Fig. 3 (IMAGE) Osaka University Caption Protonation state of copper-coordinated histidine residues. One of the histidine residues is fully deprotonated as shown in a red circle to form an unusual imidazolate anion. Credit Osaka University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.