Figure 4.

Chemical shift index (CSI) plot of α-carbons of residues in the C-terminal tail of Fe³⁺-HO2^O. The values of CSI for β-strand, α-helix, and random coil are +1, −1, and 0, respectively, as defined by the program CSI.⁶⁵ Missing indices correspond to M262, which could not be assigned and the prolines (254, 266, and 283) for which assignments cannot be determined in the H-detect experiments. The assigned secondary structure illustrates the C-terminal region to be a random coil in Fe³⁺-HO2^O.