Study of tryptophan enantiomer binding to a teicoplanin-based stationary phase using the perturbation technique. Investigation of the role of sodium perchlorate in solute retention and enantioselectivity.
The retention of D,L-tryptophan enantiomers on an immobilized teicoplanin column was investigated in relation to the mobile phase sodium perchlorate concentration using the perturbation method to determine the solute distribution isotherms. From the experimental data, it appeared that the bi-Langmuir model was able to describe D- and L-enantiomer retention on the immobilized selector over the salt concentration range. An increase in the apparent enantioselectivity with an increase in sodium perchlorate concentration was observed. The chiral recognition enhancement was governed by (i) an increase in the difference of the adsorption constants for binding to the high-affinity site (aglycone pocket) between the two enantiomers and (ii) enhancement of the number of aglycone chiral regions interacting with D-tryptophan. It is suggested that an ion-pair formation mechanism between perchlorate and solute and/or selector is responsible for this behavior. In addition, this work shows that additional secondary sites on the teicoplanin surface are involved in the apparent enantioselectivity at low sodium perchlorate concentrations.
Loukili
Bouchra
B
Equipe de Chimie Analytique, Département de Pharmacochimie Moléculaire, UMR 5063 CNRS-UJF, UFR de Pharmacie de Grenoble, Domaine de la Merci, 38700 La Tronche, France.
Dufresne
Christelle
C
Jourdan
Eric
E
Grosset
Catherine
C
Ravel
Anne
A
Villet
Annick
A
Peyrin
Eric
E
D010472:Perchlorates / Q000737:chemistry*; D017670:Sodium Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D014364:Tryptophan / Q000737:chemistry / Q000378:metabolism*
D010472:Perchlorates; D017670:Sodium Compounds; D014364:Tryptophan; C031068:sodium perchlorate