A new study unexpectedly identified tiny deposits of elemental copper and iron within the brains of two deceased people with Alzheimer's disease. The findings could help scientists better understand how these elemental metals, which were uncovered in the cores of amyloid plaques, contribute to neurodegenerative diseases and could point to a target for alternative Alzheimer's therapies. While enzymes and proteins containing positively charged copper and iron ions have been known to control key processes in the human brain, little has been known about how the organ mineralizes iron and copper, including the formation of elemental metallic nanoparticles, which are more reactive than the oxides from which they arise. To determine the distribution and chemical state of copper and iron within human amyloid plaque samples, James Everett and colleagues examined amyloid plaque cores taken from the gray matter of the frontal and temporal lobes of brains from two deceased Alzheimer's patients using synchrotron-based scanning transmission x-ray microscopy (STXM). Everett et al. identified iron and copper in different chemically reduced states within a single plaque, including various ionized as well as elemental forms, suggesting that repeated reduction and oxidation reactions may occur within these telltale clumps of misfolded proteins. "The unexpected identification of Cu0 and Fe0 within Alzheimer's disease amyloid plaques suggests that biogenic metallic elements, previously observed only in microorganisms, viruses, and plants, can also occur in humans," the authors write. "The reactivity of these metallic phases differs from their metal oxide counterparts previously detected in the human brain and has the scope to redefine our understanding of metal neurochemistry and the role of metal toxicity in neurodegenerative diseases."