Spectral decomposition of iron-sulfur clusters

The near universal availability of UV–Visible spectrophotometers makes this instrument a highly exploited tool for the inexpensive, rapid examination of iron-sulfur clusters. Yet, the analysis of iron-sulfur cluster reconstitution experiments by UV–Vis spectroscopy is notoriously difficult due to the presence of broad, ill-defined peaks. Other types of spectroscopies, such as electron paramagnetic resonance spectroscopy and Mössbauer spectroscopy, are superior in characterizing the type of cluster present and their associated electronic transitions but require expensive, less readily available equipment. Here, we describe a tool that utilizes the accessible and convenient platform of Microsoft Excel to allow for the semi-quantitative analysis of iron-sulfur clusters by UV–Vis spectroscopy. This tool, which we call Fit-FeS, could potentially be used to additionally decompose spectra of solutions containing chromophores other than iron-sulfur clusters.