Fig. 3

Extrapolated form factors per unit mass from the experiments (symbols), consecutively scaled down by a factor of 2 for better visibility (iron free not scaled). The dashed lines show the best fitting calculated form factor from the structure models. The solid lines include a Guinier function in the calculated form factor to account for small protein aggregates, which results in a much better agreement with the experimental data at low Q. The inset magnifies the Q-range around 0.2 Å⁻¹ (without scaling), where the conformational change is most prominent. Errors are below 2 %. A concentration series of iron saturated pD5 and iron free samples are given in Additional file 1 S2a-d