Reaction Stages of Psoralen with DNA (IMAGE) Heinrich-Heine University Duesseldorf Caption Reaction stages when a psoralen molecule binds to DNA. The result is that the psoralen is permanently bound to the DNA via a cyclobutane ring. The cell is altered and thus damaged, and triggers the process of programmed cell death. Credit ACS / Janina Diekmann 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.