Lysozyme dimer formation on lysozyme oxidation with Br2 radical as studied by fluorescence evolution.
Lysozyme dimers produced on oxidation of lysozyme with Br2 radical in aqueous solutions exhibit a fluorescence spectrum (lambda max = 400 nm) closely similar to that of bi-tyrosine. This suggests that the dimer is likely to have a tyrosine-tyrosine bond resulting from the combination of tyrosine phenoxy radicals of two lysozyme molecules. Kinetic studies on dimer formation were made by measuring time-dependent fluorescence after pulsed-electron irradiation over wide pH range. The results lead to the following conclusions. The second-order growth of the dimer fluorescence observed at pH 10.7-12.5 reflects the combination process of the lysozyme radicals, which is rate-determining in the pH range. On the other hand, the first-order growth observed at pH 6.8-10.2 is attributable to the enolization of the keto-form of the dimer. A tentative reaction scheme is proposed for the dimer formation.
D001965:Bromides / Q000528:radiation effects; D004583:Electrons; D005720:Gamma Rays; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000528:radiation effects*; D010084:Oxidation-Reduction; D012964:Sodium / Q000528:radiation effects; D017670:Sodium Compounds; D012996:Solutions; D013050:Spectrometry, Fluorescence; D014867:Water
D001965:Bromides; D017670:Sodium Compounds; D012996:Solutions; D014867:Water; D012964:Sodium; D009113:Muramidase; C027938:sodium bromide