Nature Nanotechnology 7, 459–464 (2012); published online 17 June 2012; corrected after print 22 October 2012; corrected after print 27 November 2012.

In the version of this Letter originally published, Fig. 1a was incorrect and in Fig. 1c the wrong TEM image was used, they should have appeared as shown below.

Figure 1: Preparation and characterization of M-HFn nanoparticles.
figure 1

a, Schematic showing the preparation of M-HFn nanoparticles and their structure. c, TEM image of HFn protein shells.

Full size image

In the Supplementary Information, one of the authors was not mentioned in the author list: Lina Song has now been added. In the section 'Preparation and characterization of M-HFn particles' the column used for size-exclusion chromatography was incorrect: it should have been 'Sepharose 6B'. The synthesis procedure for M-HFn nanoparticles was incorrect: it should have read 'HFn protein shells were used as a reaction template to synthesize iron oxide nanoparticles according to the method reported by Cao et al.2 with some modification. The solution of 50 ml 100 mM NaCl with HFn (1 mg ml−1) was added to the reaction vessel, synthesized at 65 °C and pH 8.5. Fe(II) (25 mM (NH4)2Fe(SO4)2•6H2O) and stoichiometric equivalents (1:3 H2O2:Fe2+) of freshly prepared H2O2 (8.33 mM) were added. Fe(II) was added in a rate of 100 Fe/(protein min) using a dosing device (800 Dosino) connected with 842 Titrando. After theoretical 5000 Fe/ protein cage were added to the reaction vessel, the reaction was continued for another 5 min. Finally, 200 μl of 300 mM sodium citrate was added to chelate any free iron. The synthesized magnetite-containing HFn (M-HFn) nanoparticles were centrifuged and purified through size exclusion chromatography to remove the aggregated nanoparticles. The concentration of M-HFn nanoparticles was assumed to be the same as that of HFn protein and was determined using a BCA protein assay kit (Pierce). Purified M-HFn nanoparticles were obtained with a yield of about 75%.' Reference 2 was incorrect and should have read Cao, C. Q. et al. Magnetic characterization of noninteracting, randomly oriented, nanometer-scale ferrimagnetic particles. J. Geophys. Res. 115, B07103 (2010).