Figure 1 (IMAGE) Moscow Institute of Physics and Technology Caption Left: KR2 rhodopsin pentamer in its active state in the cell membrane (two horizontal disks). Right: sodium binding site in the active center of the protein. The distances to the oxygen atoms coordinating sodium are given in angstroms, or ten-billionths of a meter. The black grid is the electron density map. The violet sphere denotes a sodium ion. Credit Kirill Kovalev 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.