Binding interaction of sodium-N-dodecanoyl sarcosinate with hemoglobin and myoglobin: Physicochemical and...

The interaction of an amino acid surfactant, sodium-N-dodecanoyl sarcosinate (SDDS), with two heme proteins, hemoglobin (Hb) and myoglobin (Mb), has been studied employing various physicochemical and spectroscopic techniques like tensiometry, UV-Vis spectroscopy, steady-state fluorometry, time-resolved fluorometry, circular dichroism (CD) spectroscopy, calorimetry and stopped flow kinetics at physiological pH of 7.2 and 298K. Tensiometric and fluorometric analysis suggest that the interaction between SDDS and protein starts with the monomer form of the surfactant which produces small induced micelles. The micelles bind to protein backbone causing denaturation of the protein structure, and finally free micelles are formed on further addition of surfactant. Life-time measurements have been performed to shed light on the binding of surfactant around the tryptophan moieties present in the heme proteins. The changes in protein secondary structure induced by AAS collected from CD measurements reveals that the proteins are quite perturbed upon action of SDDS. The enthalpy change values of each stepwise interaction process have been found from isothermal titration calorimetry (ITC). The kinetics of the protein-surfactant interaction process has been studied using stopped flow technique. Quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis have been performed to highlight the interactive phenomenon between the surfactant and heme proteins. Thus the entire study shows a total inspection of an amino acid surfactant-heme protein interaction.