Definition
The name amyloid comes from the early mistaken identification of the substance as starch (amylum in Latin), based on crude iodine-staining techniques. For a period, the scientific community debated whether or not amyloid deposits were fatty deposits or carbohydrate deposits until it was finally found that they were, in fact, deposits of proteinaceous material.
- The classical, histopathological definition of amyloid is an extracellular, proteinaceous deposit exhibiting beta sheet structure. Common to most cross-beta type structures they are generally identified by apple-green birefringence when stained with congo red and seen under polarized light. These deposits often recruit various sugars and other components such as Serum Amyloid P component, resulting in complex, and sometimes inhomogeneous structures. Recently this definition has come into question as some classic, amyloid species have been observed in distinctly intracellular locations.
- A more recent, biophysical definition is broader, including any polypeptide which polymerizes to form a cross-beta structure, in vivo, or in vitro. Some of these, although demonstrably cross-beta sheet, do not show some classic histopathological characteristics such as the Congo red birefringence. Microbiologists and biophysicists have largely adopted this definition, leading to some conflict in the biological community over an issue of language.
The remainder of this article will use the biophysical context.
Read more about this topic: Amyloid
Famous quotes containing the word definition:
“Was man made stupid to see his own stupidity?
Is God by definition indifferent, beyond us all?
Is the eternal truth man’s fighting soul
Wherein the Beast ravens in its own avidity?”
—Richard Eberhart (b. 1904)
“... if, as women, we accept a philosophy of history that asserts that women are by definition assimilated into the male universal, that we can understand our past through a male lens—if we are unaware that women even have a history—we live our lives similarly unanchored, drifting in response to a veering wind of myth and bias.”
—Adrienne Rich (b. 1929)
“The man who knows governments most completely is he who troubles himself least about a definition which shall give their essence. Enjoying an intimate acquaintance with all their particularities in turn, he would naturally regard an abstract conception in which these were unified as a thing more misleading than enlightening.”
—William James (1842–1910)