title: Spectral studies of cobalt (II)- and Nickel (II)-metallothionein.
abstract: The zinc and cadmium of native rabbit metallothionein-1 were replaced stoichiometrically with either cobalt (II) or nickel (II). The electronic, magnetic circular dichroic (MCD), and electron spin resonance spectra of Co (II)-metallothionein reflect distorted tetrahedral coordination of the cobalt atoms. Both the d-d and charge-transfer spectral regions closely resemble those of simple cobalt-tetrathiolate complexes, implying that their coordination chemistry is analogous. Ni (II) complex ions and Ni (II)-metallothionein similarly exhibit analogous MCD bands in the d-d region. The circular dichroic bands associated with ligand-metal charge-transfer transitions in the non-d-d region of Co (II)- and Ni (II)-metallothionein afford additional evidence for the similarity in tetrahedral microsymmetry of the two metal derivatives. The known ratio of 20 thiolate ligands to 7 metal ions, in conjunction with the spectral evidence for tetrathiolate coordination in metallothionein, represents good evidence that these metal thiolates are organized in clusters.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002942:Circular Dichroism; D003035:Cobalt; D004578:Electron Spin Resonance Spectroscopy; D008099:Liver / Q000032:analysis; D008667:Metalloproteins; D008668:Metallothionein; D009532:Nickel; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D013053:Spectrophotometry
chemical_list: D008667:Metalloproteins; D003035:Cobalt; D009532:Nickel; D008668:Metallothionein