Fig. 1.

a The chemical structure of amotosalen. b The mechanism of action. The INTERCEPT Blood System for platelets and plasma uses a combination of amotosalen (structure as shown) and long wavelength ultraviolet A (UVA) light. The amotosalen compound penetrates cellular and nuclear membranes and intercalates into the helical regions of DNA and RNA. Covalent crosslinks to the nucleic acid base pairs form upon exposure to UVA light (reactive groups highlighted in yellow), blocking DNA and RNA replication.