title: Thiyl free radical production with hematoporphyrin derivative, cysteine and light: a spin-trapping study.
abstract: Hematoporphyrin derivative, used in photodynamic therapy of cancer, was found to generate the cysteinyl free radical as seen by spin-trapping. Oxygen appears to be an absolute requirement for thiyl radical production. Singlet oxygen may be the initiating species since azide inhibits oxygen uptake and radical production. In addition, the hydroxyl radical, or a radical with similar reactivity, is also observed and is proposed as the precursor for thiyl free radical production.
mesh_terms: D003545:Cysteine; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins; D008027:Light; D010777:Photochemistry; D011838:Radiation-Sensitizing Agents; D013455:Sulfur
chemical_list: D005609:Free Radicals; D006415:Hematoporphyrins; D011838:Radiation-Sensitizing Agents; D017324:Hematoporphyrin Derivative; D013455:Sulfur; D003545:Cysteine