6-Molecule Ring of Urea Channels (image) DOE/SLAC National Accelerator Laboratory Caption An isolated look at the structure of the six-molecule ring of urea channels embedded in the membrane of Helicobacter pylori. Urea passes through the center of each of the six channel molecules. The center of the ring is filled with a lipid bilayer plug. Credit Hartmut Luecke / UC Irvine Usage Restrictions Provide credit. 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.