HpMTAN Enzyme (IMAGE) DOE/Oak Ridge National Laboratory Caption A nuclear density map of the bacterial enzyme HpMTAN's active site reveals the locations of the hydrogen atoms, including the unexpected observation of a hydrogen ion positioned midway between adenine and D198 residue. Credit ORNL 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.