The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Hajime Namikoshi - One of the best experts on this subject based on the ideXlab platform.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (beta-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45 degrees C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (beta-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (beta-1,3-glucan) and cellulose (beta-1,4-glucan) with different sugar linkages.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (β-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45°C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (β-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (β-1,3-glucan) and cellulose (β-1,4-glucan) with different sugar linkages. Chirality 16:272–276, 2004. © 2004 Wiley-Liss, Inc.
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Dependence of Chiral Recognition on the degree of substitution of cellulose benzoate
Cellulose, 2004Co-Authors: Yuzo Toga, Hajime Namikoshi, Kenji Hioki, Tohru ShibataAbstract:A series of cellulose benzoates with different degrees of substitution (DS) were prepared by aminolysis under homogeneous conditions. Using them as a stationary phase, the dependence of the chromatographic Chiral Recognition of cellulose benzoate (CB) on its DS was studied under normal phase conditions. For most enantiomeric pairs, Chiral Recognition decreased along with the decrease in DS. However, some enantiomeric pairs were resolved only by CBs carrying unsubstituted hydroxyl groups. Many of the compounds were quite strongly retained by cellulose benzoate with a DS of 2.8. A study of the retention behaviors of simple aChiral compounds led us to the conclusion that the change in the retention behaviors by introducing free hydroxyl groups into tribenzoate is not caused by hydrogen bonding including the hydroxyl groups, but by a specific unidentified change.
Yun-bao Jiang - One of the best experts on this subject based on the ideXlab platform.
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Balancing interactions in proline-based receptors for Chiral Recognition of L-/D-DOPA
Organic & biomolecular chemistry, 2020Co-Authors: Lin-e Guo, Yuan Hong, Shu-ying Zhang, Xiao-sheng Yan, Yu-xin Tang, Yun-bao JiangAbstract:Proline based receptors (1-14) attached with phenylboronic acid and benzaldehyde binding groups at the N-/C- or C-/N-termini of the proline residue were created for Chiral Recognition of l-/d-DOPA, in an attempt to examine if balancing the two binding events would influence the Recognition. By changing the positions of boronic acid and aldehyde groups substituted on the phenyl rings (1-4, 5-8) and the site at which phenylboronic acid and benzaldehyde moieties attached respectively to the N- and C-termini or C- and N-termini of the proline residue (1-4vs.5-8), and by introducing an electron-withdrawing fluorine atom in the phenyl ring of the weaker binder the benzaldehyde moiety (11vs.1, 14vs.5), we were able to show that a better balance of the two binding events does improve the Chiral Recognition. This finding can only be made with the current version of receptors that were equipped with two different binding groups. Together with the finding that the Chiral Recognition performance in mixed organic-aqueous solutions is tunable by varying the solvent composition, we have now arrived at a protocol for designing proline based receptors for extended applications in Chiral Recognition.
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Proline-Based Boronic Acid Receptors for Chiral Recognition of Glucose.
The Journal of organic chemistry, 2018Co-Authors: Lin-e Guo, Yuan Hong, Shu-ying Zhang, Miao Zhang, Xiao-sheng Yan, Jinlian Cao, Tony D. James, Yun-bao JiangAbstract:Chiral Recognition remains a major challenge in the area of molecular receptor design. With this research, we set out to explore the use of proline-based receptors for Chiral Recognition. Importantly, the proline structure allows for the introduction of at least two different binding groups due to the availability of both an amine and carboxylic acid group. Here we report a proof-of-concept exploration into the Chiral Recognition of d/l-glucose as a model Chiral species, which prefers to bind to at least two boronic acid groups. We evaluated several proline-based receptors incorporating two phenylboronic acid groups, respectively, at the N- and C-termini of the amino acid residue, via amide bonds. We confirmed that the receptors exhibited Chiral Recognition using CD, 1H NMR, and 19F NMR spectroscopy. Given the derivation diversity available, our strategy to use proline-based receptors for Chiral Recognition holds significant promise for extension to other Chiral systems.
Yuzo Toga - One of the best experts on this subject based on the ideXlab platform.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (beta-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45 degrees C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (beta-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (beta-1,3-glucan) and cellulose (beta-1,4-glucan) with different sugar linkages.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (β-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45°C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (β-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (β-1,3-glucan) and cellulose (β-1,4-glucan) with different sugar linkages. Chirality 16:272–276, 2004. © 2004 Wiley-Liss, Inc.
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Dependence of Chiral Recognition on the degree of substitution of cellulose benzoate
Cellulose, 2004Co-Authors: Yuzo Toga, Hajime Namikoshi, Kenji Hioki, Tohru ShibataAbstract:A series of cellulose benzoates with different degrees of substitution (DS) were prepared by aminolysis under homogeneous conditions. Using them as a stationary phase, the dependence of the chromatographic Chiral Recognition of cellulose benzoate (CB) on its DS was studied under normal phase conditions. For most enantiomeric pairs, Chiral Recognition decreased along with the decrease in DS. However, some enantiomeric pairs were resolved only by CBs carrying unsubstituted hydroxyl groups. Many of the compounds were quite strongly retained by cellulose benzoate with a DS of 2.8. A study of the retention behaviors of simple aChiral compounds led us to the conclusion that the change in the retention behaviors by introducing free hydroxyl groups into tribenzoate is not caused by hydrogen bonding including the hydroxyl groups, but by a specific unidentified change.
Masakazu Yoshikawa - One of the best experts on this subject based on the ideXlab platform.
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Chiral Recognition ability of oligopeptide derivatives consisting of glutamyl residues
Journal of Applied Polymer Science, 2005Co-Authors: Masakazu Yoshikawa, Yasuharu Nagai, Koji Moriguchi, Satoshi HiraokaAbstract:The effect of the constituting amino acid residue [Glu(OBzl)] number on the Chiral Recognition ability was investigated. Chiral Recognition sites were prepared from oligopeptide derivatives (constituting amino acid residue number = three–five) by adopting alternative molecular imprinting. It was made clear that with a constituting amino acid residue number of four, the tetrapeptide derivative of Glu(OBzl) is the best candidate material to generate a Chiral Recognition site among eight types of oligopeptide derivatives in the study. The affinity constant between Ac-L-Trp and a Chiral Recognition site ranged from 3.4 × 103 to 1.08 × 104 mol−1 dm3, depending on the number of Glu(OBzl) residues in an oligopeptide derivative. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1302–1309, 2005
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Chiral Recognition sites from carbonyldioxyglyceryl moiety by an alternative molecular imprinting
Sensors and Actuators B: Chemical, 2005Co-Authors: Masakazu Yoshikawa, Naosuke Hotta, Junji Kyoumura, Yusuke Osagawa, Takashi AokiAbstract:Abstract A novel candidate polymeric material bearing 5-membered cyclic carbonate moiety, poly[(2-oxo-1,3-dioxolan-4-yl)methyl methacrylate-co-acrylonitrile], was converted into a Chiral Recognition material by adopting Ac- d -Trp or Ac- l -Trp as a print molecule. The molecularly imprinted polymer showed Chiral Recognition ability, and the material imprinted by the d -isomer of Ac-Trp recognized the d -isomer in preference to the corresponding l -isomer and vice versa. The formation of the Chiral Recognition site was confirmed by the apparent adsorption isotherms of the molecularly imprinted materials.
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Effect of constituting amino acid residue numbers on molecularly imprinted Chiral Recognition sites.
Chirality, 2003Co-Authors: Yoshiko Kondo, Yukihiro Morita, Atushi Fujimoto, Masahiko Tounai, Satoshi Kimura, Masakazu YoshikawaAbstract:In the present study, the effect of constituting amino acid residue numbers of oligopeptide derivatives, which are candidate materials to construct molecular Recognition sites, on Chiral Recognition ability was investigated. Chiral Recognition sites were formed from oligopeptide derivatives, of which constituting amino acid residue numbers were three to six, by adopting an alternative molecular imprinting. It was made clear that the number four, in other words, the tetrapeptide derivative, is the best candidate material to form a Chiral Recognition site.
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Chiral Recognition Sites Converted from Tetrapeptide Derivatives Adopting Racemates as Print Molecules
Macromolecular Bioscience, 2003Co-Authors: Masakazu Yoshikawa, Jun-ichiro IzumiAbstract:Molecularly imprinted polymeric membranes were prepared from polystyrene resin bearing tetrapeptide derivatives H-Asp(OcHex)-Leu-Asp(OcHex)-Glu(OBzl)-OCH 2 - (DLDE) consisting of D-amino acid residues or L-amino acid residues. The tetrapeptide derivatives were converted into Chiral Recognition sites by using not only an optically pure Boc-Trp but also racemic Boc-Trps as a print molecule. The Chiral Recognition ability depends on the combination of the absolute configuration of the print molecule and that of constituting amino acid residues. The membrane prepared from a DLDE derivative consisting of D-amino acid residues and imprinted by Boc-D-Trp recognized the D-isomer in preference to the corresponding L-isomer and vice versa. In the present study, it was also made clear that racemic print molecules were effective in generating Chiral Recognition sites. The affinity constant of the generated Chiral Recognition site was determined to be 9.6 × 10 3 mol -1 . dm 3 , which was independent of the molecular imprinting conditions. Enantioselective permeation was attained by applying electrodialysis. An optimum perm-selectivity of 5.9, which corresponds to the adsorption selectivity, was attained.
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Novel polymeric membranes having Chiral Recognition sites converted from tripeptide derivatives
The Analyst, 2001Co-Authors: Masakazu Yoshikawa, Akira Shimada, Jun-ichiro IzumiAbstract:Six kinds of tripeptide derivative consisting of L-glutamic acid γ-benzyl ester [Glu(OBzl)] (E) and L-phenylalanine (Phe) (F), i.e. EEF, EFE, FEE, FEF, FFE and FFF, were converted into Chiral Recognition sites by adopting Boc-L-Trp as a print molecule. The formed Chiral Recognition sites discriminated between Ac-L-Trp and the corresponding D-isomer, and the L-isomer was incorporated into the membrane in preference to the D-isomer. The affinity constants between the Recognition site formed in each membrane and Ac-L-Trp were determined to be 9.6 × 103 to 8.4 × 103 mol−1 dm3. The affinity constant depends on both the tripeptide sequence and the amino acid residue content. Tripeptide derivatives containing more glutamic acid derivative residues or glutamic acid derivative as an amino-terminal residue show higher affinity constants.
Tohru Shibata - One of the best experts on this subject based on the ideXlab platform.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (beta-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45 degrees C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (beta-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (beta-1,3-glucan) and cellulose (beta-1,4-glucan) with different sugar linkages.
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Chiral Recognition ability of curdlan triacetate: solvent and temperature effects.
Chirality, 2004Co-Authors: Yuzo Toga, Akito Ichida, Tohru Shibata, Kozo Tachibana, Hajime NamikoshiAbstract:The Chiral Recognition ability of the Chiral stationary phase (CSP) consisting of curdlan (β-1,3-glucan) triacetate coated on silica gel was clearly changed by the contacting solvents and heat treatment. The Chiral Recognition ability significantly decreased, particularly at temperatures above 45°C, depending on the racemates. The molecular weight of the curdlan triacetate slightly influenced its ability. The Recognition abilities of curdlan tricetate that was lost by heat treatment were partially recovered by contact with methanol. However, when it was contacted with ethanol a different selectivity was observed. The labile Chiral Recognition ability of curdlan triacetate is in striking contrast to the very stable Chiral Recognition of cellulose (β-1,4-glucan) triacetate (Chiralcel OA). This difference may be ascribed to the conformational stability of the acetates consisting of curdlan (β-1,3-glucan) and cellulose (β-1,4-glucan) with different sugar linkages. Chirality 16:272–276, 2004. © 2004 Wiley-Liss, Inc.
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Dependence of Chiral Recognition on the degree of substitution of cellulose benzoate
Cellulose, 2004Co-Authors: Yuzo Toga, Hajime Namikoshi, Kenji Hioki, Tohru ShibataAbstract:A series of cellulose benzoates with different degrees of substitution (DS) were prepared by aminolysis under homogeneous conditions. Using them as a stationary phase, the dependence of the chromatographic Chiral Recognition of cellulose benzoate (CB) on its DS was studied under normal phase conditions. For most enantiomeric pairs, Chiral Recognition decreased along with the decrease in DS. However, some enantiomeric pairs were resolved only by CBs carrying unsubstituted hydroxyl groups. Many of the compounds were quite strongly retained by cellulose benzoate with a DS of 2.8. A study of the retention behaviors of simple aChiral compounds led us to the conclusion that the change in the retention behaviors by introducing free hydroxyl groups into tribenzoate is not caused by hydrogen bonding including the hydroxyl groups, but by a specific unidentified change.