Fig. 5.

PI3-SH3 pulse-labeled samples prepared under PF conditions. (A) ESI-MS mass spectra (+6 charge state). The spectra show the relative populations of D_agg (green band), O_agg (blue band), and F_agg (orange band) at the indicated Δt_agg times. Peak intensities are normalized to the overall species population. (B–D) Exchange profile for D_agg (B), O_agg (C), and F_agg (D). These profiles were obtained by multilinear regression analysis combining the NMR data of samples prepared after Δt_agg equal to 0, 2, 6, 10, 13, and 15 days and the distribution of populations obtained by ESI-MS. The bars represent the proton occupancy and percentage of exchange for each residue. The locations of the β-sheet strands, turns, and loops in the native state of PI3-SH3 are indicated above the graph. An asterisk above a bar indicates a residue whose resonance is not fully resolved; the absence of a bar indicates that the resonance of the residue is not detectable or that the residue is proline that does not have an amide hydrogen (residues 50, 70, and 84).