Fig. 1.

1D ¹H NMR spectra of different Fe–S cluster types. 400 MHz 1D ¹H NMR spectra of Fe³⁺ (a) and Fe²⁺ (b) C. pasteurianum rubredoxin, acquired at 308 K (adapted from [13]); c 200 MHz 1D ¹H NMR spectrum of [2Fe–2S]²⁺ P. umbilicalis ferredoxin, acquired at 303 K [15]; d 360 MHz 1D ¹H NMR spectrum of [2Fe–2S]⁺ P. umbilicalis ferredoxin, recorded at 303 K [25]; e 400 MHz 1D ¹H NMR spectrum of [2Fe–2S]⁺ human ferredoxin, acquired at 303 K [201]; f 500 MHz 1D ¹H NMR spectrum of [3Fe–4S]⁺ P. furiosus ferredoxin, recorded at 303 K [33]; 600 MHz 1D ¹H NMR spectra of [4Fe–4S]²⁺, g [40] and [4Fe–4S]³⁺, i [60] E. halophila HIPIP II, recorded at 300 K; h 600 MHz 1D ¹H NMR spectrum of [4Fe–4S]⁺ C. acidi urici ferredoxin, acquired at 298 K [43]