title: Peroxide decoloration of CI Acid Orange 7 catalyzed by manganese chlorophyll derivatives at the surfaces of micelles and lipid bilayers.
abstract: Manganese-substituted chlorophyll a derivatives (MnChls) were synthesized. We first report peroxidative oxidation of an azo dye, CI Acid Orange 7, catalyzed by MnChls at the surfaces of micelles and lipid bilayers with hydrogen peroxide (H(2)O(2)) under mild conditions (pH 8.0, 25 degrees C). Peroxide decoloration depended upon the structures of MnChls, surfactants, lipids, and the presence of imidazole. Surprisingly, a largest decoloration rate was observed for MnChls dimer, MnPChlide a-K(MnPChlide a)-His 5 in cetyltrimethylammonium bromide (CTAB) micellar solution, especially when imidazole was present: this observation is analogous to the decoloration using horseradish peroxidase (HRP). Interestingly, the dimer complexes showed enhanced decoloration in comparison to the corresponding MnChls monomer in the micellar solution. In contrast, the MnChls monomer showed enhanced decoloration in comparison with the MnChls dimer in liposomal suspensions. Further, the imidazole residue covalently linked to the MnChls plays an important role in increasing the decoloration in both micellar and liposomal suspensions as well as in addition of imidazole into the solutions. It is interesting that the electron paramagnetic resonance (EPR) spectra of MnPChlide a ME 2, MnPChlide a-His 3, and MnMPMME-His 7 have 16 peaks around g = 2 in Egg PC or DMPC liposomal suspension with H(2)O(2), which is typical of a mixed-valence Mn(III)-Mn(IV) complex with coupling between two ions. The higher decoloration performance obtained by the monomer porphyrin compounds at the surface of the lipid bilayers appears to be related to the stability of this mixed-valence Mn(III)-Mn(IV) species formed in the lipid bilayers. This finding should provide useful information to note that MnChls, which are easily found in a number of biological systems, are involved in functions such as hydrogen peroxide decomposition in bacteria and the oxidation of water during photosynthesis as well as the peroxidases function such as the peroxidative decoloration as bleaching agents.
authors.affiliation: Department of Life and Materials Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ishigure
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Mitsui
authors.forename: Shingo
authors.initials: S
authors.lastname: Ito
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kondo
authors.forename: Shigeki
authors.initials: S
authors.lastname: Kawabe
authors.forename: Masaharu
authors.initials: M
authors.lastname: Kondo
authors.forename: Takehisa
authors.initials: T
authors.lastname: Dewa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Mino
authors.forename: Shigeru
authors.initials: S
authors.lastname: Itoh
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nango
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D001557:Benzenesulfonates / Q000737:chemistry*; D002384:Catalysis; D000077286:Cetrimonium; D002593:Cetrimonium Compounds; D002734:Chlorophyll / Q000737:chemistry*; D003116:Color; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers; D008345:Manganese / Q000737:chemistry*; D008823:Micelles; D010545:Peroxides / Q000737:chemistry*; D013501:Surface-Active Agents
chemical_list: D001391:Azo Compounds; D001557:Benzenesulfonates; D002593:Cetrimonium Compounds; D008051:Lipid Bilayers; D008823:Micelles; D010545:Peroxides; D013501:Surface-Active Agents; D002734:Chlorophyll; D008345:Manganese; C014722:2-naphthol orange; D000077286:Cetrimonium