Interactions of dipeptides with Triton X-100 in aqueous solution: A volumetric and spectroscopic study

The interactions of dipeptides with Triton X-100 in aqueous solution have been investigated by means of density, fluorescence spectroscopy and UV-vis spectroscopy. The standard partial molar volume (V2,ϕo), standard partial molar volume of transfer for dipeptide from water to aqueous Triton X-100 solution (ΔtVo) and partial molar expansibility (Eϕo) have been calculated from density data. Fluorescence spectroscopy was used to estimate the critical micellar concentration (ccmc) and micelle aggregation number of Triton X-100 in aqueous dipeptide solutions. Effects of temperature and hydrocarbon chain length of dipeptides on the volumetric properties of dipeptide and critical micelle concentration (ccmc) of Triton X-100 were examined. The pyrene fluorescence spectra were also used to study the change of micropolarity produced by the interactions of Triton X-100 with dipeptides. From the results of UV-vis absorption spectra, the binding constant between dipeptide and Triton X-100 above the ccmc was determined. The results have been interpreted in terms of solute-solvent interactions and structural changes in the mixed solutions.