Biomedical subjects

Ines Slama

Publications and source records attributed to Ines Slama.

4 recordsLinked to original sources

PubMed2003

Role of the vancomycin-ristocetin heterodimerization on the enantioselectivity of D,L-tryptophan and D,L-dansyl tryptophan.

In this paper, a chromatographic system using immobilized ristocetin as chiral stationary phase and vancomycin as chiral mobile phase additive (CMPA) was described in order to investigate the role of the glycopeptide heterodimerization on the retention and enantioselectivity of D,L-tryptophan and D,L-dansyl tryptophan. A simplified interaction model was derived considering the formation of heterodimers between immobilized ristocetin and vancomycin. This theoretical approach was convenient to describe adequately the retention behavior. When the CMPA concentration increased, the solute retention factor increased for all the solute enantiomers studied indicating that the vancomycin adsorbed on the immobilized ristocetin played a preponderant role in the retention. The D,L-tryptophan enantioselectivity on the dynamically modified stationary phase was improved by a factor of 1.3, probably due to a glycopeptide conformational change upon heterodimerization. On the other hand, a decrease in the chiral discrimination of D,L-dansyl tryptophan was observed. Such a behavior seems to result from the antagonist enantioselective properties of the two glycopeptides for the dansyl amino acids.

Chromatography, High Pressure Liquid↗

PubMed2002

Vancomycin dimerization and chiral recognition studied by high-performance liquid chromatography.

The retention and separation of D,L-dansylvaline enantiomers (used as test solutes) were investigated using silica gel as stationary phase and vancomycin as chiral mobile-phase additive. A retention model was developed to describe the mechanistic aspects of the interaction between solute and vancomycin in the chromatographic system. It considered the formation of vancomycin dimers both "free" in the mobile phase and adsorbed on silica. By fitting the model equation to experimental data, it appeared clearly that the approach taking into account the vancomycin dimerization described accurately the retention behavior of the compounds. The examination of the model equation parameters showed that the glycopeptide dimerization increased the enantioselectivity by a factor of approximately 3.7. This study demonstrated the preponderant role of the vancomycin dimerization on the chiral recognition process of D,L-dansylvaline. Also, an additional analysis on a vancomycin chiral stationary phase indicated that the addition of vancomycin in the mobile phase promoted a greater enantioselectivity mediated by the formation of dimers in the stationary phase.

Algorithms↗

PubMed2002

A framework based on the extended Wyman concept for analyzing the salt effects on the solute retention in high-performance affinity chromatography.

The analysis of binding data of a ligand to a macromolecule in the presence of an additive can be classically formulated in terms of the linked functions of Wyman. In the case of a salt, this approach has been extended by Tanford such that the contributions of both salt and water are taken into account. In this paper, the extended Wyman theory was applied to high-performance affinity chromatography (HPAC) in order to define a general model describing the effects of the mobile-phase salts on the ligand binding. Various HPAC literature data, as well as our data concerning dansyl amino acid retention on a vancomycin stationary phase, were examined in relation to this model. From the results, this theoretical approach was considered to be adequate to describe accurately the salt dependence on solute retention. This work shows the importance of taking into account the effects of both ionic species and water in the investigation of relative contributions of the interactions involved in the ligand binding to immobilized receptor.

Journal Article↗

PubMed2002

Displacement study on a vancomycin-based stationary phase using N-acetyl-D-alanine as a competing agent.

The analysis of the binding data of D,L-dansyl amino acids on a vancomycin stationary phase is investigated in relation to the addition of N-acetyl-D-alanine in the mobile phase. This eluent additive acts as a specific competing agent for the aglycone pocket of the immobilized chiral selector. A model taking into account both stereoselective and nonstereoselective interactions between the solutes and the stationary phase is used to fit the experimental data. From the results, the theoretical approach is considered to be adequate to describe the competing agent dependence on solute retention. To the best of our knowledge, this report constitutes the first example of a displacement study on a macrocyclic antibiotic stationary phase. This work shows that dansyl amino acids bind to the active aglycone pocket of the selector and that this interaction is enantioselective. The results also demonstrate that additional enantioselective sites at the vancomycin surface are involved in the chiral discrimination of these solutes.

Alanine↗