Direct Measurement of the Thermodynamics of Chiral Recognition in Bile Salt Micelles
Isothermal titration calorimetry (ITC) is shown to be a sensitive reporter of bile salt micellization and chiral recognition. Detailed ITC characterization of bile micelle formation as well as the chiral recognition capabilities of sodium cholate (NaC), deoxycholate (NaDC), and taurodeoxycholate (NaTDC) micelle systems are reported. The ΔHdemic of these bile salt micelle systems is directly observable and is strongly temperature-dependent, allowing also for the determination of ΔCpdemic. Using the pseudo-phase separation model, ΔGdemic and TΔSdemic were also calculated. Chirally selective guest–host binding of model racemic compounds 1,1’-bi-2-napthol (BN) and 1,1’-binaphthyl-2,2’-diylhydrogenphosphate (BNDHP) to bile salt micelles was then investigated. The S-isomer was shown to bind more tightly to the bile salt micelles in all cases. A model was developed that allows for the quantitative determination of the enthalpic difference in binding affinity that corresponds to chiral selectivity, which is on the order of 1 kJ mol-1.
Anderson, Shauna Lynn; Rovnyak, David; and Strein, Timothy. "Direct Measurement of the Thermodynamics of Chiral Recognition in Bile Salt Micelles." Chirality 28, no. 4 (2016) : 290-298.