Circular Dichroism to Probe the Synthesis, Transfer, and Stability of Fe-S Clusters.

All Fe-S proteins are characterized by distinctive circular dichroism (CD) features in the visible region of the spectrum due to chiral interaction between the cluster itself and the protein backbone. Therefore, the presence of a CD signal in the visible region relates to the presence of the cluster, whereas the disappearance of the signal refers to cluster breakdown or redox changes. The position of the CD features in the spectrum and the intensity of individual components of the CD signal show great variations among different Fe-S proteins. This feature can provide information on transfer processes between proteins, as well as on possible changes in cluster nuclearity. This method can also be used to detect changes in the chemical nature or spatial organization of cluster ligands that may be concurrent with cluster transfer and associated events.