Affinity capillary electrophoresis analyte interactions

Affinity capillary electrophoresis is an electrophoretic mode that takes advantage of the specific interactions of receptors, antibodies, or ligands with the analyte. In contrast to other CE modes, ACE is not dedicated to general analysis, but rather is focused on measuring molecular interactions of the solute with specific receptors. 

Capillary affinity electrophoresis (CAE) or affinity capillary electrophoresis (ACE) — An electrophoretic separation technique (- electrophoresis), in which -> analytes are separated in a capillary, with the -> supporting (background) electrolyte containing substances capable of specific, often biospecific, interactions with the analytes. Ref [i] Riekkola ML, Jonsson jA, Smith RM (2004) Pure Appl Chem 76 443... 

Affinity capillary electrophoresis (ACE) constitutes a versatile microana-lytical technique that allows the estimation of affinity constants of analytes through the study of interactions such as protein-hgand, protein-antibody, and antibody-antigen. In ACE, PF techniques (whose optimization is not an easy task) can also be used to minimize the amount of sample needed. Chemometric methodology has also been applied for the optimization of the PF technique in ACE. 

Anions and uncharged analytes tend to spend more time in the buffered solution and as a result their movement relates to this. While these are useful generalizations, various factors contribute to the migration order of the analytes. These include the anionic or cationic nature of the surfactant, the influence of electroendosmosis, the properties of the buffer, the contributions of electrostatic versus hydrophobic interactions and the electrophoretic mobility of the native analyte. In addition, organic modifiers, e.g. methanol, acetonitrile and tetrahydrofuran are used to enhance separations and these increase the affinity of the more hydrophobic analytes for the liquid rather than the micellar phase. The effect of chirality of the analyte on its interaction with the micelles is utilized to separate enantiomers that either are already present in a sample or have been chemically produced. Such pre-capillary derivatization has been used to produce chiral amino acids for capillary electrophoresis. An alternative approach to chiral separations is the incorporation of additives such as cyclodextrins in the buffer solution. 

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. 

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