Physicochemical evaluation of interaction behavior of a series of biocompatible gemini surfactants with hemoglobin: Insights from spectroscopic and computational studies

In this study, we investigated the interaction behavior of biodegradable, cationic, oxy-diester functionalized gemini surfactants N1,N1,N14,N14-tetramethyl-2,13-dioxo-N1,N14-dialkyl-3,6,12-tetraoxateradecane-1,14-diaminium dichloride (in short Cm-E2O2-Cm, m = 12, 14 or 16 is the number of carbon atoms in the alkyl chain) with one of the most important proteins in red blood cells viz. hemoglobin. We employed a variety of in-vitro and in-silico methodologies, such as fluorescence, UV–vis, FT-IR and circular dichroism spectroscopies, DFT, molecular docking, and molecular dynamics simulations, to study these interactions. Our results show that the chain length of the surfactants have distinct implications for the interaction behavior, as evidenced by the estimated physical parameters, such as Kb and ∆G. The order of Kb values (0.24 × 103 < 3.11 ×103 < 5.85 × 103 M-1) is in accordance with the increasing alkyl chain length of the surfactants. The negative Gibbs free energy change values and their order, − 13.58 < −19.93 < −21.49, further support the spontaneity of interactions and the effect of alkyl chain length. Theoretical insight into the environment at the quantum mechanical level, binding site, and energy stability of the protein-surfactant interactions were produced by computational methods. This research contributes significantly to the field of knowledge concerning surfactants' effects on protein structure and behavior.