Effect of host cell contaminants on the refolding of MB109. Isolated inclusion bodies, without SEC purification, were directly used to set up the refolding at 0.2 mg/mL. Black arrows indicate the refolded functional dimer. (A) Refolding at pH 7–10. The densitometry of the functional band in each condition is shown in black squares and lines. Gray squares and lines are the refolding results from Figure 2 for comparison. (B and C) Refolding in 0–4 M NaCl (B) and 0–4% CHAPS (C).