Reaction Stages of Psoralen with DNA (image) Heinrich-Heine University Duesseldorf Share Print E-Mail 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 Share Print E-Mail 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.