X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfur and chlorine centers in photographic materials
The dinuclear iron center of the hydroxylase component of soluble methane monooxygenase (MMO) from Methylococcus capsulatus (Bath) and Methylosinus trichosporium (OB3b) has been studied by X-ray absorption spectroscopy. Analysis of the Fe K-edge EXAFS revealed that the first shell coordination of the hydroxylase consists of [approximately]6 N and O atoms at an average distance of 2.04[angstrom] in the oxidized form, increasing to 2.06-2.09[angstrom] in the semimet form, and 2.15 [angstrom] for the oxidized and semimet hydroxylase samples. No evidence for the presence of a short oxo bridge in the iron center was found. The presence of component B, the regulatory protein of the MMO enzyme system, had an effect on the distance distribution of first shell atoms in the hydroyxlase active site. No evidence of a Br contribution was seen in the hydroxylase EXAFS in the presence of a brominated substrate, suggesting the substrate binds more than 4[angstrom] from the iron center. An investigation of the EXAFS analysis technique using structurally-characterized iron dimers demonstrated that the results of the second shell fits exhibit a bias for the Fe-FE distance of the model compound from which the fitting parameters were obtained. An asymmetric pre-edge feature in the edge spectra of iron dimers was characteristic of oxo-bridge compounds, while a split pre-edge was characteristic of non-oxo-bridged compounds. Spectral sensitizing dyes and chemical sensitizing centers of importance to the photographic system were characterized by S and Cl K-edge X-ray absorption spectroscopy. The appearance of the S K-edge spectra was characteristic of the environment of the S atoms and oriented single-crystal studies permitted the assignment of the features. The nature and extend of interaction between S and Ag and Au was characterized using XAS and used to investigate the nature of the interaction between photographic dyes and the AgBr substrate.
- Research Organization:
- Stanford Univ., CA (United States)
- OSTI ID:
- 7207448
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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X-ray absorption spectroscopic studies of the dinuclear iron center in methane monooxygenase and the sulfure and chlorine centers in photographic materials
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Related Subjects
OXYGENASES
X-RAY SPECTRA
PHOTOGRAPHIC EMULSIONS
CHLORINE COMPLEXES
IRON COMPLEXES
K ABSORPTION
METHANOTROPHIC BACTERIA
STRUCTURAL CHEMICAL ANALYSIS
SULFUR COMPLEXES
ABSORPTION
BACTERIA
COLLOIDS
COMPLEXES
DISPERSIONS
EMULSIONS
ENZYMES
MICROORGANISMS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
PROTEINS
SORPTION
SPECTRA
TRANSITION ELEMENT COMPLEXES
360602* - Other Materials- Structure & Phase Studies