Configuration of the four iron atoms in dissolved human hemoglobin as studied by anomalous dispersion.

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Abstract
The anomalous dispersion of Fe at its K-absorption edge in small-angle scattering of an aqueous solution of Hb was used to establish the geometrical arrangement of the 4 Fe atoms in this protein. Although the anomalous contributions are 0.001-0.01 of the total scattering, experiments with synchrotron radiation from the storage ring DORIS showed that these effects can be measured with an average precision of .apprxeq. 10% at each of the 50 points of the scattering curve. The anomalous scattering represents the convolution of the whole structure with the configuration of the 4 Fe atoms of Hb. Analysis in terms of multipoles suggests that tetrahedral symmetry of both the subunit arrangement and the Fe atoms of 26 .ANG. derived from this experiment compared well with that derived from crystallographic data.