Biomedical subjects

Eric Peyrin

Publications and source records attributed to Eric Peyrin.

17 recordsLinked to original sources

PubMed2006

Chiral resolution of histidine using an anti-D-histidine L-RNA aptamer microbore column.

In this paper, we report a new anti-amino acid aptamer chiral stationary phase (CSP). The enantiomers of histidine were separated using an immobilized histidine-specific L-RNA aptamer (40-mer) and an aqueous buffer as mobile phase. The effects of the variation of different operating parameters, including the mobile phase pH and the MgCl2 concentration as well as the column temperature, on the solute retention were assessed. The results suggested that (i) the protonated form of histidine was involved in the stereospecific RNA binding and (ii) Mg2+ was essential for the target enantiomer binding to the specific aptamer sites. From a practical point of view, it appeared that the baseline resolution in a minimum analysis time can be achieved at a column temperature of 35 degrees C for an eluent containing 10 mM of MgCl2, pH 5.5.

Aptamers, Nucleotide↗

PubMed2006

Enantiomeric separation using an l-RNA aptamer as chiral additive in partial-filling capillary electrophoresis.

In this paper, we report the chiral resolution of arginine using an anti-arginine l-RNA aptamer chiral selector in partial-filling CE. The effects of the capillary temperature, sample load, and aptamer plug length on the enantiomeric separation were assessed. Very high chiral resolving capability was observed at low or moderate capillary temperatures (the target peak being not detected in the separation window), whereas the practical chiral resolution was achieved only at high enough temperatures (50-60 degrees C). Over this high-temperature range, the electrophoretic behavior of the target enantiomer appeared to result from a combination of binding site heterogeneity, slow desorption kinetics, and concentration overload of aptamer binding sites. From additional thermal UV melting experiments, three RNA conformations were identified for the 50-60 degrees C temperatures. It was suggested that the presence of these different RNA conformations was a plausible source of the binding site heterogeneity.

Aptamers, Nucleotide↗

PubMed2006

Liquid chromatography, electrochromatography and capillary electrophoresis applications of DNA and RNA aptamers.

The development of the systematic evolution of ligands by exponential enrichment (SELEX) process has allowed the isolation of oligonucleotide sequences (referred as aptamers) with the capacity to recognize various classes of target molecules with high affinity and specificity. At the present time, various analytical aptamer-based formats have been developed as suitable tools for the detection and quantification of numerous targets, possessing many potential advantages over the most popular antibody technology. In this review, the aptamer applicability to the separation, purification and quantification of various analytes by liquid chromatography, capillary electrophoresis and electrochromatography is addressed.

Chromatography, Liquid↗

PubMed2006

Recent developments in the HPLC enantiomeric separation using chiral selectors identified by a combinatorial strategy.

Two kinds of chiral stationary phases (CSPs) can be distinguished: (i) the "conventional" CSPs for which the selectivity is not pre-determined and (ii) the CSPs which are characterized by a predictable elution order, depending on the target enantiomer used for the selection of the chiral selector. At the present time, three general methodologies have been described to create chiral selectors specifically designed against the racemate to resolve: the molecular imprinting technology, the production of antibodies and the combinatorial approach. The latter methodology involves two categories of procedures to develop CSPs: an approach from a small library of low-molecular weight selectors and an approach from a very large library of single-stranded oligonucleotides (DNA and RNA aptamers). In this review, the recent advances in the HPLC applications of the chiral selectors identified through these two combinatorial procedures are addressed.

Amino Acids↗

PubMed2005

A L-RNA aptamer chiral stationary phase for the resolution of target and related compounds.

In this paper, we report for the first time an aptamer-based chiral stationary phase (CSP) able to resolve racemates of both target and various related compounds. The enantiomers of tyrosine and analogues (11 enantiomeric pairs) were separated using an immobilized tyrosine-specific L-RNA aptamer as CSP and an aqueous buffer (8 mM Tris-HCl buffer, 25 mM NaCl, 5 mM MgCl2; pH 7.4) as mobile phase, at a column temperature of 10 degrees C. It appeared that the carboxylic and amino groups as well as the aromatic side chain of amino acid controlled the stereospecific recognition. Modifications on the polar groups were strongly detrimental for enantioselectivity while the replacement of the phenolic group by some bicyclic aromatic residues of different polarity, size or shape did not impair the enantioselective interaction. In addition, the effects of the mobile phase composition and column temperature upon the retention and stereoselective properties of the CSP were assessed. Finally, it was found that the immobilized RNA aptamer could be used under hydro-organic mobile phase conditions without alteration of the stationary phase stability.

Base Sequence↗

PubMed2005

Chiral stationary phase based on a biostable L-RNA aptamer.

An immobilized anti-L-arginine d-RNA aptamer, used as a target-specific chiral stationary phase (CSP), was found to be very quickly degraded by RNases under usual chromatographic utilization and storage. To overcome this severe limitation for a practical use, a CSP based on the L-RNA aptamer, that is, the mirror image of the D-RNA aptamer, was created. It was shown that this mirror-image approach was a very simple and powerful strategy to develop a highly stable stationary phase due to the intrinsic insensitivity of l-RNA to the RNase degradation. In addition, such an approach allowed one to reverse the enantiomer elution order relative to that obtained with the corresponding d-RNA CSP.

Aptamers, Nucleotide↗

PubMed2005

Thermodynamic origin of the chiral recognition of tryptophan on teicoplanin and teicoplanin aglycone stationary phases.

The D-, L-tryptophan binding and the chiral recognition properties of the teicoplanin and teicoplanin aglycone (TAG) chiral stationary phase (CSPs) were compared at various column temperatures. The solute adsorption isotherms (bi-Langmuir model) were determined for both the two CSPs using the perturbation method. It was demonstrated that the sugar units were involved in the reduction of the apparent enantioselectivity through two phenomena: (i) the inhibition of some enantioselective contacts with low-affinity binding regions of the aglycone and (ii) a decrease in the stereoselective properties of the aglycone high-affinity binding pocket. The phenomenon (ii) was governed by both a decrease in the ratio of the enantiomer adsorption constant and a strong reduction of the site accessibility for D- and L-tryptophan. In addition, a temperature effect study was performed to investigate the chiral recognition mechanism at the aglycone high-affinity pocket. An enthalpy-entropy compensation analysis derived from the Grunwald model as well as the comparison with the literature data demonstrated that the enantioselective binding mode was dependent on an interface dehydration process. The change in the enantioselective process observed between the TAG and teicoplanin CSP was characterized by a difference of ca. 2-3 ordered water molecules released from the species interface.

Absorption↗

PubMed2004

Streptavidin chiral stationary phase for the separation of adenosine enantiomers.

In this paper, a microbore column packed with streptavidin particles was used, at various temperatures (0-24 degrees C), to separate the adenosine enantiomers by HPLC. Using an aqueous mobile phase, the apparent enantioseparation was high for a small molecule, varying from 11.5 at 0 degrees C to 6.2 at 24 degrees C. From the experiments carried out with a streptavidin-biotin complex stationary phase, it was demonstrated that the blockage of the biotin sites of the immobilized streptavidin was responsible for a strong decrease in the enantioselectivity via a direct and/or an indirect effect. From the analysis of the concentration dependencies of the solute retention factor, it was also shown that a reduction of the D-adenosine specific binding sites occurred at the lowest temperature. The thermodynamic parameters determined from the van't Hoff plots indicated that the D-adenosine binding to the streptavidin specific sites was enthalpically driven.

Adenosine↗

PubMed2004

Immobilized DNA aptamers as target-specific chiral stationary phases for resolution of nucleoside and amino acid derivative enantiomers.

Recently, we described the use of a DNA aptamer as a new target-specific chiral stationary phase (CSP) for the separation of oligopeptide enantiomers (Michaud, M.; Jourdan, E.; Villet, A.; Ravel, A.; Grosset, C.; Peyrin, E. J. Am. Chem. Soc. 2003, 125, 8672). However, from a practical point of view, it was fundamental to extend the applicability of such target-specific aptamer CSP to the resolution of small (bioactive) molecule enantiomers. In this paper, immobilized DNA aptamers specifically selected against D-adenosine and L-tyrosinamide were used to resolve the enantiomers by HPLC, using microbore columns. At 20 degrees C, the adenosine enantioseparation was similar to that classically reported with imprinted CSPs (approximately 3.5) while a very high enantioselectivity was observed for the tyrosinamide enantiomers (the nontarget enantiomer was essentially nonretained on the CSP). The influence of temperature on solute binding and chiral discrimination was analyzed. The binding enthalpic contributions were determined from linear van't Hoff plots. Very large DeltaH values were obtained for the target enantiomers (-71.4 +/- 0.7 kJ/mol for D-adenosine and -139.4 +/- 2.0 kJ/mol for L-tyrosinamide). Such values were consistent with the formation of a tight complex between these analytes and the aptamer CSPs. This work demonstrates that target-specific aptamer CSPs constitute a powerful tool for the resolution of small (bioactive) molecule enantiomers.

Adenosine↗

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↗

PubMed2003

A DNA aptamer as a new target-specific chiral selector for HPLC.

In this paper, a DNA aptamer, known to bind stereospecifically the D-enantiomer of an oligopeptide, i.e., arginine-vasopressin, was immobilized on a chromatographic support. The influence of various parameters (such as column temperature, eluent pH, and salt concentration) on the L- and D-peptide retention was investigated in order to provide information about the binding mechanism and then to define the utilization conditions of the aptamer column. The results suggest that dehydration at the binding interface, charge-charge interactions, and adaptive conformational transitions contribute to the specific D-peptide-aptamer complex formation. A very significant enantioselectivity was obtained in the optimal binding conditions, the D-peptide being strongly retained by the column while the L-peptide eluted in the void volume. A rapid baseline separation of peptide enantiomers was also achieved by modulating the elution conditions. Furthermore, it was established that the aptamer column was stable during an extended period of time. This work indicates that DNA aptamers, specifically selected against an enantiomer, could soon become very attractive as new target-specific chiral selectors for HPLC.

Arginine Vasopressin↗

PubMed2003

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.

Perchlorates↗

PubMed2002

Salt effects on the interaction of an amphiphilic model molecule with immobilized phosphatidylcholine monolayers.

The retention of hydrocortisone (used as an amphiphilic model solute) on an immobilized artificial membrane (IAM) column was investigated in relation to the mobile phase concentration of three sodium salts (representing different rankings in the Hofmeister series, i.e. perchlorate, chloride and sulfate) in order to provide insight into the nature of the solute interactions with phospholipid monolayers. The influence of the salt series on solute retention was found to follow the Hofmeister series, emphasizing the role of hydrophobic effect in the solute retention mechanism on phospholipid monolayers. Retention models based on the extended Wyman relations (preferential interaction theory) were developed to analyze more quantitatively the salt effects on the hydrocortisone retention factor. This analysis as well as additional thermodynamic study suggested that the hydrocortisone binding to IAM involved both an insertion into the hydrophobic inside governed by hydrophobic effects and contacts with the interfacial region implying interactions such as van der Waals interactions/hydrogen bonds between the solute hydroxyl groups and the polar headgroups of phospholipidmonolayers.

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

Chromatographic determination of the association constants between nimesulide and native and modified beta-cyclodextrins.

The retention of a non-steroidal anti-inflammatory drug (NSAID), i.e. nimesulide, in high performance liquid chromatography (HPLC) was investigated using a phenyl bond silica column and beta-cyclodextrin (beta-CD) or hydroxypropyl-beta-cyclodextrin (HP-beta-CD) as mobile phase additive (0-10 mM). Such a study was carried out in order to determine the most efficient cyclodextrin as a potential drug complexing agent for a future application in pharmaceutical formulation. Assuming a 1:1 stoichiometry, the association constants (K) were calculated from the chromatographic data. At a column temperature of 25 degrees C and in a highly aqueous medium (98% phosphate buffer-2% methanol (v/v)), K was equal to 523 and 1285 M(-1) for the nimesulide-beta-CD and nimesulide HP-beta-CD complexes, respectively. These results were consistent with the data reported previously using phase solubility studies and UV spectrophotometry. As well, the thermodynamic parameters of the inclusion complexes were determined from linear van't Hoff plots for the two inclusion complexes. From the enthalpy and entropy changes, it appeared that nimesulide interact more strongly with HP-beta-CD due to a significant hydrophobic effect between the compound and the flexible hydroxypropyl groups.

2-Hydroxypropyl-beta-cyclodextrin↗

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↗