Fig 4 -

Differential •OH modification of amino acid side chains in MM1 (red), MM2 (blue) and VV2 (yellow) brain-derived sCJD prions (a) before and (b) after synchrotron irradiation. (a) Degree of modification of specific residues before synchrotron irradiation was calculated as described for synchrotron irradiated samples. (b) •OH modification half-life of specific amino acid side chains in MM1 (red), MM2 (blue) and VV2 (yellow) calculated from fitting the fraction of unmodified data using first order rate constant equation. The complete protection of residues in MM1 prions is indicated by red line; the green line indicates high modifications rates due to the solvent exposure. The values are expressed as mean ± SEM from two independent irradiation experiments and three MS/MS peptide datasets for each time point. *, p < 0.05; **, p < 0.01; and ***, p < 0.001.