Amyloid Triangles, Squares, and Loops of Apolipoprotein C-III

[Image: see text] While a significant component of atherosclerotic plaques has been characterized as amyloid, the specific proteins remain to be fully identified. Probable amyloidogenic proteins are apolipoproteins (Apos), which are vital for the formation and function of lipoproteins. ApoCIII is an abundant protein implicated in atherosclerosis, and we show it forms a ribbonlike looped amyloid, strikingly similar to that previously reported for ApoAI and ApoCII. Triangles and squares with a width of ∼50 nm were also observed, which may be a novel form of amyloid or related to previously reported amyloid rings.