The interaction of 8-anilinonaphthalene-1-sulfonate (ANS) with α-cyclodextrin was investigated in a 0.1M phosphate buffer at pH 7.4 by fluorescence spectrophotometry. Utilizing the fact that the fluorescence intensity of ANS increases in the presence of α-cyclodextrin, the thermodynamic parameters for inclusion complex formation were determined as folloews; ΔG°=-1.25kcal/mol at 25°C, ΔH°=-3.0kcal/mol, ΔS°=-5.8e.u. The driving force for the inclusion complex formation was cosidered to be the van der Waals-London dispersion force and hydrogen bonding between -SO-3 of ANS and the secondary hydroxyl groups of α-acyclodextrin.Also, from the measurements of proton nuclear magnetic resonance spectra and studies with Corey Pauling Koltun models, the probable structure was determined.
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Nishijo et al. (1991) studied this question.