Electronic absorption spectra of M(II)(Met121X) azurins (MCo, Ni, Cu; XLeu, Gly, Asp, Glu): charge-transfer energies and reduction potentials

Abstract Electronic absorption spectra of the Co(II) and Ni(II) derivatives of Met121X (XLeu, Gly, Asp, Glu) azurin mutants have been measured. Coordination of carboxylate to the metal ion is indicated by LF and LMCT band shifts in the Met121Glu proteins. The relatively low reduction potentials of the Cu(II)(Met121X) (XAsp, Glu) azurins accord with the LMCT energies of the corresponding Co(II) derivatives.