Interaction between gastric enzyme pepsin and tetradecyltrimethylammonium bromide in presence of sodium electrolytes: Exploration of micellization behavior.

Pepsin is a proteolytic enzyme used in the treatment of digestive disorders. In this study, we investigated the physicochemical properties of the tetradecyltrimethylammonium bromide (TTAB) and pepsin protein mixture in various sodium salt media within a temperature range of 300.55-320.55 K with 5 K intervals. The conductometric study of the TTAB+pepsin mixture revealed a reduction in the critical micelle concentration (CMC) in electrolyte media. The micellization of TTAB was delayed in the presence of pepsin. The CMC of the TTAB + pepsin mixture was found to depend on the concentrations of electrolytes and protein, as well as the temperature variations. The aggregation of the TTAB+pepsin mixture was hindered as a function of [pepsin] and increasing temperatures, while micellization was promoted in aqueous electrolyte solutions. The negative free energy changes (∆Gm0) indicated the spontaneous aggregation of the TTAB+pepsin mixture. Changes in enthalpy, entropy, molar heat capacities, transfer properties, and enthalpy-entropy compensation variables were calculated and illustrated rationally. The interaction forces between TTAB and pepsin protein in the experimental solvents were primarily hydrophobic and electrostatic (ion-dipole) in nature. An analysis of molecular docking revealed hydrophobic interactions as the main stabilizing forces in the TTAB-pepsin complex.