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| James Penner-Hahn - | |
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Over the last thirty years, x-ray absorption spectroscopy (XAS) has emerged
as one of the premier techniques for investigating the structure and
function of metal ions in metalloproteins. XAS has proven particularly
useful for studies of the biological function of zinc, an element that is
not accessible to conventional spectroscopic methods. With the development
of third generation synchrotron sources, the scope of x-ray spectroscopy
has significantly broadened. In part, these new capabilities result from
the higher flux of the third generation sources. Examples of how the
ability to make measurements ?faster, smaller, and better? has expanded
the scope of x-ray spectroscopy will be discussed, with particular emphasis
on understanding the mechanism of zinc-promoted alkyl transfer enzymes.
In addition, two new classes of experiments have become possible with the
development of third generation sources: Microprobe spectroscopy and
high-resolution x-ray emissions spectroscopy (XES). Microprobe spectroscopy
can be used to interrogate directly the structure and function of metal ions
in intact biological samples. Examples of how this can be used to understand
the role of zinc in brain function will be discussed. Finally, the very high
brightness of third generation source allows extremely improbable XES
features events to be studied in a practical period of time. The latter
capability has allowed, for the first time, the use of x-ray spectroscopy
to distinguish between nitrogenic, hydroxo, and aquo ligands. Examples of
how this has been used to characterize the role played by zinc in the enzyme
carbonic anhydrase will be discussed.
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