Protein misfolding is considered to be a primary cause of Alzheimer’s Disease, whereby in a multistep process, proteins misfold and accumulate into large extra- or intracellular aggregates – that may be precursors to toxic mature plaques.  Jan Bieschke, from the Max Delbrueck Center for Molecular Medicine (Germany), and colleagues have isolated a red dye derived from lichens that has been used for centuries to color fabrics and food.  The team found that the dye – a compound called orcein, and a related substance – known as O4, bind preferentially to small amyloid aggregates that are considered to be toxic and cause neuronal dysfunction and memory impairment in Alzheimer’s disease. The study authors report that: “These results support the hypothesis that small, diffusible prefibrillar amyloid species rather than mature fibrillar aggregates are toxic for mammalian cells.”