A Mossbauer determination of the iron core particle size distribution in ferritin

Abstract

The important biological Fe bearing molecule ferritin was studied using the 57Fe Mossbauer resonance. Natural and reconstituted ferritin samples were studied in the temperature range 4-300.degree. K. At low temperatures 6-line magnetic hyperfine spectra are observed but with noticeably asymmetric line shapes, at high temperatures doublets are observed and in an intermediate temperature range (30-40.degree. K) complex spectra characteristic of superparamagnetic behavior are observed. From a theoretical study of the dependence of the hyperfine splitting parameters on particle size and from the experimental probability distributions obtained for these parameters from the Mossbauer spectra it was possible to derive the ferritin micelle particle size distributions for 4 different samples. The natural and reconstituted samples have roughly similar distributions except for the sample reconstituted from apoferritin in the presence of phosphate. This sample has a slightly narrower particle size distribution centered on a smaller mean diameter. The information derived from these Mossbauer measurements is consistent with conclusions reached from separate biochemical experiments.