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. 2012 Jul 11;7(7):e38314. doi: 10.1371/journal.pone.0038314

Figure 9. Increased proteinase K (PK) resistance of hPrP90–231 w.t. in the presence of increasing Ca++ concentrations.

Figure 9

hPrP90–231 w.t. was thermally denatured or preincubated with increasing concentration of Ca++ before being subjected to PK digestion with different enzyme concentrations. Partial resistance was evaluated in Western blot experiments using the anti-PrP antibody 3F4. Left panel shows representative immunoblots, while the graph on the right depicts the densitometry analysis of three independent experiments. Data are expressed as percentage of the respective recombinant peptide input. * = p<0.05 and ** = p<0.01 vs. control values. In native conditions or in the presence of low Ca++ concentrations, the peptide showed no resistance to PK digestion. After incubation with 5 or 10 mM Ca++ a partial resistance was observed for a peptide/PK ratio of 500∶1. Thermal denaturation induced a higher resistance as compared to Ca++ binding, being the immunolabeled peptide band detectable also for a peptide/PK ratio of 200∶1.