Proteins interactions with reactive oxygen agents may result in covalent modifications of amino acid residues in proteins, formation of protein-protein cross-linkages and oxidation of the protein backbone resulting in protein fragmentation. Oxidation targets for Aß(1-16) are the histidine residues coordinated to the metal ions. Copper is bound to Aß in senile plaque of Alzheimer’s disease with Aß (1-16) taking part in the coordination of the Cu2+ ions. Cu2+ and Zn2+ are linked with the neurotoxicity of Aß and free radical damage.