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Biochim Biophys Acta. 2010 Aug;1800(8):858-70. doi: 10.1016/j.bbagen.2010.03.012. Epub 2010 Mar 20.

The sedimentation properties of ferritins. New insights and analysis of methods of nanoparticle preparation.

Author information

1
Department of Chemistry, University of New Hampshire, Durham, NH 03824-2544, USA.

Abstract

BACKGROUND:

Ferritin exhibits complex behavior in the ultracentrifuge due to variability in iron core size among molecules. A comprehensive study was undertaken to develop procedures for obtaining more uniform cores and assessing their homogeneity.

METHODS:

Analytical ultracentrifugation was used to measure the mineral core size distributions obtained by adding iron under high- and low-flux conditions to horse spleen (apoHoSF) and human H-chain (apoHuHF) apoferritins.

RESULTS:

More uniform core sizes are obtained with the homopolymer human H-chain ferritin than with the heteropolymer horse spleen HoSF protein in which subpopulations of HoSF molecules with varying iron content are observed. A binomial probability distribution of H- and L-subunits among protein shells qualitatively accounts for the observed subpopulations. The addition of Fe(2+) to apoHuHF produces iron core particle size diameters from 3.8 + or - 0.3 to 6.2 + or - 0.3 nm. Diameters from 3.4 + or - 0.6 to 6.5 + or - 0.6 nm are obtained with natural HoSF after sucrose gradient fractionation. The change in the sedimentation coefficient as iron accumulates in ferritin suggests that the protein shell contracts approximately 10% to a more compact structure, a finding consistent with published electron micrographs. The physicochemical parameters for apoHoSF (15%/85% H/L subunits) are M=484,120 g/mol, nu=0.735 mL/g, s(20,w)=17.0 S and D(20,w)=3.21 x 10(-)(7) cm(2)/s; and for apoHuHF M=506,266 g/mol, nu=0.724 mL/g, s(20,w)=18.3S and D(20,w)=3.18 x 10(-)(7) cm(2)/s.

SIGNIFICANCE:

The methods presented here should prove useful in the synthesis of size controlled nanoparticles of other minerals.

PMID:
20307627
PMCID:
PMC2921680
DOI:
10.1016/j.bbagen.2010.03.012
[Indexed for MEDLINE]
Free PMC Article

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