Phototherapy Drugs - Hypocrellin Prime Heme Class Of Protein Interaction Studies,

Hypocrellin A (HA), which was studied in this paper, is a potential phototherapeutic drug. In its photodynamic therapeutic procedure, it is injected intravenously into the patients. During this period, HA will react with many components of blood, and change their structures and properties. So it is important to study the interaction between HA and hemachrome protein and discuss the transport mechanism of HA in body for the development of hypocrellin apllication in the field of photodynamic therapy.The interaction between HA and some kinds of protein (such as lysozyme, myoglobin and hemoglobin) was studied by spectrophotometer, spectrofluorimeter and ESR spectrometer. It was found that the binding occured on the surface of protein through surface amino acid residues, and changed the conformation of protein, and had no direct effect on its interior structure. Their interaction forces are hydrophobic and electrostatic forces. Based on the experimental data, it was concluded that there are compounds forming between HA and protein, and all fluorescence quenchings are static with electron transfer. We can gain the binding constants and binding sites by dwelling with data, as well as the thermodynamic values and dynamic values during the formative process of the compound. The experiments show that there is no nonradiative energy transfer occurring between HA and the excited state of protein, it can be due to the small overlap between the fluorescence emission spectra of protein and the absorption spectra of HA.The results of Laser Raman spectroscopy indicated that active oxygen species (¹0₂, O₂^- and OH etc.) generated by HA can photodamage the structure of lysozyme. The orderly conformation (such as a-helix, p-sheet and P-turn) decreased obviously while the random coil increased. The indole ring, disulfide bond and carbon-sulfur bond in the side chain of lysozyme also decreased obviously. The change of the micro-environment of tryptophane residue and the carbon conformation of the disulfide chain in lysozyme shows that the conformation of the main chain changed.