PRNP and scrapie: Nuclear magnetic resonance imaging studies in recombinant mouse PrP protein have shown that normal cellular PrP is structurally about 40% alpha helix and 3% beta-sheet, while analyses performed on the altered protein from sheep with scrapie revealed a significantly altered conformation, with 45% beta-sheet and 30% alpha helix [24], making the aggregated protein resistant to enzymatic digestion.