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
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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