RIBOFLAVIN AS A POSSIBLE PROBE IN STUDIES OF MOLECULAR AGGREGATE MICROVISCOSITY

Fluorescence polarization studies, using riboflavin as a probe, were c onducted in a model fluid made up of 20:80 water-glycerin mixture. The viscosity of this medium and the fluorescence polarization of ribofla vin solubilized therein were determined at temperatures varying from 1 0 degrees C to 50 degrees C +/- 0.2 degrees C. The data obtained were used to analyze and characterize the overall fluidity, microviscosity and flow activation energy of the glycerin-water medium. The fluidity and microviscosity of this medium, though temperature dependent, showe d opposite tendencies. While the former showed an increase, the latter showed a decrease as the temperature is increased. The flow activatio n energy so obtained was 19.8 kJ mole(-1). This value is in good agree ment with Literature values obtained for some liposomes, vesicles and lipid bilayer aggregates of similar viscosity. (C) 1998 Elsevier Scien ce S.A.