Sedimentation velocity analysis of PKR binding to a 40 bp dsRNA in AU75. (A) Raw sedimentation velocity profiles for 40 bp dsRNA. For clarity, only every 13th scan is shown. (B) Normalized g(s*) distributions of 0.03 μM 40 bp dsRNA (black), dsRNA + 0.05 μM PKR (blue), dsRNA + 0.3 μM PKR (red), dsRNA + 0.8 μM PKR (cyan), dsRNA + 2 μM PKR (green), dsRNA + 7 μM PKR (brown). (C) Global analysis of difference curves. The data were subtracted in pairs to remove systematic noise and the four data sets at the PKR concentrations were fit to a 2:1 binding model using SEDANAL (27). The top panels show the data (points) and fit (solid lines) and the bottom panels show the residuals (points). The best-fit parameters are shown in Table 1. For clarity, only every 7th difference curve of the 165 scans that were fit is shown.