“…Paramagnetic NMR investigations on cupredoxins include studies of the native Cu(II) species [19,20,21,22,23] and of their Co(II) and Ni(II) derivatives [15,24,25,26,27,28,29,30,31,32,33,34,35,36,37]. These studies have afforded evidence on the interplay between the strength of the metal-axial ligand interaction and the metal-Cys covalence [15,20,21].…”