Luminescence emission from the Cu(I)-thiolate complex in metallothioneins

The luminescence emission properties of Cu-metallothioneins (from Neurospora crassa, Agaricus bisporus and livers of Bedlington terriers affected by copper toxicosis) as well as of (Cu,Zn)-metallothionein from bovine fetal liver are reported. Upon excitation in the U.V., these proteins emit a largely red-shifted luminescence with a maximum at 565 nm attributable to the Cu(I)-thiolate chromophores of the proteins. Differences in the shapes of the spectra and the emission intensity are observed with (Cu,Zn)-metallothionein probably due to the influence of Zn ions or to a different coordination geometry of the Cu ions. The emissive properties of the Cu(I)-thiolate chromophore are compared with those of metallo-organic Cu(I)-mercaptide complexes.