Structural alteration of myoglobin with two homologous cationic surfactants and effect of β-cyclodextrin: multifaceted insight and molecular docking study†
The binding interactions of two homologous cationic surfactants (CTAB and CPC) with myoglobin (Mb) have been investigated in detail by employing various physicochemical and multifaceted techniques, such as tensiometry, UV-visible spectroscopy, steady-state fluorometry, time-resolved fluorometry, synchronous spectroscopy, circular dichroism (CD) spectroscopy, dynamic light scattering (DLS), stopped flow kinetics and cyclic voltammetry (CV), at physiological pH and 298 K. The enthalpy changes for the Mb–surfactant interactions have been investigated through isothermal titration calorimetry (ITC) studies. The surfactant–Mb association kinetics has been examined by the stopped flow technique. The drastic changes in both the cathodic and anodic peak currents and secondary structural content of Mb even in the presence of low concentrations of CPC compared to CTAB reveals that CPC interacts more strongly with Mb than with CTAB. This clarifies the dominant role of the head group of the surfactant for the binding interactions with Mb. UV-visible and CD spectroscopy reveals the recovery of the Soret band of Mb from structurally deformed Mb through the use of β-CD. β-CD has also the ability to recover the native conformation of Mb from the unfolded one, which was confirmed by emission (steady state and time-resolved) spectroscopy and DLS studies. Overall, the effects of β-CD on denatured Mb result in recovery of its primitive conformation. The molecular docking study also elucidates the potential role of the head groups of the surfactant in the binding interactions with Mb and the effects of β-CD.