A guanosine biogel: Chiral separations in capillary electrophoresis and spectroscopic studies.

摘要

A 5'-guanosine monophosphate (5'-GMP) gel was investigated for use in chiral separations in capillary electrophoresis. Guanosine gels are tunable, as their viscosity and structure depend on monomer concentration, pH, temperature, and cation concentration. In low viscosity 5'-GMP gels, the 5'-GMP structures can act as chiral selectors in enantiomeric separations, due to the chiral nature of guanosine. 5'-GMP gels were used in attempts to separate RS-propranolol, DL-tryptophan, +/--ketoprofen, +/--flurbiprofen, and +/--hydrobenzoin. Baseline resolution was achieved for RS-propranolol and partial resolution was achieved for DL-tryptophan. Separation was not achieved for +/--ketoprofen, +/--flurbiprofen, or +/--hydrobenzoin. The differences in the efficiencies of these separations are a result of the structural differences in the five chiral molecules. It was determined that electrotatic, hydrophobic, and hydrogen bonding interactions play important roles in the association between the gel structures and enantiomers. These associations are crucial in enantiomeric separations, and determine the types of chiral molecules that can be separated using a 5'-GMP gel in capillary electrophoresis.; Fluorescence probe studies were performed to further investigate solute-gel interactions, as well as the structural organization of the gels, under a variety of conditions. The fluorescence emission of Prodan and the fluorescence anisotropy of perylene were used to probe the microenvironments present within the 5'-GMP gels, as a function of pH, temperature, and incubation time. These studies showed that the secondary structures in the gels are more ordered at pH 5 than at pH 7, and solute molecules associate with the less ordered structures more readily. The smaller, less ordered gel structures are more thermally stable than the more highly ordered gel structures, and the higher-ordered gels go through structural transitions during the melting process. The probe studies also showed that the gels are structurally stable over a one-week period. Absorbance circular dichroism studies showed that the gel structures are thermally reversible over a few hours. The tunable structure and organization, as well as the thermal reversibility of the gel structures, make guanosine gels unique among other chiral selectors that are more commonly used in capillary electrophoresis.