Figure 6.

Comparison of structure models and differences in density maps of AB₃ and AB₄ structures. (A) Workflow of data processing and refinement. (B) The electron density maps of the two models are depicted. For each model, the AB₃ (left) or AB₄ (right) unit cell is shown (inset). For comparison, the density is visualized at an r.m.s.d. of −0.207 e^–/nm³ for the AB₃ model and −0.220 e^–/nm³ for the AB₄ model. (C) Difference densities for the two structural types. The difference electron density for the AB₃ data was overlaid with the density map of the AB₄ model (left). Very little electron difference density (green) is observed around the protein shell, indicating that further density (= ferritin cage) is present. For the right panel, refinement with the AB₄ model shows a lot of negative electron density (red) for the position of the fourth ferritin, indicating that too much electron density is present in the model. Difference electron density visualized at an r.m.s.d. at 1.6 e^–/nm³.