Spectroscopy (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption X-ray spectroscopy shows that a protein acetate group (molecule at center) prefers binding with sodium (blue curve) over potassium (red curve); the green sphere represents a cation, with surrounding water molecules in white. Credit Lawrence Berkeley National Laboratory, figure by Janel Uejio 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.