These values are smaller than the value determined in chloroform (36 ± 3 mL mg -1 cm -1 ). However, no inference as to the polarity of the environment for OTPh binding in NaDC aggregates can be made from these data since no clear trend was observed for the molar absorptivity values of OTPh in solvents with different polarities (Figure ). The normalized emission spectra of OTPh in NaDC are blue shifted when compared to the spectrum in chloroform (Figure inset). In the presence of 50 mM NaDC and higher bile salt concentrations, the OTPh the emission spectra are the same indicating that the environment around OTPh does not change as the concentration of NaDC is increased above 50 mM.