| Abstrakt: |
The binding behavior of sodium cholate, a trihydroxy hydrophobic bile salt, by a polyacrylamide resin with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant group was determined with varying buffer conditions and in the presence of 1,2-propanediol as a solvent perturbant. Binding constants extracted from the fit of the binding isotherms to the Langmuir equation were obtained at several temperatures. The temperature dependence of the binding behavior indicated that binding, in comparison with that of the dihydroxy chenodeoxycholate, was weaker due to a smaller positive entropic change, despite a lowered enthalpic barrier. Enthalpy-entropy compensation with a compensation temperature of 285-290 K, characteristic of processes involving water, was found to encompass both the cholate and chenodeoxycholate data under a wide variety of conditions. Previous studies with sodium chenodeoxycholate determined that loss of hydrophobic hydration within the resin dominated the thermodynamics of the binding process, but the observations with sodium cholate revealed that solvent liberation about the bile salt is also a contributor. |
