Analyzing the interaction between porcine serum albumin (PSA) and ester-functionalized cationic gemini surfactants

Abstract

Green gemini surfactants (m-E2-m) containing cleavable ester functionalities were allowed to interact with porcine serum albumin (PSA) and the binding mechanism along with concomitant physicochemical changes were analyzed using a multi-technique approach. Intrinsic fluorescence study reveals that the concerned gemini surfactants have a substantial affinity for PSA at a pH well above its isoelectric point. Static quenching is indicated by the relevant value of bimolecular quenching constant (kq). Synchronous, three-dimensional and pyrene fluorescence data depict the PSA−m-E2-m complex formation together with significant conformational changes induced in PSA. UV–vis studies are also indicative of ground state complexation involving the biomolecule and the amphiphile. Far-UV CD spectra indicate the stabilization of protein structure as deciphered by the increased α-helical content, whereas near-UV CD spectra signify a tertiary structure close to that of the native state. In order to validate the results obtained by fluorescence, cyclic voltammetry is employed, which unveils the formation of electrochemically inactive PSA−m-E2-m complex. Moreover, it is revealed that gemini with longer chain interacts more efficiently than the one with shorter chain owing to stronger hydrophobic forces. All these findings suggest that in future, the m-E2-m geminis may be potentially utilized as excipients in drug, skincare and immunoassay reagent formulations. Furthermore, results of this research work will also contribute in understanding the physicochemical effect of surfactant architecture on its interaction with biomacromolecules.