Analysis of X-ray absorption edge spectra can provide insight into the electronic structure of  protein active sites. The pre-edge of S K-edge can provide important information like Fe-S bond covalency and oxidation state of Fe in Fe-S cluster containing proteins or model complexes. My projects involve using S K-edge XAS spectra and DFT calculations to understand the electronic structure of Fe-S cluster in various proteins and model complexes, and how the environment tunes the electronic structure of Fe-S cluster.