title: Photosensitized transformation of adrenochrome.
abstract: The methylene blue-sensitized photooxidation of adrenochrome was studied by steady-state kinetics. The buffered, aqueous system was irradiated with light longer than 600 nm, wavelengths at which only the sensitizer absorbs. During irradiation, disappearance of adrenochrome and the formation of adrenochrome-melanin was observed. Calculated rate constants were determined on the basis of spectroscopic measurements. It was found that the observed transformation reaction steps are pH dependent. The participation of two types of photosensitized mechanism has been evidenced. Type II, singlet oxygen mechanism, predominates at pH below 9, whereas above pH 9, Type I applies. We observed the so-called "isotope effect" and a decrease of photooxidation rate in the presence of azide ion, a well-known singlet oxygen quencher, indicating the participation of singlet oxygen.
authors.affiliation: Institute of Physics, Agricultural University, Poznan, Poland.
authors.forename: K
authors.initials: K
authors.lastname: Polewski
authors.forename: D
authors.initials: D
authors.lastname: Slawinska
mesh_terms: D000323:Adrenochrome / Q000737:chemistry* / Q000528:radiation effects; D001386:Azides / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008543:Melanins / Q000737:chemistry; D008751:Methylene Blue / Q000737:chemistry; D010084:Oxidation-Reduction; D010777:Photochemistry; D019810:Sodium Azide; D013482:Superoxide Dismutase; D014466:Ultraviolet Rays
chemical_list: D001386:Azides; D008543:Melanins; D000323:Adrenochrome; D019810:Sodium Azide; D013482:Superoxide Dismutase; D008751:Methylene Blue