Aloys (Al) Tappel, professor emeritus of food science and technology at UC Davis, is an expert on oxidative damage and antioxidants. Some forms of oxygen, called free radicals, are highly reactive in the body and can cause damage to cells and proteins. Oxygen radicals appear to be involved in a range of diseases including heart disease and Alzheimer's disease and also are used by the body's immune system to protect against parasites. Diets high in antioxidants are associated with lower rates of some diseases, although demonstrating a direct protective effect of antioxidant treatment has proven difficult. In the 1960s, Tappel's laboratory made some of the first observations of how reactive oxygen can damage proteins by causing a reaction that sticks proteins and other biomolecules into a chain. Tappel thinks that similar processes may be an important factor in Alzheimer's disease, leading to the formation of amyloid plaques and tangles.