Photooxidation is observed in many biological systems following excitation with ultraviolet (UV) light. Even though it is a driving force for numerous important photochemical reactions, for example in photocycles of fl uorescent proteins, it can also have deleterious effects, such as in photodamage of DNA. We will present the results of femtosecond transient absorption spectroscopy experiments, complemented by liquid-microjet photoelectron spectroscopy measurements and quantum chemistry calculations, that probe the photochemical dynamics of UV photooxidation in biochromophores.