A comparative spectroscopic and calorimetric investigation of the interaction of amsacrine with heme proteins, hemoglobin and myoglobin

The binding affinity to hemoglobin was (1.21 ± .05) × 10 5 M −1 , while that to myoglobin was three times higher (3.59 ± .15) × 10 5 M −1 . The temperature-dependent fluorescence study confirmed the formation of ground-state complexes with both the proteins.

The stronger binding to myoglobin was confirmed from both spectroscopic and calorimetric studies. The binding was exothermic in both cases at the three temperatures studied, and was favored by both enthalpy and entropy changes. Circular dichroism results, three-dimensional (3D) and synchronous fluorescence studies confirmed that the binding of amsacrine significantly changed the secondary structure of hemoglobin, while the change in the secondary structure of myoglobin was much less.