Mixed Aggregates of Surface-Active Ionic Liquids and 14-2-14 Gemini Surfactants in an Aqueous Medium as Fluid Scaffolds for Enzymology of Cytochrome-c

The aggregation behavior of the surface-active ionicliquid (SAIL),3-(2-(hexadecyloxy)-2-oxoethyl)-1-methyl-1H-imidazol-3-iumchloride, [C(16)Emim][Cl], and a gemini surfactant (GS) (14-2-14)in the whole mole fraction range has been investigated in an aqueousmedium employing various techniques. Experimentally obtained valuesof critical aggregation concentration (cac) are in good agreementwith the theoretical cac values obtained using Clint's equation.Rubingh's model has been employed to evaluate the extent ofsynergistic interactions between two components, which has been foundto be dependent upon the composition of a mixture of surfactants.The polarity index, hydrodynamic diameter (D (h)), zeta potential (& zeta;-Pot.), and morphology of the aggregateshave been found to be dependent upon the extent of hydrophobic aswell as dipolar interactions and the degree of counterion bindinggoverned by the content of the GS in mixed aggregates. Thermodynamicparameters evaluated employing isothermal titration calorimetry haverevealed the aggregation as an entropy-driven process. Density functionaltheory calculations provide a detailed account of the SAIL-GSinteractions at the molecular level. The reduced density gradient(RDG)along with the calculated isosurfaces asserts that the dominant interactionsare noncovalent interactions. Furthermore, the enzymology of cytochrome-cin the aqueous SAIL-GS aggregated systems has been investigatedand a two-fold increase in the enzyme activity has been observed inthe aggregates formed by the GS as compared to that in buffer.

Automated summary

The aggregation behavior of the SAIL and GS in aqueous medium has been studied using various techniques. The extent of synergistic interactions between the components depends on the composition of the surfactant mixture. The properties of the aggregates are influenced by hydrophobic and dipolar interactions, as well as counterion binding.