Interaction of antiviral and antitumor photoactive drug hypocrellin A with human serum albumin.

Abstract Absorption, resonance Raman, surface-enhanced Raman spectroscopy and differential scanning microcalorimetry were employed to study the interaction of hypocrellin A with human serum albumin. The identification of the binding place for hypocrellin A as well as the model for the albumin-hypocrellin A complex are proposed. In this model hypocrellin A interacts with albumin through more than one binding site placed on the protein surface. This model of non-specific interaction could explain why the absorption spectrum of hypocrellin A does not change in the presence of albumin and why the presence of the drug does not change significantly the thermodynamic parameters of the protein, while the Raman spectra show evident changes concerning both the protein and the drug structure. Even if hypocrellin A does not interact with an interior binding site, it can affect deeply the general albumin structure.