The paper reports the simultaneous fluorescence determination of D,L-tryptophanenantiomer by chiral recognition of β-cyclodextrin for the first time. Chiral discrimination isobserved for fluorescence emission of D- a...The paper reports the simultaneous fluorescence determination of D,L-tryptophanenantiomer by chiral recognition of β-cyclodextrin for the first time. Chiral discrimination isobserved for fluorescence emission of D- and L-tryptophan when complexed toβ-cyclodextrin, and is significantly related to reaction temperature, time and PH. The proposedenantiomeric resolution of D- and L-tryptophan is based on the non-fluorescellce emission ofLtryptophan in β-cyclodextrln solution at 35℃ and after 24 h standing by. The fluorescenceemission and absorbance of L-tryptophan disappear with the Increase of β-cyclodextrin at 35℃ and 24 h standing by, where as it is not observed for D-tryptophan. The detection limitsare 3.1×10-8 mol/L for D-tryptophan and 2.7 ×10-7 mol/L for L-tryptophan, respectively,with a RSD of 1. 0%-2. 6% (n=7). The method has been shown to be accurate with a ratioof 2%(molar ratio) of one enantiomer in the presence of the other. The observed pseudofirst-order rate constant is calculated. The reaction mechanism has been discussed usingpyrene as a fluorescence probe.展开更多
Mono（2-phenylseleno-2-deoxy）-β-cyclodextrin（2） and mono[2-（p-methoxyphenylseleno）-2-deoxy]-β-cyclodextrin（4）, were newly synthesized and characterized by combustion analyses, IR, 1H NMR and 13 C NMR. Spectro...Mono（2-phenylseleno-2-deoxy）-β-cyclodextrin（2） and mono[2-（p-methoxyphenylseleno）-2-deoxy]-β-cyclodextrin（4）, were newly synthesized and characterized by combustion analyses, IR, 1H NMR and 13 C NMR. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution（pH 7.20, 0.1 mol/L） at 25 ℃ to give the complex K S and -ΔG° for the stoichiometric 1∶1 inclusion complexation of mono（6-phenylseleno-6-deoxy）-β-cyclodextrin（1）, mono[6-（p-methoxyphenylseleno）-6-deoxy]-β-cyclodextrin（3） and the novel cyclodextrin derivatives 2 and 4 with L- and D-tryptophan. The molecular binding ability and selectivity for L- and D-tryptophan of modified β-cyclodextrins（14） are discussed from the size/shape-fit and geometrical complement relationships between the host cavity and the guest molecule. The results obtained indicate that van der Waals force and hydrophobic interactions dominate the complexation of 1—4 and the aromatic substituents introduced extend the original hydrophobicity of cavity and the molecular binding ability, but reduce the enantioselectivity for L/D-tryptophan guests.展开更多
文摘The paper reports the simultaneous fluorescence determination of D,L-tryptophanenantiomer by chiral recognition of β-cyclodextrin for the first time. Chiral discrimination isobserved for fluorescence emission of D- and L-tryptophan when complexed toβ-cyclodextrin, and is significantly related to reaction temperature, time and PH. The proposedenantiomeric resolution of D- and L-tryptophan is based on the non-fluorescellce emission ofLtryptophan in β-cyclodextrln solution at 35℃ and after 24 h standing by. The fluorescenceemission and absorbance of L-tryptophan disappear with the Increase of β-cyclodextrin at 35℃ and 24 h standing by, where as it is not observed for D-tryptophan. The detection limitsare 3.1×10-8 mol/L for D-tryptophan and 2.7 ×10-7 mol/L for L-tryptophan, respectively,with a RSD of 1. 0%-2. 6% (n=7). The method has been shown to be accurate with a ratioof 2%(molar ratio) of one enantiomer in the presence of the other. The observed pseudofirst-order rate constant is calculated. The reaction mechanism has been discussed usingpyrene as a fluorescence probe.
文摘Mono（2-phenylseleno-2-deoxy）-β-cyclodextrin（2） and mono[2-（p-methoxyphenylseleno）-2-deoxy]-β-cyclodextrin（4）, were newly synthesized and characterized by combustion analyses, IR, 1H NMR and 13 C NMR. Spectrofluorometric titrations have been performed in aqueous phosphate buffer solution（pH 7.20, 0.1 mol/L） at 25 ℃ to give the complex K S and -ΔG° for the stoichiometric 1∶1 inclusion complexation of mono（6-phenylseleno-6-deoxy）-β-cyclodextrin（1）, mono[6-（p-methoxyphenylseleno）-6-deoxy]-β-cyclodextrin（3） and the novel cyclodextrin derivatives 2 and 4 with L- and D-tryptophan. The molecular binding ability and selectivity for L- and D-tryptophan of modified β-cyclodextrins（14） are discussed from the size/shape-fit and geometrical complement relationships between the host cavity and the guest molecule. The results obtained indicate that van der Waals force and hydrophobic interactions dominate the complexation of 1—4 and the aromatic substituents introduced extend the original hydrophobicity of cavity and the molecular binding ability, but reduce the enantioselectivity for L/D-tryptophan guests.
