The Experts below are selected from a list of 72 Experts worldwide ranked by ideXlab platform
Kazuaki Kakehi - One of the best experts on this subject based on the ideXlab platform.
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Capillary-based lectin Affinity Electrophoresis for interaction analysis between lectins and glycans.
Methods in molecular biology (Clifton N.J.), 2014Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:Capillary Affinity Electrophoresis (CAE) is a powerful technique for glycan analysis, and one of the analytical approaches for analyzing the interaction between lectins and glycans. The method is based on the high-resolution separation of fluorescently labeled glycans by Capillary Electrophoresis (CE) with laser-induced fluorescence detection (LIF) in the presence of lectins (or glycan binding proteins). CAE allows simultaneous determination of glycan structures in a complex mixture of glycans. In addition, we can calculate the binding kinetics on a specific glycan in the complex mixture of glycans with a lectin. Here, we show detailed procedures for Capillary Affinity Electrophoresis of fluorescently labeled glycans with lectins using CE-LIF apparatus. Its application to screening a sialic acid binding protein in plant barks is also shown.
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Advanced techniques for carbohydrate analysis by Capillary Electrophoresis.
SEIBUTSU BUTSURI KAGAKU, 2008Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:Carbohydrate analysis absolutely depends on high-resolution separation, because oligosaccharides derived from glycoconjugates are usually composed of an extremely complex mixture of carbohydrates including isomers. Capillary Electrophoresis (CE) is one of the most powerful techniques in terms of resolving power, and a combination of CE and laser-induced fluorescence (LIF) detection enables to detect carbohydrates at fmol (10−15 mol) to amol (10−18 mol). CE is currently applied to the analysis of various carbohydrates derived from glycoconjugates. This review describes the recent development in high sensitive analysis of carbohydrates using LIF-CE, and the techniques for profiling of carbohydrates using Capillary Affinity Electrophoresis (CAE).
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Capillary Affinity Electrophoresis using lectins for the analysis of milk oligosaccharide structure and its application to bovine colostrum oligosaccharides.
Analytical biochemistry, 2005Co-Authors: Kazuki Nakajima, Mitsuhiro Kinoshita, Namiko Matsushita, Tadasu Urashima, Minoru Suzuki, Akemi Suzuki, Kazuaki KakehiAbstract:Abstract Animal colostrum and milk contain complex mixtures of oligosaccharides, which have species-specific profiles. Milk oligosaccharides have various types of structure related to the core structures of glycolipids and N - and O -glycans of glycoproteins and provide a good library to examine the binding of oligosaccharides to various lectins. Recently, we reported a Capillary Affinity Electrophoresis (CAE) method for analyzing the interactions between lectins and complex mixtures of N -linked oligosaccharides prepared from serum glycoproteins [K. Nakajima, Y. Oda, M. Kinoshita, K. Kakehi, J. Proteome Res. 2 (2003) 81–88]. The present paper reports the interactions between 24 milk oligosaccharides and six lectins (PA-I, RCA 120 , SBA, WGA, UEA-I, and AAL) analyzed using CAE. Based on the resulting data, we constructed a library that enables us to determine nonreducing terminal monosaccharides, such as Gal, GalNAc, GlcNAc, and Fuc, and to differentiate Gal- or Fuc-linked isomers, such as lacto- N -tetraose, lacto- N -neotetraose, and lacto- N -fucopentaose II and III. In addition, using the library, we show that a combination of the lectins can characterize the neutral oligosaccharides derived from bovine colostrum.
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Synthesis and molecular recognition of carbohydrate-centered multivalent glycoclusters by a plant lectin RCA120.
Bioorganic & Medicinal Chemistry, 2005Co-Authors: Atsuko Eguchi, Kazuaki KakehiAbstract:Water soluble and lectin-recognizable carbohydrate-centered glycoclusters were prepared efficiently by the Huisgen 1,3-cycloaddition reaction of methyl-2,3,4,6-tetra-O-propargyl β-d-galactopyranoside with 2-azidoethyl glycosides of lactose and N-acetyllactosamine. Their binding by a plant lectin RCA120 was examined by Capillary Affinity Electrophoresis using fluorescence-labeled asialoglycans from human α1-acid glycoprotein. The glycoclusters showed 400-fold stronger inhibitory effect than free lactose, manifesting strong multivalency effect.
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Analysis of the interaction between hyaluronan and hyaluronan-binding proteins by Capillary Affinity Electrophoresis: significance of hyaluronan molecular size on binding reaction.
Journal of Chromatography B, 2004Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:We developed a method for the analysis of the interaction between hyaluronan (HA) oligosaccharides and hyaluronan-binding proteins (HABPs) using Capillary Affinity Electrophoresis (CAE). The method is based on high-resolution separation of fluorescent-labeled HA molecules in the presence of hyaluronan-binding proteins at different concentrations by Capillary Electrophoresis (CE) with laser-induced fluorescent detection. Hyaluronan-binding protein from bovine nasal cartilage interacts strongly with HA decasaccharide or larger oligosaccharides. Effect of the molecular size of HA oligomers clearly showed that longer carbohydrate chains than decasaccharide were required for recognition by HA binging protein. Interestingly, the interaction did not cause retardation of HA oligomers as observed in many binding reactions such as the interaction between pharmaceuticals and serum albumin, but showed disappearance of the oligomer peak. Although we cannot explain the accurate mechanism on the interaction, disappearance is probably due to low equilibrium rate between free and conjugate states. The present technique will be useful to compare the relative binding Affinity, and to understand the mechanism on the interaction between hyaluronan and hyaluronan-binding proteins.
Mitsuhiro Kinoshita - One of the best experts on this subject based on the ideXlab platform.
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Capillary-based lectin Affinity Electrophoresis for interaction analysis between lectins and glycans.
Methods in molecular biology (Clifton N.J.), 2014Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:Capillary Affinity Electrophoresis (CAE) is a powerful technique for glycan analysis, and one of the analytical approaches for analyzing the interaction between lectins and glycans. The method is based on the high-resolution separation of fluorescently labeled glycans by Capillary Electrophoresis (CE) with laser-induced fluorescence detection (LIF) in the presence of lectins (or glycan binding proteins). CAE allows simultaneous determination of glycan structures in a complex mixture of glycans. In addition, we can calculate the binding kinetics on a specific glycan in the complex mixture of glycans with a lectin. Here, we show detailed procedures for Capillary Affinity Electrophoresis of fluorescently labeled glycans with lectins using CE-LIF apparatus. Its application to screening a sialic acid binding protein in plant barks is also shown.
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Advanced techniques for carbohydrate analysis by Capillary Electrophoresis.
SEIBUTSU BUTSURI KAGAKU, 2008Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:Carbohydrate analysis absolutely depends on high-resolution separation, because oligosaccharides derived from glycoconjugates are usually composed of an extremely complex mixture of carbohydrates including isomers. Capillary Electrophoresis (CE) is one of the most powerful techniques in terms of resolving power, and a combination of CE and laser-induced fluorescence (LIF) detection enables to detect carbohydrates at fmol (10−15 mol) to amol (10−18 mol). CE is currently applied to the analysis of various carbohydrates derived from glycoconjugates. This review describes the recent development in high sensitive analysis of carbohydrates using LIF-CE, and the techniques for profiling of carbohydrates using Capillary Affinity Electrophoresis (CAE).
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Capillary Affinity Electrophoresis using lectins for the analysis of milk oligosaccharide structure and its application to bovine colostrum oligosaccharides.
Analytical biochemistry, 2005Co-Authors: Kazuki Nakajima, Mitsuhiro Kinoshita, Namiko Matsushita, Tadasu Urashima, Minoru Suzuki, Akemi Suzuki, Kazuaki KakehiAbstract:Abstract Animal colostrum and milk contain complex mixtures of oligosaccharides, which have species-specific profiles. Milk oligosaccharides have various types of structure related to the core structures of glycolipids and N - and O -glycans of glycoproteins and provide a good library to examine the binding of oligosaccharides to various lectins. Recently, we reported a Capillary Affinity Electrophoresis (CAE) method for analyzing the interactions between lectins and complex mixtures of N -linked oligosaccharides prepared from serum glycoproteins [K. Nakajima, Y. Oda, M. Kinoshita, K. Kakehi, J. Proteome Res. 2 (2003) 81–88]. The present paper reports the interactions between 24 milk oligosaccharides and six lectins (PA-I, RCA 120 , SBA, WGA, UEA-I, and AAL) analyzed using CAE. Based on the resulting data, we constructed a library that enables us to determine nonreducing terminal monosaccharides, such as Gal, GalNAc, GlcNAc, and Fuc, and to differentiate Gal- or Fuc-linked isomers, such as lacto- N -tetraose, lacto- N -neotetraose, and lacto- N -fucopentaose II and III. In addition, using the library, we show that a combination of the lectins can characterize the neutral oligosaccharides derived from bovine colostrum.
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Analysis of the interaction between hyaluronan and hyaluronan-binding proteins by Capillary Affinity Electrophoresis: significance of hyaluronan molecular size on binding reaction.
Journal of Chromatography B, 2004Co-Authors: Mitsuhiro Kinoshita, Kazuaki KakehiAbstract:We developed a method for the analysis of the interaction between hyaluronan (HA) oligosaccharides and hyaluronan-binding proteins (HABPs) using Capillary Affinity Electrophoresis (CAE). The method is based on high-resolution separation of fluorescent-labeled HA molecules in the presence of hyaluronan-binding proteins at different concentrations by Capillary Electrophoresis (CE) with laser-induced fluorescent detection. Hyaluronan-binding protein from bovine nasal cartilage interacts strongly with HA decasaccharide or larger oligosaccharides. Effect of the molecular size of HA oligomers clearly showed that longer carbohydrate chains than decasaccharide were required for recognition by HA binging protein. Interestingly, the interaction did not cause retardation of HA oligomers as observed in many binding reactions such as the interaction between pharmaceuticals and serum albumin, but showed disappearance of the oligomer peak. Although we cannot explain the accurate mechanism on the interaction, disappearance is probably due to low equilibrium rate between free and conjugate states. The present technique will be useful to compare the relative binding Affinity, and to understand the mechanism on the interaction between hyaluronan and hyaluronan-binding proteins.
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screening method of carbohydrate binding proteins in biological sources by Capillary Affinity Electrophoresis and its application to determination of tulipa gesneriana agglutinin in tulip bulbs
Glycobiology, 2004Co-Authors: Kazuki Nakajima, Yasuo Oda, Mitsuhiro Kinoshita, Takashi Masuko, Hanae Kaku, Naoto Shibuya, Kazuaki KakehiAbstract:We developed Capillary Affinity Electrophoresis (CAE) to analyze the molecular interaction between carbohydrate chains and proteins in solution state. A mixture of oligosaccharides derived from a glycoprotein was labeled with 8-aminopyrene-1,3,6-trisulfonate (APTS), and used as glycan library without isolation. Interaction of a carbohydrate-binding protein with each oligosaccharide in the mixture could be simultaneously observed, and relative affinities of oligosaccharides toward the protein were accurately determined. In this study, we applied CAE to detect the presence of lectins in some plants (Japanese elderberry bark and tulip bulb). In the crude extract of the elderberry bark, binding activity toward sialo-carbohydrate chains could be easily detected. We also examined the presence of lectins in the crude extract of tulip bulbs and determined the detailed carbohydrate-binding specificity of Tulipa gesneriana agglutinin (TGA), one of the lectins from tulip bulbs. Kinetic studies demonstrated that TGA showed novel carbohydrate-binding specificity and preferentially recognized triantennary oligosaccharides with Gal residues at nonreducing termini and a Fuc residue linked through alpha(1-6) linkage at chitobiose portion of the reducing termini but not tetraantennary carbohydrates. The results described here indicate that CAE will be a valuable method for both screening of lectins in natural sources and determination of their detailed carbohydrate-binding specificities.
Sille Ehala - One of the best experts on this subject based on the ideXlab platform.
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Application of Capillary Affinity Electrophoresis and density functional theory to the investigation of valinomycin-lithium complex.
Journal of chromatography. A, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:Abstract Capillary Affinity Electrophoresis (CAE) and quantum mechanical density functional theory (DFT) have been applied to the investigation of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with lithium cation Li + . Firstly, from the dependence of effective electrophoretic mobility of Val on the Li + ion concentration in the background electrolyte (BGE) (methanolic solution of 50 mM chloroacetic acid, 25 mM Tris, pH MeOH 7.8, 0–40 mM LiCl), the apparent binding (stability) constant ( K b ) of Val–Li + complex in methanol was evaluated as log K b = 1.50 ± 0.24. The employed CAE method include correction of the effective mobilities measured at ambient temperature, at different input power (Joule heating) and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25 °C and to the constant ionic strength 25 mM. Secondly, using DFT calculations, the most probable structures of the non-hydrated Val–Li + and hydrated Val–Li + ·3H 2 O complex species were predicted.
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Capillary Affinity Electrophoresis and ab initio calculation studies of valinomycin complexation
2009Co-Authors: Sille Ehala, Emanuel MakrlkAbstract:complex was evaluated experi-mentally by means of Capillary Affinity Electrophoresis. From the dependence ofvalinomycin effective electrophoretic mobility on the sodium ion concentration inthe BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, 0–40 mMNaCl), the apparent binding (stability) constant (K
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Capillary Affinity Electrophoresis and ab initio calculation studies of valinomycin complexation with Na+ ion.
Journal of separation science, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:In a combined experimental and theoretical approach, the interactions of valinomycin (Val), macrocyclic depsipeptide antibiotic ionophore, with sodium cation Na+ have been investigated. The strength of the Val–Na+ complex was evaluated experimentally by means of Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the sodium ion concentration in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, 0–40 mM NaCl), the apparent binding (stability) constant (Kb) of the Val–Na+ complex in methanol was evaluated as log Kb = 1.71 ± 0.16. Besides, using quantum mechanical density functional theory (DFT) calculations, the most probable structures of the nonhydrated Val–Na+ as well as hydrated Val–Na+·H2O complex species were proposed. Compared to Val–Na+, the optimized structure of Val–Na+·H2O complex appears to be more realistic as follows from the substantially higher binding energy (118.4 kcal/mol) of the hydrated complex than that of the nonhydrated complex (102.8 kcal/mol). In the hydrated complex, the central Na+ cation is bound by strong bonds to one oxygen atom of the respective water molecule and to four oxygens of the corresponding C=O groups of the parent valinomycin ligand.
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Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation
Electrophoresis, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb + . Capillary Affinity Electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb + complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb + cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb + cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K b ) of the Val-Rb + complex in methanol was evaluated as log K b = 4.63±0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of val-Rb + complex, Val is stabilized by strong non-covalent bond interactions of Rb + with six ester carbonyl oxygen atoms so that the position of the "central" Rb + cation in the Val cage is symmetric.
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Theoretical and experimental study of the complexation of valinomycin with ammonium cation.
Biopolymers, 2008Co-Authors: Jiří Dybal, Sille Ehala, Václav Kašička, Emanuel MakrlíkAbstract:The interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with ammonium cation NH4+ have been investigated. Using quantum mechanical density functional theory (DFT) calculations, the most probable structure of the valinomycin-NH4+ complex species was predicted. In this complex, the ammonium cation is bound partly by three strong hydrogen bonds to three ester carbonyl oxygen atoms of valinomycin and partly by somewhat weaker hydrogen bonds to the remaining three ester carbonyl groups of the valinomycin ligand. The strength of the valinomycin-NH4+ complex was evaluated experimentally by Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the ammonium ion concentration in the background electrolyte, the apparent binding (association, stability) constant (Kb) of the valinomycin-NH4+ complex in methanol was evaluated as log Kb = 1.52 ± 0.22. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1055–1060, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Václav Kašička - One of the best experts on this subject based on the ideXlab platform.
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Application of Capillary Affinity Electrophoresis and density functional theory to the investigation of valinomycin-lithium complex.
Journal of chromatography. A, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:Abstract Capillary Affinity Electrophoresis (CAE) and quantum mechanical density functional theory (DFT) have been applied to the investigation of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with lithium cation Li + . Firstly, from the dependence of effective electrophoretic mobility of Val on the Li + ion concentration in the background electrolyte (BGE) (methanolic solution of 50 mM chloroacetic acid, 25 mM Tris, pH MeOH 7.8, 0–40 mM LiCl), the apparent binding (stability) constant ( K b ) of Val–Li + complex in methanol was evaluated as log K b = 1.50 ± 0.24. The employed CAE method include correction of the effective mobilities measured at ambient temperature, at different input power (Joule heating) and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25 °C and to the constant ionic strength 25 mM. Secondly, using DFT calculations, the most probable structures of the non-hydrated Val–Li + and hydrated Val–Li + ·3H 2 O complex species were predicted.
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Capillary Affinity Electrophoresis and ab initio calculation studies of valinomycin complexation with Na+ ion.
Journal of separation science, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:In a combined experimental and theoretical approach, the interactions of valinomycin (Val), macrocyclic depsipeptide antibiotic ionophore, with sodium cation Na+ have been investigated. The strength of the Val–Na+ complex was evaluated experimentally by means of Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the sodium ion concentration in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, 0–40 mM NaCl), the apparent binding (stability) constant (Kb) of the Val–Na+ complex in methanol was evaluated as log Kb = 1.71 ± 0.16. Besides, using quantum mechanical density functional theory (DFT) calculations, the most probable structures of the nonhydrated Val–Na+ as well as hydrated Val–Na+·H2O complex species were proposed. Compared to Val–Na+, the optimized structure of Val–Na+·H2O complex appears to be more realistic as follows from the substantially higher binding energy (118.4 kcal/mol) of the hydrated complex than that of the nonhydrated complex (102.8 kcal/mol). In the hydrated complex, the central Na+ cation is bound by strong bonds to one oxygen atom of the respective water molecule and to four oxygens of the corresponding C=O groups of the parent valinomycin ligand.
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Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation
Electrophoresis, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb + . Capillary Affinity Electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb + complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb + cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb + cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K b ) of the Val-Rb + complex in methanol was evaluated as log K b = 4.63±0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of val-Rb + complex, Val is stabilized by strong non-covalent bond interactions of Rb + with six ester carbonyl oxygen atoms so that the position of the "central" Rb + cation in the Val cage is symmetric.
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Theoretical and experimental study of the complexation of valinomycin with ammonium cation.
Biopolymers, 2008Co-Authors: Jiří Dybal, Sille Ehala, Václav Kašička, Emanuel MakrlíkAbstract:The interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with ammonium cation NH4+ have been investigated. Using quantum mechanical density functional theory (DFT) calculations, the most probable structure of the valinomycin-NH4+ complex species was predicted. In this complex, the ammonium cation is bound partly by three strong hydrogen bonds to three ester carbonyl oxygen atoms of valinomycin and partly by somewhat weaker hydrogen bonds to the remaining three ester carbonyl groups of the valinomycin ligand. The strength of the valinomycin-NH4+ complex was evaluated experimentally by Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the ammonium ion concentration in the background electrolyte, the apparent binding (association, stability) constant (Kb) of the valinomycin-NH4+ complex in methanol was evaluated as log Kb = 1.52 ± 0.22. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1055–1060, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
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Determination of stability constants of valinomycin complexes with ammonium and alkali metal ions by Capillary Affinity Electrophoresis.
Electrophoresis, 2008Co-Authors: Sille Ehala, Václav Kašička, Emanuel MakrlíkAbstract:Capillary Affinity Electrophoresis (CAE) has been employed to investigate quantitatively the interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with univalent cations, ammonium and alkali metal ions, K + , Cs + , Na + , and Li + , in methanol. The study involved measuring the change in effective electrophoretic mobility of valinomycin while the cation concentrations in the BGE were increased. The corresponding apparent stability (binding) constants of the valinomycin-univalent cation complexes were obtained from the dependence of valinomycin effective mobility on the cation concentration in BGE using a nonlinear regression analysis. The calculated apparent stability constants of the above-mentioned complexes show the substantially higher selectivity of valinomycin for K + and Cs + ions over Li + , Na + , and NH 4 + ions. CAE proved to be a suitable method for the investigation of both weak and strong interactions of valinomycin with small ions.
Emanuel Makrlík - One of the best experts on this subject based on the ideXlab platform.
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Application of Capillary Affinity Electrophoresis and density functional theory to the investigation of valinomycin-lithium complex.
Journal of chromatography. A, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:Abstract Capillary Affinity Electrophoresis (CAE) and quantum mechanical density functional theory (DFT) have been applied to the investigation of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with lithium cation Li + . Firstly, from the dependence of effective electrophoretic mobility of Val on the Li + ion concentration in the background electrolyte (BGE) (methanolic solution of 50 mM chloroacetic acid, 25 mM Tris, pH MeOH 7.8, 0–40 mM LiCl), the apparent binding (stability) constant ( K b ) of Val–Li + complex in methanol was evaluated as log K b = 1.50 ± 0.24. The employed CAE method include correction of the effective mobilities measured at ambient temperature, at different input power (Joule heating) and at variable ionic strength of the BGEs to the mobilities related to the reference temperature 25 °C and to the constant ionic strength 25 mM. Secondly, using DFT calculations, the most probable structures of the non-hydrated Val–Li + and hydrated Val–Li + ·3H 2 O complex species were predicted.
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Capillary Affinity Electrophoresis and ab initio calculation studies of valinomycin complexation with Na+ ion.
Journal of separation science, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:In a combined experimental and theoretical approach, the interactions of valinomycin (Val), macrocyclic depsipeptide antibiotic ionophore, with sodium cation Na+ have been investigated. The strength of the Val–Na+ complex was evaluated experimentally by means of Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the sodium ion concentration in the BGE (methanolic solution of 20 mM chloroacetic acid, 10 mM Tris, 0–40 mM NaCl), the apparent binding (stability) constant (Kb) of the Val–Na+ complex in methanol was evaluated as log Kb = 1.71 ± 0.16. Besides, using quantum mechanical density functional theory (DFT) calculations, the most probable structures of the nonhydrated Val–Na+ as well as hydrated Val–Na+·H2O complex species were proposed. Compared to Val–Na+, the optimized structure of Val–Na+·H2O complex appears to be more realistic as follows from the substantially higher binding energy (118.4 kcal/mol) of the hydrated complex than that of the nonhydrated complex (102.8 kcal/mol). In the hydrated complex, the central Na+ cation is bound by strong bonds to one oxygen atom of the respective water molecule and to four oxygens of the corresponding C=O groups of the parent valinomycin ligand.
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Capillary electrophoretic and computational study of the complexation of valinomycin with rubidium cation
Electrophoresis, 2009Co-Authors: Sille Ehala, Emanuel Makrlík, Jiří Dybal, Václav KašičkaAbstract:This study is focused on the characterization of interactions of valinomycin (Val), a macrocyclic dodecadepsipeptide antibiotic ionophore, with rubidium cation, Rb + . Capillary Affinity Electrophoresis was employed for the experimental evaluation of the strength of the Val-Rb + complex. The study involved the measurement of the change of effective electrophoretic mobility of Val at increasing concentration of Rb + cation in the BGE. From the dependence of Val effective electrophoretic mobility on the Rb + cation concentration in the BGE (methanolic solution of 100 mM Tris, 50 mM acetic acid, 0-1 mM RbCl), the apparent binding (stability) constant (K b ) of the Val-Rb + complex in methanol was evaluated as log K b = 4.63±0.27. According to the quantum mechanical density functional theory calculations employed to predict the most probable structure of val-Rb + complex, Val is stabilized by strong non-covalent bond interactions of Rb + with six ester carbonyl oxygen atoms so that the position of the "central" Rb + cation in the Val cage is symmetric.
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Theoretical and experimental study of the complexation of valinomycin with ammonium cation.
Biopolymers, 2008Co-Authors: Jiří Dybal, Sille Ehala, Václav Kašička, Emanuel MakrlíkAbstract:The interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with ammonium cation NH4+ have been investigated. Using quantum mechanical density functional theory (DFT) calculations, the most probable structure of the valinomycin-NH4+ complex species was predicted. In this complex, the ammonium cation is bound partly by three strong hydrogen bonds to three ester carbonyl oxygen atoms of valinomycin and partly by somewhat weaker hydrogen bonds to the remaining three ester carbonyl groups of the valinomycin ligand. The strength of the valinomycin-NH4+ complex was evaluated experimentally by Capillary Affinity Electrophoresis. From the dependence of valinomycin effective electrophoretic mobility on the ammonium ion concentration in the background electrolyte, the apparent binding (association, stability) constant (Kb) of the valinomycin-NH4+ complex in methanol was evaluated as log Kb = 1.52 ± 0.22. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1055–1060, 2008. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
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Determination of stability constants of valinomycin complexes with ammonium and alkali metal ions by Capillary Affinity Electrophoresis.
Electrophoresis, 2008Co-Authors: Sille Ehala, Václav Kašička, Emanuel MakrlíkAbstract:Capillary Affinity Electrophoresis (CAE) has been employed to investigate quantitatively the interactions of valinomycin, macrocyclic depsipeptide antibiotic ionophore, with univalent cations, ammonium and alkali metal ions, K + , Cs + , Na + , and Li + , in methanol. The study involved measuring the change in effective electrophoretic mobility of valinomycin while the cation concentrations in the BGE were increased. The corresponding apparent stability (binding) constants of the valinomycin-univalent cation complexes were obtained from the dependence of valinomycin effective mobility on the cation concentration in BGE using a nonlinear regression analysis. The calculated apparent stability constants of the above-mentioned complexes show the substantially higher selectivity of valinomycin for K + and Cs + ions over Li + , Na + , and NH 4 + ions. CAE proved to be a suitable method for the investigation of both weak and strong interactions of valinomycin with small ions.
