When most people hear the word amyloid, they immediately think of Alzheimer’s disease. And indeed, it was in the brains of Alzheimer’s patients that these dense protein masses were first identified. But it turns out that besides playing a role in a number of diseases, amyloids also play an important structural role in many organisms from bacteria to mammals, and might point the way to a whole new category of biologically inspired synthetic materials.
Each protein normally folds itself into a specific shape that governs many aspects of its interactions with other materials and organisms. But almost all proteins and peptides (organic molecules that are similar to proteins but shorter) can alternatively form amyloids, which all have the same essential structure but form dense, concentrated masses instead of precisely folded shapes. These densely packed cores consist of stacks of molecular structures called beta sheets, tightly bound together by hydrogen bonds; a single “seed” of amyloid can induce many of the nearby proteins to collapse into similar amyloid structures.
A close-up view of an amyloid plaque model, showing the entangled structure of amyloid fibrils that form a sticky plaque.
Image: M. Solar, MIT