Fig. 3.

Summary of the single particle reconstruction procedure for an average hepatic ferritin molecule core with an estimated iron loading of between 1100–1850 iron atoms. (a) An example of one of 133 HAADF images containing multiple ferritin cores, used for the reconstruction. (b) Absolute quantification of the iron atom content of a core using EELS correlates linearly with the normalised HAADF image intensity for a set of 16 ferritin cores with a range of different iron loadings. (c) Distribution of the iron content of 1241 ferritin cores in a tissue section showing a normal distribution with a mean of 1500 ± 300 iron atoms (upper and lower limits are 4,000 and 200 iron atoms). (d) Selected views of the initial models and final reconstructions (view 1–3) of a core developed from the 750 ferritin cores each with an iron atom content in the most populated range of between 1100–1850; despite different initial models a cubic-like subunit structure with a low density centre is evident in all of the final reconstructions. (e) The top row shows 750 core images all bandpass filtered, aligned and classified using the EMAN program into 9 of the 18 projection classes. The bottom row shows 9 re-projections, at 12° spacing, of the final reconstruction developed from initial model (a). The re-projections show strong correlation with the raw shape classes. In both cases the scale bar is 10 nm.