Iron-sulfur Custer Molecule (IMAGE) Virginia Tech Caption Depicted is a molecular representation of a four iron- four sulfur cluster in which the sulfur is shown in yellow and iron in green. Credit Callie Raulfs Usage Restrictions With news of the research on iron-sulfur clusters by Virginia Tech researchers, as reported in PNAS. 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.