title: Clue to Understanding the Janus Behavior of Eumelanin: Investigating the Relationship between Hierarchical Assembly Structure of Eumelanin and Its Photophysical Properties.
abstract: The contradictory biological function of eumelanin (photoprotection vs photosensitization) has long been a topic of debate in a wide range of disciplines such as chemistry, physics and biology. For understanding full spectrum of eumelanin's photobiological aspect, revealing how eumelanin's complex structural organization dictates its photophysical properties is critical step. Here, we report a practical approach to controlling the hierarchically assembled structure of natural eumelanin, which leads to disassembly of its structure into subunits and oxidized subunits, respectively. Based on the well-characterized model system, it was possible to systematically determine how the photophysical properties of eumelanin are ruled by its hierarchical assembly organization. Particularly, our experiments reveal that the chemical oxidation of eumelanin's subunits, which leads to delamination of their stacked layer structure, is critical to significantly increase their photochemical reactivity to generate ROS under UV irradiation. This result provides clear experimental evidence that oxidative degradation of eumelanin, which might be induced by phagosomal enzymatic activity in the process of melanomagenesis, is responsible for triggering the negative photobiological role of eumelanin such as ROS source needed for development of malignant melanoma.
authors.affiliation: Department of Chemistry, Seoul National University , Seoul 151-747, Korea.
authors.forename: Kuk-Youn
authors.initials: KY
authors.lastname: Ju
authors.affiliation: Department of Electronics Engineering and Sogang Institute of Advanced Technology, Sogang University , Seoul, 121-742, Korea.
authors.forename: Jeeun
authors.initials: J
authors.lastname: Kang
authors.affiliation: Department of Electronics Engineering and Sogang Institute of Advanced Technology, Sogang University , Seoul, 121-742, Korea.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Chang
authors.affiliation: Department of Chemistry, Seoul National University , Seoul 151-747, Korea.
authors.forename: Jin-Kyu
authors.initials: JK
authors.lastname: Lee
mesh_terms: D000818:Animals; D001703:Biophysics; D008543:Melanins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D055095:Optics and Photonics; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D049833:Sepia / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D008543:Melanins; D017382:Reactive Oxygen Species; C041877:eumelanin