The goal of this project is to strengthen the ability of x-ray absorption spectroscopy to characterize complex mixtures often found in biological samples. X-ray fluorescence is sensitive to the chemical state of an atom. Thus, x-ray absorption spectra from chemically distinct sites in a complex sample can be obtained by monitoring the x-ray fluorescence signal with high energy resolution. Progress in x-ray spectrographs, detectors, and sources now allows this experiment to be applied to dilute materials such as metals in enzymes. Construction of an x-ray spectrograph using spherically bent crystals and a high spatial resolution detector is proposed. The fluorescence spectra of model compounds for elements from sulfur through molybdenum will be investigated. From these emission spectra the best energies for """"""""site-specific x-ray absorption spectroscopy"""""""" will be determined. This technology will be applied to differentiate Mn(II,III,IV) environments in catalase and photosystem II, Cu(I,II) sites in mixed-valence cytochrome oxidase, and Fe(ll,III) species in binuclear iron oxygenases, and eventually to catalytic intermediates. K-edge absorption spectra recorded with high resolution fluorescence detection can show features sharper than the natural line width. This advantage will be used to characterize the S, V, Fe and Mo sites of nitrogenase. The instrumentation and methods developed during this project should be generally applicable to characterization of trace elements in biology.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM048145-01
Application #
3307610
Study Section
Metallobiochemistry Study Section (BMT)
Project Start
1992-08-01
Project End
1995-07-31
Budget Start
1992-08-01
Budget End
1993-07-31
Support Year
1
Fiscal Year
1992
Total Cost
Indirect Cost
Name
University of California Davis
Department
Type
Schools of Engineering
DUNS #
094878337
City
Davis
State
CA
Country
United States
Zip Code
95618