Superoxo, μ-Peroxo, and μ-Oxo Complexes from Heme/O2 and Heme-Cu/O2 Reactivity: Copper Ligand Influences in Cytochrome c Oxidase Models

• Published in: Proceedings of the National Academy of Sciences - PNAS 2003-04, Vol.100 (7), p.3623-3628
• Main Authors: Kim, Eunsuk, Helton, Matthew E., Wasser, Ian M., Karlin, Kenneth D., Lu, Shen, Huang, Hong-wei, Moënne-Loccoz, Pierre, Incarvito, Christopher D., Rheingold, Arnold L., Honecker, Marcus, Kaderli, Susan, Zuberbühler, Andreas D.
• Format: Article
• Language: English
• Subjects: Biochemistry; Bioinorganic Chemistry Special Feature; Blood; Copper; Cytochromes; Electron Transport Complex IV - chemistry; Electron Transport Complex IV - metabolism; Heme - metabolism; Kinetics; Ligands; Models, Molecular; Oxidases; Oxygen - metabolism; Physical Sciences; Protein Binding; Protein Conformation; Solvents; Spectroscopy; Tissue oxygenation; Vibration
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0737180100

The O2-reaction chemistry of 1:1 mixtures of $(F_8)Fe^{II}\>(1;\>F_8 = tetrakis(2, \!6\!-\!diflurorophenyl)porphyrinate)$ and $\lbrack(L^{Me_2N})Cu^I\rbrack^+\>(2;\>L^{Me_2N} = N, \!N\!-\!bis\lbrace2\!-\!\lbrack2\!-\!(N^\prime, \!N^\prime\!-\!4\!-\!dimethylamino)pyridyl\rbrack ethyl\rbrace methylamine)$ is described, to model aspects of the chemistry occurring in cytochrome c oxidase. Spectroscopic investigations, along with stopped-flow kinetics, reveal that low-temperature oxygenation of 1/2 leads to rapid formation of a heme-superoxo species (F8)FeIII-(O2-) (3), whether or not 2 is present. Complex 3 subsequently reacts with 2 to form [(F8)FeIII-(O22-) -CuII(LMe2N)]+ (4), which thermally converts to [(F8)FeIII-(O)- CuII(LMe2N)]+ (5), which has an unusually bent (Fe-O-Cu) bond moiety. Tridentate chelation, compared with tetradentate, is shown to dramatically lower the ν(O-O) values observed in 4 and give rise to the novel structural features in 5.