In vitro evaluation of the non-covalent interactions of hemoglobin with distinctively modified gemini surfactants: Effect of structural variation

Binding of surfactants to biomacromolecules is an active field of current interest at the interface of chemical biology and medicinal chemistry, owing to their diverse applications in industries, biomedical and cosmetic domains. In relevance to this, we have investigated the interactions of two distinctly modified green gemini surfactants (C-12-E2O-C-12 and C-14-E2O-C-14) with the heme protein hemoglobin (Hb) utilizing different state-of-the-art techniques. These surfactants are employed to explicate the effect of structural variation on the conformation of Hb. Complexation between Hb and C-12-E2O-C-12/C-14-E2O-C-14 were found to follow the same 1:1 stoichiometric pattern but with different binding constants (evaluated through fluorescence and electrochemical measurements). The UV-vis spectra showed the influence of C-12-E2O-C-12/C-14-E2O-C-14 on Hb, displaying a strong concentration-dependent fashion. Furthermore, pyrene, synchronous and 3-D fluorescence spectra of Hb depicted the possible alterations induced in its aromatic microenvironment upon C-12-E2O-C-12/C-14-E2O-C-14 complexation. Far-UV CD results revealed nominal changes in the secondary structure of the Hb while a considerable loss in tertiary structure was observed in the near-UV range, elucidating the formation of molten globule state. The best energy-docked structure in the molecular docking analysis revealed that C-12-E2O-C-12/C-14-E2O-C-14 preferred to bind in the hydrophobic cavity of Hb. Thus, this work provides a comprehensive inspection of Hb-C-12-E2O-C-12/C-14-E2O-C-14 interaction at the molecular level that can be extended potentially to other congeners, which is essential in determining their future use as excipients in pharmaceutical formulations and other related applications.