Interaction of 8-anilino-1-naphthalenesulfonate with 2,6-di- O-methylcyclomaltoheptaose

Abstract

The interaction of 8-anilino-1-naphthalenesulfonate (ANS) with 2,6-di- O-methyl-cyclomaltoheptaose (2,6-DM-βCD) was investigated in a 0.1 M phosphate buffer at pH 7.4 by fluorescence spectrophotometry. Utilizing the fact that the fluorescence intensity of ANS increases in the presence of 2,6-DM-βCD, the thermodynamic parameters for inclusion complex formation were determined as follows: Δ D° = −10.3 kJ·mol −1 at 25°C, Δ H° = −13.4 kJ·mol −1, Δ S° = −10.9 J·deg −1·mol −1. The main driving force for the inclusion complex formation was considered to be the Van der Waals-London dispersion forces, while the contribution of the hydrophobic interaction was small. Also, from the measurements of proton nuclear magnetic resonance spectra and studies with Corey-Pauling-Koltun models, the probable structure was determined.