Gemini versus single-chain cationic surfactant-assisted unfolding of myoglobin and their ousting by β-cyclodextrin

Herein, by pursuing consilience among several methodologies (different spectroscopic, molecular docking, and density functional theory (DFT)), we report that surfactants (functionalized cationic gemini, C12-E2O2-C12, and single-chain surfactant, DTAC) instigated myoglobin (Mb) unfolding and subsequently beta-cyclodextrin (β-CD) induced refolding of this unfolded Mb via inclusion complex formation. Fluorescence and UV–vis results unveil weak binding of the cationics at low concentrations followed by stronger interaction at higher concentrations before reaching the saturation point. Furthermore, refolding of the unfolded Mb using β-CD appears to be a reversible process. However, Mb does not completely recover its structure on refolding. From far-UV circular dichroism (CD) analysis, it is apparent that the α-helical content of Mb decreases/increases during unfolding/refolding process, which is further corroborated by Fourier transform infrared spectroscopy (FT-IR) results. Furthermore, fluctuations in the tertiary structure of Mb were detected through near-UV CD. Synchronous fluorescence together with molecular docking unravels the greater contribution of Trp in the involved interactions. DFT also substantiated the abstraction of C12-E2O2-C12/DTAC by β-CD. Fluorescence, far-UV CD and docking confirm the existence of negligible interaction between Mb and β-CD. The susceptibility of unfolding/refolding of Mb is considerably higher in the case of gemini than DTAC. In light of these results, it is strongly suggested that this work may prove fruitful for protein renaturation studies, which may address the interrelated issues of the biotechnological sector for the production of effective/affordable folding aids that could also be used to treat diseases linked to genetically engineered cells, caused by protein misfolding/aggregation.