Interaction between hemoglobin A and merocyanine 540: A spectroscopic investigation supported by docking

Merocyanine 540 (MC 540) is a clinically important dye and a potent sensitizer of lipid peroxidation in natural cell membrane like erythrocyte ghost. We have studied the binding interaction between this antileukemic drug and Hemoglobin A (HbA) using UV–visible absorption, steady-state, time-resolved fluorescence and circular dichroism spectroscopy. The changes in absorption spectra of HbA in presence of MC 540 suggest a ground state complex formation between them. Thermodynamic analyses of quenching of HbA with MC 540 at different temperatures imply that the interaction is spontaneous and H-bonding as well as van der Waals interactions play the key role in this particular interaction. The binding constant and stoichiometry of the complex are 2.89 × 104 M−1 and 1.0 respectively at 298 K. Circular dichroism and synchronous fluorescence spectra suggest a structural change in HbA in presence of MC 540. Theoretical docking study helps to find out the plausible binding site of MC 540 inside HbA.

► Interaction between human HbA and chemotherapeutic drug MC 540.
► MC 540 forms ground state complex with HbA.
► The binding stoichiometry between the interacting system is 1:1.
► MC 540 prefers hydrophobic cavity of HbA, observed from docking.