This thesis aims to examine the interaction of transition metal ions with histidine-containing dipeptides in order to understand how these ions coordinate in metalloenzymes. With a group of researchers from the University of Debrecen we investigate the Tau Protein which is the main component of the intracellular filamentous inclusions that are linked with neurodegenerative diseases. Series of potentiometric and spectroscopic experiments were performed to study the interactions between nickel(II) ions and methionyl-histidine (Met-His) dipeptide in Tau(26-33) – TMHsequence). While the potentiometric experiments will provide information about the thermodynamics of metal-peptide binding, the spectroscopic analysis have yielded useful insights into the coordination geometry and structural data of the formed complexes.