期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 44, 页码 18783-18786出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1012381107
关键词
ruthenium bipyridine; enzyme catalysis
资金
- National Institutes of Health [DK019038]
- Arnold and Mabel Beckman Foundation
High-valent iron-oxo species are thought to be intermediates in the catalytic cycles of oxygenases and peroxidases. An attractive route to these iron-oxo intermediates involves laser flash-quench oxidation of ferric hemes, as demonstrated by our work on the ferryl (compound II) and ferryl porphyrin radical cation (compound I) intermediates of horseradish peroxidase. Extension of this work to include cytochrome P450-BM3 (CYP102A1) has required covalent attachment of a Ru(II) photosensitizer to a nonnative cysteine near the heme (Ru(K97C)(II)-Fe(P450)(III)), in order to promote electron transfer from the Fe(III) porphyrin to photogenerated Ru(III). The Ru(K97C)(II)-Fe(P450)(III) conjugate was structurally characterized by X-ray crystallography (2.4 angstrom resolution; Ru-Fe distance, 24 angstrom). Flash-quench oxidation of the ferric-aquo heme produces an Fe(IV)-hydroxide species (compound II) within 2 ms. Difference spectra for three singly oxidized P450-BM3 intermediates were obtained from kinetics modeling of the transient absorption data in combination with generalized singular value decomposition analysis and multiexponential fitting.
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