Inclusion Complex of n-Octyl -D-Glucopyranoside and -Cyclodextrin in Aqueous Solutions: Thermodynamic and Structural Characterization
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- 作者：Valé ; rie Bernat ; Catherine Ringard-Lefebvre ; Geneviè ; ve Le Bas ; Bruno Perly ; Florence Djedaï ; ni-Pilard ; Sylviane Lesieur
- 刊名：Langmuir
- 出版年：2008
- 出版时间：April 1, 2008
- 年：2008
- 卷：24
- 期：7
- 页码：3140 - 3149
- 全文大小：480K
- 年卷期：v.24,no.7(April 1, 2008)
- ISSN：1520-5827
文摘
Complex formation between octyl 
ars/beta2.gif" BORDER=0 ALIGN="middle">-D-glucopyranoside (OG) and ars/alpha.gif" BORDER=0>-cyclodextrin (ars/alpha.gif" BORDER=0>CD) was investigated on thebasis of three highly accurate and appropriate experimental techniques. First, surface tension measurements showedthat ars/alpha.gif" BORDER=0>CD directly acts on the surfactant monomers in the aqueous phase, leading to progressive depletion of theair-water interface with increasing cyclodextrin contents. Significant shift of OG critical micelle concentration (cmc)was consequently observed: the higher ars/alpha.gif" BORDER=0>CD concentration, the higher the cmc value. Experiments performed atsurfactant and cyclodextrin concentrations in the Gibbs regime of surface tension versus OG content were performedon one hand to establish Job's plot that showed 1:1 stoichiometry of the OG-ars/alpha.gif" BORDER=0>CD complex and on the other handto calculate the association constant found equal to (1.85 ± 0.35) × 103 L mol-1. An inclusion process of the surfactantalkyl residue within the cyclodextrin cavity was confirmed by one-dimensional 1H NMR, and the structure of the mixedassembly was extensively characterized by two-dimensional NOESY 1H NMR. OG penetrates ars/alpha.gif" BORDER=0>CD so that its hydrocarbonchain is embedded inside the cyclodextrin cavity, and its polar head as well as the ars/alpha.gif" BORDER=0>-methylene group emerges outsidethe ars/alpha.gif" BORDER=0>CD secondary face. Solubility behavior of the OG-ars/alpha.gif" BORDER=0>CD complex in a wide range of host-guest ratios andconcentrations was finally examined by turbidity recording and optical microscopy. At very low free cyclodextrinlevels in the solution, the complex presented high solubility behavior up to more than 70 mM. By increasing nonassociatedars/alpha.gif" BORDER=0>CD in the mixture, propensity of the cyclodextrin molecules to crystallize was observed at concentrations far belowthe 100 mM aqueous solubility of the pure cyclodextrin. The hexagonal shape of the crystals seen in the opticalmicroscopy images suggested they were, partially at least, composed of the solid complex.
ars/beta2.gif" BORDER=0 ALIGN="middle">-D-glucopyranoside (OG) and ars/alpha.gif" BORDER=0>-cyclodextrin (ars/alpha.gif" BORDER=0>CD) was investigated on thebasis of three highly accurate and appropriate experimental techniques. First, surface tension measurements showedthat ars/alpha.gif" BORDER=0>CD directly acts on the surfactant monomers in the aqueous phase, leading to progressive depletion of theair-water interface with increasing cyclodextrin contents. Significant shift of OG critical micelle concentration (cmc)was consequently observed: the higher ars/alpha.gif" BORDER=0>CD concentration, the higher the cmc value. Experiments performed atsurfactant and cyclodextrin concentrations in the Gibbs regime of surface tension versus OG content were performedon one hand to establish Job's plot that showed 1:1 stoichiometry of the OG-ars/alpha.gif" BORDER=0>CD complex and on the other handto calculate the association constant found equal to (1.85 ± 0.35) × 103 L mol-1. An inclusion process of the surfactantalkyl residue within the cyclodextrin cavity was confirmed by one-dimensional 1H NMR, and the structure of the mixedassembly was extensively characterized by two-dimensional NOESY 1H NMR. OG penetrates ars/alpha.gif" BORDER=0>CD so that its hydrocarbonchain is embedded inside the cyclodextrin cavity, and its polar head as well as the ars/alpha.gif" BORDER=0>-methylene group emerges outsidethe ars/alpha.gif" BORDER=0>CD secondary face. Solubility behavior of the OG-ars/alpha.gif" BORDER=0>CD complex in a wide range of host-guest ratios andconcentrations was finally examined by turbidity recording and optical microscopy. At very low free cyclodextrinlevels in the solution, the complex presented high solubility behavior up to more than 70 mM. By increasing nonassociatedars/alpha.gif" BORDER=0>CD in the mixture, propensity of the cyclodextrin molecules to crystallize was observed at concentrations far belowthe 100 mM aqueous solubility of the pure cyclodextrin. The hexagonal shape of the crystals seen in the opticalmicroscopy images suggested they were, partially at least, composed of the solid complex.