XAFS study of the configuration of l-histidine with Mn2+, Co2+, Ni2+, Cu2+, Zn2+ at pH 6.0

Divalent transition metal ions have a strong relationship with l-histidine (His) in many important biological processes. In this work, the solution complexes of His and Mn2+, Co2+, Ni2+, Cu2+, Zn2+ with a molar ratio 2:1 separately at pH 6.0 were studied by extended X-ray absorption fine structure (EXAFS). The result supports that all the Metal/His complexes have distorted octahedral geometries, but the configurations of Cu/His and Zn/His are more disordered than that of Mn/His, Co/His and Ni/His. Data also indicate that the bond distances between the metals ions and histidine ligands present a clear trend consistent with the rule of the Irving–Williams series.