In-111 transferrin labeling studied by perturbed angular correlations.

The technique of perturbed angular correlations (P.A.C.) was used to study transferrin labeled with radioactive indium. Three forms of the labeled system were studied: a) the In-111 was bound to transferrin with no iron present at either of the binding sites; b) the In-111 probe was used to label transferrin that was 33% saturated with iron; and c) the label was attached to saturated Fe-transferrin. The measured perturbation factors, G22(t), indicate that the three binding states are clearly differentiated. Cases (a) and (b) exhibit characteristic features of time-independent quadrupole interactions and the average quadrupole interaction frequencies, omegaq, were determined in these cases.