Host-guest inclusion complexes of RNA nucleosides inside aqueous cyclodextrins explored by physicochemical and spectroscopic methods

Stable host-guest inclusion complexes have been formed with guest RNA nucleosides inside aqueous alpha- and beta-cyclodextrins. alpha-Cyclodextrin has been found to have favorable structural features for inclusion with uridine and cytidine, whereas beta-cyclodextrin has that with all the four nucleosides, e.g., adenosine, guanosine, uridine and cytidine. The formation and nature of the inclusion complexes have been characterized using surface tension study, Job's method by ultraviolet spectroscopy and pH measurements. The limiting apparent molar volume, viscosity B-coefficient, limiting apparent molar adiabatic compressibility and limiting molar refraction data have been used to characterize the interaction between nucleosides and cyclodextrins in the experimental ternary solution systems. The inclusion phenomenon has been confirmed by proton NMR study. Association constants and thermodynamic parameters have been evaluated for the formed inclusion complexes by ultraviolet spectroscopy.