Aggregate formation in tauroursodeoxycholate solutions

• The hydrodynamic radii of simple TUDC micelles in 12–60 mM TUDC solutions were measured to be ∼15.4 Å.
• A kinetic dialysis technique was employed to determine the TUDC monomer concentrations in TUDC concentrations.
• The best curve-fitting to the kinetic dialysis data of a predicted relationship was obtained by a least-squares technique.
• The obtained equilibrium constant values indicate that the concentration of TUDC dimers is very high in dilute solutions.

The hydrodynamic radius (rH) values of simple tauroursodeoxycholate (TUDC) micelles formed between 12 mM and 60 mM TUDC solutions were measured using a laser light-scattering method to be nearly constant (∼15.4 Å). Additionally, a kinetic dialysis technique was employed to determine the TUDC monomer concentrations with respect to the total TUDC concentrations. According to the chemical equilibrium treatment, a relationship between the TUDC monomer concentrations and the total TUDC concentrations was derived. By using a least-squares technique, the best curve-fitting to the kinetic dialysis data of the relationship predicted by the mass-action model was obtained. The equilibrium constants were also quantified. Their values together with the light-scattering results indicate that both TUDC dimers and simple TUDC micelles are formed from TUDC monomers by hydrophobic interaction. Moreover, the concentration of TUDC dimers is much higher than the concentration of simple TUDC micelles in TUDC solutions.