Study on the inclusion behavior of p-sulfonatocalix[6]arene with propranolol by spectrofluorometry

The inclusion interaction between propranolol (PPL) and p-sulfonatocalix[6]arene (SCX6) was investigated by fluorescence and H-1 NMR spectroscopy. Influences of pH, temperature, ionic strength and the concentration of SCX6 were examined in detail. In phosphate buffer solution with pH 7.5, the fluorescence of PPL dramatically quenched upon addition of SCX6 revealing the formation of inclusion complexes between PPL and SCX6. The stoichiometric ratio was verified to be 1:1 by the continuous variation method. The inclusion constant of PPL-SCX6 complexes was calculated as 2.2 x 10(4) L/mol by the nonlinear curve fitting method. H-1 NMR titration spectra testified that the aliphatic chain of PPL may be partially penetrated into the hydrophobic cavity of SCX6. This was confirmed by molecular dynamics calculations. (C) 2012 Elsevier B.V. All rights reserved.