This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino a...This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine (und-Leu) as the chiral pseudostationary phase in capillary electrophoresis. The effects of using two different counterions (sodium and lysine) on the chiral recognition of binaphthyl derivatives were compared at varying pH conditions. The enantiomeric separation of BNA and BNP enantiomers via capillary electrophoresis, using und-Leu as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium as the counterion. More specifically, at a surfactant concentration of 45 mM, at pH 7, a significant increase in chiral selectivity was observed when lysine was used as the counterion compared to sodium. The enantiomeric resolution of BNA and BNP increased by 6-fold and 1.1-fold, respectively, in capillary electrophoresis experiments when lysine was utilized as the counterion compared to using sodium. Furthermore, the retention factor of BNA and BNP enantiomers also increased approximately 3.5-fold and 4-fold, respectively, in the presence of lysine counterions as compared to using sodium counterions. When running buffer in capillary electrophoresis was increased to pH 11, the resolution and retention factors were nearly identical when comparing the effects of the sodium and lysine counterions. This signifies the important role of lysine’s positive net charge on chiral recognition. This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis.展开更多
The separation of enantiomers is of great importance in biology, pharmaceutics, agriculture and environment. The different separation modes (i.e. capillary zone electrophoresis (CZE), micellar electrokinetic chromatog...The separation of enantiomers is of great importance in biology, pharmaceutics, agriculture and environment. The different separation modes (i.e. capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC), capillary electrochromatography (CEC), etc) and many chiral selectors available make capillary electrophoresis (CE) technique a powerful tool for chiral analysis[1]. On the basis of ligand-exchange (LE) mechanism introduced by Davankov and Rogozhin[2] in the early 1970s for high performance liquid chromatography (HPLC), the first application of CE in chiral separation was reported by Zare's group[3,4]. Using Cu(Ⅱ) complexes of L-histidine or aspartame as chiral selectors, 14 dansyl amino acids (Dns-AAs) were resolved. The authors observed a significant improvement in resolution when a micelle forming surfactant such as sodium dodecyl sulfate (SDS) was added to the electrolyte performing MEKC. The method was called as ligand-exchange micellar electrokinetic capillary chromatography (LE-MEKC). As a hybrid mode of possessing both the advantage of high enantioselectivity in ligand-exchange mechanism and the main advantages of MEKC, LE-MEKC allows the manipulation of the selectivity for large classes of neutral and charged compounds, making possible separation that otherwise are not feasible by using only the mode of LE or MEKC. Using this combined separation mode, hydroxy acids and dipeptides, as well as 16 positional and optical isomers of tryptophan derivatives could be optically resolved[5]. The same group also proposed a method for the determination of the critical micelle concentration (CMC) of anionic surfactants based on LE-MEKC principle[6].展开更多
Reverse micelles create unique environment in organic media. They are capable of solubilizing hydrophilic biomolecules （e.g., proteins, peptides, amino acids, and DNAs） in their aqueous interior. This feature brings...Reverse micelles create unique environment in organic media. They are capable of solubilizing hydrophilic biomolecules （e.g., proteins, peptides, amino acids, and DNAs） in their aqueous interior. This feature brings about the practical use of biomaterials in organic media because reverse micelles solubilize them with the intrinsic activity. In this paper, we focus on recent two topics concerning protein extraction and chiral separation of biomolecules using liquid membranes. In the first topic, we present recent attempts to extract proteins from an aqueous solution into isooctane using reverse micelles, and some important operational parameters to achieve an efficient protein transfer are discussed. Furthermore, novel function of reverse micelles as a protein activation medium is introduced. In the reverse micellar phase, denatured proteins were completely reactivated in the reverse micellar solution. The reverse micellar technique is found to be a useful tool not only for protein separation but also for protein refolding. Furthermore, we found that a cyclic ligand carixarene has an extraction ability to set up optimum conditions for protein transfer. In the second topic, we have found that a supported liquid membrane （SLM） encapsulating enzymes shows high enantioselectivity （enantioselective excess value is over 96%） in the transport of racemic pharmaceutical compound ibuprofen. A different experiment also suggests that the α-chymotrypsin-catalyzed reactions droved the enantioselective transport of L-phenylalanine based on the enantioselectivity of the enzyme. The SLM encapsulating the surfactant-enzyme complex enabled the highly enantioselective separation of racemic mixtures. It can be envisioned that arrangement of appropriate enzymes in the SLM system will allow enantioselective separation of various useful organic compounds.展开更多
文摘This study investigates the effect of counterions on the chiral recognition of 1,1'-Binaphthyl-2,2'-diamine (BNA) and 1,1'-Binaphthyl-2,2'-diyl hydrogenphosphate (BNP) enantiomers when using an amino acid-based surfactant undecanoyl L-leucine (und-Leu) as the chiral pseudostationary phase in capillary electrophoresis. The effects of using two different counterions (sodium and lysine) on the chiral recognition of binaphthyl derivatives were compared at varying pH conditions. The enantiomeric separation of BNA and BNP enantiomers via capillary electrophoresis, using und-Leu as the chiral recognition medium, significantly improved the enantiomeric resolution in capillary electrophoresis at pH 7 when using Lysine counterions as compared to using sodium as the counterion. More specifically, at a surfactant concentration of 45 mM, at pH 7, a significant increase in chiral selectivity was observed when lysine was used as the counterion compared to sodium. The enantiomeric resolution of BNA and BNP increased by 6-fold and 1.1-fold, respectively, in capillary electrophoresis experiments when lysine was utilized as the counterion compared to using sodium. Furthermore, the retention factor of BNA and BNP enantiomers also increased approximately 3.5-fold and 4-fold, respectively, in the presence of lysine counterions as compared to using sodium counterions. When running buffer in capillary electrophoresis was increased to pH 11, the resolution and retention factors were nearly identical when comparing the effects of the sodium and lysine counterions. This signifies the important role of lysine’s positive net charge on chiral recognition. This study provides insight into the potential advantages of using cationic, pH-dependent counterions such as lysine to significantly improve the chiral recognition of binaphthyl derivatives when using chiral anionic surfactants as the pseudostationary phase in capillary electrophoresis.
文摘The separation of enantiomers is of great importance in biology, pharmaceutics, agriculture and environment. The different separation modes (i.e. capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC), capillary electrochromatography (CEC), etc) and many chiral selectors available make capillary electrophoresis (CE) technique a powerful tool for chiral analysis[1]. On the basis of ligand-exchange (LE) mechanism introduced by Davankov and Rogozhin[2] in the early 1970s for high performance liquid chromatography (HPLC), the first application of CE in chiral separation was reported by Zare's group[3,4]. Using Cu(Ⅱ) complexes of L-histidine or aspartame as chiral selectors, 14 dansyl amino acids (Dns-AAs) were resolved. The authors observed a significant improvement in resolution when a micelle forming surfactant such as sodium dodecyl sulfate (SDS) was added to the electrolyte performing MEKC. The method was called as ligand-exchange micellar electrokinetic capillary chromatography (LE-MEKC). As a hybrid mode of possessing both the advantage of high enantioselectivity in ligand-exchange mechanism and the main advantages of MEKC, LE-MEKC allows the manipulation of the selectivity for large classes of neutral and charged compounds, making possible separation that otherwise are not feasible by using only the mode of LE or MEKC. Using this combined separation mode, hydroxy acids and dipeptides, as well as 16 positional and optical isomers of tryptophan derivatives could be optically resolved[5]. The same group also proposed a method for the determination of the critical micelle concentration (CMC) of anionic surfactants based on LE-MEKC principle[6].
基金Supported by a Grant-in-Aid for Scientific Research (No. 17656271) from the Ministry of Education, Science, Sports, and Culture of Japan.
文摘Reverse micelles create unique environment in organic media. They are capable of solubilizing hydrophilic biomolecules （e.g., proteins, peptides, amino acids, and DNAs） in their aqueous interior. This feature brings about the practical use of biomaterials in organic media because reverse micelles solubilize them with the intrinsic activity. In this paper, we focus on recent two topics concerning protein extraction and chiral separation of biomolecules using liquid membranes. In the first topic, we present recent attempts to extract proteins from an aqueous solution into isooctane using reverse micelles, and some important operational parameters to achieve an efficient protein transfer are discussed. Furthermore, novel function of reverse micelles as a protein activation medium is introduced. In the reverse micellar phase, denatured proteins were completely reactivated in the reverse micellar solution. The reverse micellar technique is found to be a useful tool not only for protein separation but also for protein refolding. Furthermore, we found that a cyclic ligand carixarene has an extraction ability to set up optimum conditions for protein transfer. In the second topic, we have found that a supported liquid membrane （SLM） encapsulating enzymes shows high enantioselectivity （enantioselective excess value is over 96%） in the transport of racemic pharmaceutical compound ibuprofen. A different experiment also suggests that the α-chymotrypsin-catalyzed reactions droved the enantioselective transport of L-phenylalanine based on the enantioselectivity of the enzyme. The SLM encapsulating the surfactant-enzyme complex enabled the highly enantioselective separation of racemic mixtures. It can be envisioned that arrangement of appropriate enzymes in the SLM system will allow enantioselective separation of various useful organic compounds.
