APTAMERS FOR SEPARATION OF ENANTIOMERS

Three general strategies can be described for enantioselective methods using CSs (Erancotte, 2001). The first is to adapt the solute to a particular CS for 

Aptamers in Bioanalysis, Edited by Marco Mascini Copyright 2009 John Wiley Sons, Inc. 

Althongh in most cases the aptamers were not selected for enantioselective binding, efficient monitoring of the selection procedure has often permitted very high specificity, exemplified by the ability of the aptamer to bind the target stereospecifically. As hypothesized by Eamulok and co-workers (Geiger et al., 

3 IMMOBILIZED APTAMERS FOR ENANTIOMERIC SEPARATION BY LIQUID CHROMATOGRAPHY 

Nncleic acid aptamers were first exploited by our group for use in target-specific chiral separations by EC. Immobilized DNA, RNA and l-RNA (spiegelmer) oligonucleotides have been nsed snccessfnlly for the separation of enantiomers of various compounds. Table 10.1 snmmarizes the aptamer-based CSPs reported to date. 

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The nse of aptamers for the separation, pnriflcation, and quantification of analytes in chromatography, electrochromatography, and capillary electrophoresis techniqnes in general is described in detail and with examples by Ravelet et al. (2006). DNA and RNA aptamers have been nsed for the separation and purification of proteins and the separation of small molecnles and enantiomers. In capillary electrophoresis, aptamers are nsed primarily for the separation of species and the characterization of affinity interactions. Ravelet et al. (2006) state the hnge potential of these molecular tools in the separation science field. However, for big separation units, a large amonnt of aptamer is necessary, making it more expensive than other separation materials. Therefore, the nse of aptamers for separation units is limited primarily to miniatnrized systems. 

The chirality of DNA was applied to selective separation. A DNA aptamer as a new target-specific chiral selector for HPLC was investigated by Michaud et al. [119,120]. They showed that a tailor-made chiral stationary phase based on a DNA aptamer with known stereospecific binding for the D-enantiomer of the oligopeptide, arginine-vasopressin, exhibits enantioselectivity between the d- and L-peptides. This DNA-based target-specific aptamer chiral stationary phase provides a powerful tool for the resolution of small (bioactive) molecule enantiomers. 

Abstract Target-specific chiral selectors, which are characterized by a predictable elution order depending on the target enantiomer empioyed for the selection of the chirai selector, have recently received much attention in the enantioselective analysis fieid. In this context, bioaffinity-based molecular recognition toois such as nucleic acid aptamers have notabiy demonstrated very attractive features for the chiral discrimination of active moiecuies. In this chapter, the enantioseiective properties of aptamer chiral selectors and the major factors that control and modulate the liquid chromatography and capillary electrophoresis enantiomer separation are addressed. 

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