Trans-gauche isomerization in 1-octanol probed by Brillouin scattering spectroscopy

Solute-Solvent Interactions in Aqueous Solutions of Sulfobutyl Ether-β-cyclodextrin As Probed by UV-Raman and FTIR-ATR Analysis

A vibrational study by means of UV-Raman and FTIR-ATR measurements has been performed on sulfobutyl ether β-cyclodextrin (SBE-β-CD)-water solutions, as a function of concentration and temperature, with the aim to provide a molecular-scale explanation of the enhanced performances as carrier agent exhibited by this modified macrocycle with respect to natural cyclodextrin. The attention has been mainly paid to the modifications induced on the vibrational band assigned to the O-H stretching intramolecular mode, in turn related to the dynamical rearrangement occurring in the hydrogen bonding (HB) network of water molecules. The results of our measurements clearly showed a characteristic "structure-breaker" effect on the tetrahedral HB arrangements induced on water molecules by increasing of both temperature and solute concentration, allowing us to also extract thermodynamic parameters. These results could be a key step for a clearer understanding of the connection between the dynamical properties of hydration water and the complexing ability of this cyclodextrin derivative.

Vibrational Analysis of Molecular Interactions in Aqueous Glucose Solutions. Temperature and Concentration Effects

A vibrational analysis using FTIR and Raman spectroscopies was carried out on aqueous glucose solutions with a wide range of solute molar fractions and temperatures. The analysis was aimed at revealing structural changes in the local hydrogen-bonding (HB) network of liquid water, correlating these with the conservative properties of biomolecules, and comparing them with those of other sugars. The results of our measurements clearly show that the action of glucose is 2-fold; on one hand, there is a linkage with free hydroxyls of water; on the other, there is a slight lessening of the ordered (tetrahedral) H-bonded assembly of bulk H(2)O. These opposite effects do not balance each other, so the average HB interaction strength decreases on increasing glucose concentration. As a result, there is a reduction in the temperature dependence of solutions structure. In our opinion, this could be related to the low bioprotective action of this carbohydrate.