Characterization of the binding of strychnine with bovine -lactoglobulin and human lysozyme using spectroscopic, kinetic and molecular docking analysis

The binding interaction of a well known alkaloid strychnine (STN) with the mammalian milk protein -lactoglobulin and human lysozyme has been explored by using several spectroscopic techniques along with computational studies. Steady-state and time-resolved fluorescence spectral data reveal that quenching of protein fluorescence proceeds through ground state complexation, i.e., a static quenching mechanism. However, the drug-protein binding constant has been found to vary proportionately with temperature. This anomalous result is explained on the basis of Arrhenius theory. Thermodynamic parameters have been estimated from temperature dependent fluorometric analysis in conjunction with isothermal titration calorimetric (ITC) study. Moreover, modification of native protein conformation due to drug binding has been investigated by UV-Vis spectroscopy, NMR spectroscopy and circular dichroism (CD) measurements. Drug-protein association kinetics has been studied using stopped flow kinetics. Furthermore, molecular dynamics study has provided accurate insights into the binding of STN with both the proteins in accordance with the experimental results obtained. Overall, our present studies report the moderately strong binding affinity of the alkaloid with bovine -lactoglobulin and human lysozyme, which would be helpful for the medical and environmental sciences.