Sunburn in living organisms is caused by ultraviolet (UV) light from the sun damaging the DNA in the cells. Many organisms, however, have an in-built mechanism for repairing the sun damage. This is possible thanks to an enzyme called DNA photolyase, which is so specialised that cryptochrome, a structurally similar molecule, is unable to do the same job. By comparing both types of molecule, physicists can understand precisely how the ability of our enzymes to repair DNA boils down to the most minute structural details. In a study published in The European Physical Journal D, Katrine Aalbæk Jepsen from the University of Southern Denmark, in Odense, and her colleague Ilia Solov’yov pinpoint the mechanism by which repair enzymes bind to the damaged site.