Most ion channels are very selective about the ions that may or may not pass through them. They may be conductive for potassium ions and non-conductive for sodium ions, or vice versa. However, a number of ion channels allow for the efficient passage of both kinds of ions. How do these channel proteins accomplish this? A team of scientists around Dr. Han Sun and the research group of Professor Adam Lange at the Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP) found the answer to this question.