Date of Thesis
Bile salts are understood to form micelles in order to perform their physiological function which is to emulsify dietary lipids, however the chemical nature of bile micelles is not well understood and is debated frequently in the literature. The objective of this thesis is to utilize a thermodynamic approach to investigate the chiral selection capabilities of bile salts and their micelle aggregation processes. In total, the micellar and chiral properties of six bile salts are assessed over a broad temperature range (273 to 313 K) utilizing isothermal titration calorimetry (ITC) and micellar electrokinetic chromatography (MEKC) techniques. Thermodynamic analysis of demicellization in cholate (CA), taurocholate (TC), glycocholate (GC), deoxycholate (DC), taurodeoxycholate (TDC), and chenodeoxycholate (CDC) systems directly reveals the enthalpy of demicellization (ΔHdemicel) and the critical micelle concentration (CMC). Modeling indirectly revealed the Gibbs free energy of demicellization (ΔGdemicel), the entropy of demicellization (TΔSdemicel), and the change in heat capacity of demicellization (ΔCp). Additionally, ITC allows the exploration of guest-host dynamics of (R,S)-1,1-binaphthyl-2,2’- diylhydrogenphosphate (BNDHP) with bile salt micelle systems. S-BNDHP is found to bind more strongly to the micelle in all but CDC micelles, and low temperature experimentation enhanced visualization of multiple aggregation steps in CA, TC, and GC systems. MEKC separations of R,S-BNDHP with bile salt buffer support the claim that differences in heat of binding (ΔΔHapp.bind) may predict the degree of chiral separation in MEKC. More work is necessary to investigate the presence of stepwise micelle aggregation in bile salt systems and to better characterize micellization and chiral guest-host binding at low temperatures.
bile salts, micelles, thermodynamics, isothermal titration calorimetry, capillary electrophoresis
Honors Thesis (Bucknell Access Only)
Bachelor of Science
Timothy G. Strein
Sussman, Chad B., "Thermodynamic Investigations of Chiral Selection with Bile Salt Micelles" (2019). Honors Theses. 483.