RESUMEN
The mechanism of the binding of D,L dansyl amino acids to teicoplanin was investigated. Na+ was used as an indicator of the interactions between the solutes and teicoplanin. The number (n) of sodium ions, Na+, excluded from the solute-teicoplanin interface when analyte transfer occurred was determined. A thermodynamic study and enthalpy-entropy compensation were performed to further explore the interaction mechanism. From these results, it was shown that teicoplanin was balanced between 2 conformational states characterized by distinct enantioselective properties. This approach indicates that liquid chromatography (LC) is a useful tool to extract physicochemical and molecular information from retention data. Thus, LC can be used as a complementary technique with the conventional techniques of molecular interaction analysis.
Asunto(s)
Aminoácidos/química , Antibacterianos/química , Compuestos de Dansilo/química , Sodio/química , Teicoplanina/química , Algoritmos , Cromatografía Liquida , Indicadores y Reactivos , Estereoisomerismo , TermodinámicaRESUMEN
The chiral recognition mechanism for a series of d,l phenoxypropionic acid herbicides (PPAs) on a teicoplanin stationary phase was investigated in reversed phase liquid chromatography (RPLC) over a wide range of mobile phase pH and column temperature. The effect of methanol on the enantiomeric separation was studied by varying its fraction (v/v) in the mobile phase. The thermodynamic data indicated that the chiral recognition was controlled by the interaction between the anionic form of the solute and the teicoplanin phase while those with the neutral form played a minor role. In addition, it was demonstrated that the enhancement of the separation factor observed as the methanol fraction increased in the mobile phase was enthalpically controlled owing to stereoselective binding interactions. Such behavior was used to optimize the chromatographic conditions for separation of PPAs herbicides on teicoplanin.