Iodide Binding Sites (IMAGE) Moscow Institute of Physics and Technology Caption Iodide binding sites in various protein structures. Panels A, B, C, and D show different protein structures with traces of iodide ions depicted in purple (on the left). The same structures are shown embedded in the cell membrane (right). The image illustrates the tendency of iodide ions (orange spheres) to attach to proteins at the outer (blue) or inner (red) surface of the membrane, where positive charge is concentrated. Credit The study under discussion published in Science Advances 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.