At present doctors test for the presence of abnormal proteins called prions which are thought to cause the disease by killing off brain cells.

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Scientists had long assumed that these disorders must be caused by a virus, but Prusiner had proposed back in 1982 that deformed proteins, called prions, were the culprit.

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Prusiner proved that prions are a deformed version of an otherwise harmless protein called PRP.

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Prions, beta-amyloid and synuclein, by contrast, are full of sticky structures called beta-sheets that react willy-nilly with crucial proteins.

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