ABSTRACT
In nature, metalloenzymes are able to carry out remarkable chemical transformations with a selectivity and efciency that is often difcult or even impossible to mimic in the laboratory. Driven by a desire to use nature as an inspiration for rational catalysis design, the eld of bioinorganic chemistry has had a long history of trying to understand the mechanism of metalloenzyme mediated chemical transformations. This means that one wants to understand how the metalloenzyme, in particular, the metal “active site” changes before, during, and after the chemical reaction. It is here that X-ray spectroscopy has played a pivotal role. Some of the earliest insights into
5.1 Introduction .................................................................................................. 153 5.2 Methods ........................................................................................................ 154 5.3 Applications of Kβ XES ............................................................................... 156 5.4 Applications of V2C XES............................................................................. 157
5.4.1 Applications of V2C XES Relevant to Photosystem II .................... 157 5.4.2 Applications of V2C XES Relevant to Nitrogenase ......................... 159 5.4.3 Applications of V2C XES Relevant to Hydrogenase........................ 160 5.4.4 Applications of V2C XES to Galactose Oxidase ............................. 160 5.4.5 Insight into V2C XES from Small Molecule Studies ....................... 161
5.5 Applications of RXES .................................................................................. 162 5.5.1 Applications of RXES to Photosystem II and Related Models ........ 162 5.5.2 Applications of RXES to Hydrogenase ............................................ 163 5.5.3 Applications of Kβ-Detected XANES ............................................. 163
5.6 Applications of Dispersive XES ................................................................... 163 5.7 Summary and Outlook ................................................................................. 164 References .............................................................................................................. 164
the active site structures of metalloproteins came from early X-ray absorption spectroscopy studies (XAS), particularly in the extended X-ray absorption ne structure region (EXAFS). These studies provided some of the rst hints of the complexity of the active site in nitrogenase (which is responsible for the reduction of N2 to NH3), as well as providing the rst measure of Mn-Mn distances within the oxygen-evolving complex of Photosystem II.1,2 In addition, EXAFS studies have provided insight into numerous enzymatic intermediates-including the active sites of laccase,3 ribonucleotide reductase,4 and methane monooxygenase,5 to name only a few.
