| Abstract | Zinc is the most common trace element and is the only transition metal known to be required for at least one enzyme in each of the major classes of enzymatic activities. Unfortunately, characterization of Zn(II) in biological systems is challenging. Zinc is found only in the Zn(II) oxidation state, and thus, as a d10 ion, is “silent” to most traditional spectroscopies. This makes the characterization of Zn sites extremely difficult in the absence of a crystal structure. X-ray spectroscopy, including extended x-ray absorption fine structure (EXAFS) x-ray absorption near edge structure (XANES), and x-ray emission spectroscopy (XES) is the principal exception to this generalization, and both EXAFS and XANES have found frequent application in the characterization of biological Zn sites, and more recently high-resolution XES, has been shown to provide complementary information. The applications of these to methods to the characterization of the nucleophilic Zn site in a novel class of Zn methyl-transfer enzymes will be described. |
