Cellulose membranes spotted with 99 overlapping 13-mer PrP peptides were produced as previously described [36] . The membranes were blocked with 5% non-fat dry milk/tris-buffered saline containing 0.1% Tween 20 (TBST) probed with antibody diluted 1:5000 in 1% normal goat serum/TBS at 4uC overnight, followed by horseradish peroxidase (HRP)-conjugated goat antimouse secondary (Cappel 55570) for 2 hours at room temperature, and detected using Millipore Immobilon Western chemiluminescent HRP substrate (Cat WBKLS0500). Membranes were regenerated for re-use by shaking with dimethylformamide for 30 minutes, then 8M urea/50mM Tris-HCl pH 8.0/1% b-mercaptoethanol (b-MC)/1%SDS overnight at 37uC, followed by a 30 min wash in the same buffer, and then twice for 30 minutes each in 50% methanol/glacial acetic acid, and finally three times for 5 minutes each in methanol. After air drying membranes were stored in a sealed container at room temperature.