Prion Polymers (IMAGE) Stowers Institute for Medical Research Caption Prion polymers of the functional human prion protein, ASC, expressed in baker's yeast cells. Prion phenomena occur because of the improbability of proteins acquiring ordered structure spontaneously. Credit Halfmann Lab Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.