Abstract
Amyloid fibrils are deposited in a number of diseases, including Alzheimer's disease, Type 2 diabetes, and the transmissible spongiform encephalopathies (TSE). These insoluble deposits are formed from normally soluble proteins that assemble to form fibrous aggregates that accumulate in the tissues. Electron microscopy has been used as a tool to examine the structure and morphology of these aggregates from ex vivo materials, but predominantly from synthetic amyloid fibrils assembled from proteins or peptides in vitro. Electron microscopy has shown that the fibrils are straight, unbranching, and are of a similar diameter (60β100 Γ
) irrespective of the precursor protein. Image processing has enhanced electron micrographs to show that amyloid fibrils appear to be composed of protofilaments wound around one another. In combination with other techniques, including Xβray fiber diffraction and solid state NMR, electron microscopy has revealed that the internal structure of the amyloid fibril is a ladder of Ξ²βsheet structure arranged in a crossβΞ² conformation. Microsc. Res. Tech. 67:210β217, 2005. Β© 2005 WileyβLiss, Inc.