INTERACTIONS IN THE MODEL SYSTEM ALPHA-CYCLODEXTRIN-GLYCEROL - EXPERIMENTAL AND THEORETICAL-STUDY

The association between alpha-cyclodextrin and glycerol has been studi ed using experimental and theoretical methods. The experimental techni que used was microcalorimetric stepwise titration at 288.15, 298.15 an d 313.15 K. The formation of a 1:1 complex between alpha-cyclodextrin and glycerol, in aqueous solutions, is indicated. There was no tempera ture dependence of the observed parameters. The thermodynamic paramete rs were K = 1.34 +/- 0.07, Delta H degrees = (-3.1 +/- 0.1) kJ mol(-1) , Delta G degrees = (-0.7 +/- 0.1) kJ mol(-1) and Delta S degrees = (- 8 +/- 4) J K-1 mol(-1) (Gibbs energy and entropy values calculated for 298.15 K). Molecular dynamics simulations have also been carried out. The average structures, obtained from 100 ps of dynamics, are compare d with the solvated 'empty' alpha-cyclodextrin average structure. The dynamics calculations show that there is a structurally and energetica lly favourable association between the molecules, which is in good agr eement with the experimental findings.