Characterization of interactions between cromolyn sodium and bovine serum albumin by spectroscopic, calorimetric and computational methods.

Cromolyn sodium, an anti-inflammatory drug is used in the treatment of allergic disorders. Bovine serum albumin (BSA) a blood plasma protein is used as a model protein for studying protein folding and ligand binding mechanism as it is the main transporter protein which decides the disposition and pharmacodynamics of numerous drugs. In this study, interaction of cromolyn sodium with bovine serum albumin was investigated using isothermal titration calorimetry, UV-vis, fluorescence, circular dichroism spectroscopy and molecular docking tecniques. Steady state fluorescence data revealed that BSA-cromolyn sodium complex formation occurred through static mode of quenching. Negative values of Gibbs free energy change and enthalpy change showed that BSA-cromolyn sodium complexation was spontaneously favorable and enthalpy driven. Cromolyn sodium preferentially interacted at Sudlow's site I (sub-domain IIA) of BSA and the finding was further substantiated by molecular docking study. The binding of cromolyn sodium induced changes in secondary motif of BSA resulting decrease of α-helical content as evident from circular dichroism. We explored detailed thermodynamic and structural parameters of interaction of cromolyn sodium to BSA that will be helpful for understanding the more precise binding mechanism of the drug at molecular level.