Spectroscopic studies on the interaction of hypocrellin A with myoglobin

Experimental results of UV-visible absorption spectroscopy and fluorescence spectroscopy indicate that hypocrellin A, which has been studied in photodynamic therapy, can interact with the surface of myoglobin through hydrophobic forces, and form a complex. Based on the Stern–Volmer equation, the quenching constants of the process can be calculated to be 4.81×1012 L mol？1 s？1 (t=25°C) and 4.54×1012 L mol？1 s？1 (t=42°C) respectively, and the binding constant is 5.53×104 M？1 (t=25°C), while the binding sites is 0.94 (t=25°C). In addition, Electron paramagnetic resonance and fluorescence spectroscopic analysis suggests that that the quenching mechanism of the interaction process occurs through the electron transfer between hypocrellin A and myoglobin.