The ultrastructure of human thyroglobulin.

Thyroglobulin molecules purified in a single step procedure by gel filtration were studied in the electron microscope using the negative staining technique. The molecule had the shape of a flexible helix with two turns. Its length was about 220 A and the maximal diameter of the coiled part of the molecule was estimated to be 110 A. The pitch varied between 40 and 50 A. Thyroglobulin molecules dried in sodium tungstosilicate on a carbon film as for electron microscopy retained their hemagglutination-inhibiting activity and 19S sedimentation constant when redissolved in physiological buffer.