X-ray Absorption Spectroscopy of Selenium-Containing Amino Acids

Ingrid J. Pickering%, Graham N. George%, Verena Van Fleet-Stalder#, Thomas G. Chasteen#, and Roger C. Prince*

%Stanford Synchrontron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford, CA 94309, USA
#Department of Chemistry, Sam Houston State University, Huntsville, Texas, 77341-2117, USA
*Exxon research and Engineering Company, Annandale, NJ, 08801, USA

Journal of Biological Inorganic Chemistry, 1999, 4(6), 791-794. JIBC's abstract

Summary of work

Absorption spectra taken using K-edge X-ray analysis have been collected for selenomethionine, selenocysteine, selencystine, and sulfo-selenocystine in aqueous solutions of appropriate pH. The selenium K-edge spectra are similar to the sulfur K-edge spectra of the sulfur analogues of these molecules. The sulfur spectra, however, are sharper due to the longer core hole lifetime of sulfur.

The chemical (bonding) environment of selenium (and sulfur) in each of these molecules produces a change in the K-edge spectra due to a change in the energy of the transition. This takes the form of differences in absorption energy and peak widths discernible in the K-edge spectra. That said, comparison between structurally similar selenium and sulfur analogs is possible.

The result of this work suggests that these kinds of spectra can be used to determine the presence and amount of these kinds of Se-containing compounds in complex biological systems.

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