He proposed that the protein becomes infectious and destructive only when its shape is altered, and that this change occurs either through infection by an already infectious protein or through a genetic mutation. (ucsf.edu)
After 30 minutes, they began observing whether the injected material generated new infectious protein at the injection site. (sciencedaily.com)
But in the case of infectious proteins called prions, brittleness makes for a tougher, more menacing pathogen. (hhmi.org)