAla system, the capaci-ty factor of SD2MeAla/SDLAla system, CD and UV spectra, Aggregation number determined by fluorescence measurement, and physical properties of the micelles.
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