Electrophoretic Analysis of Thyroid lodoproteins in Highly Cross-Linked Polyacrylamide Gels

Abstract

The electrophoretic behavior of thyroglobulin and larger thyroglobulin-like iodo-proteins prepared from the hog thyroid was studied in polyacrylamide gels over a wide range of cross-linking degrees (C%). When examined at a constant total acrylamide monomer concentration (T%) of 5%., the mobility of 19S thyroglobulin decreased with increase in C below C=5%, whereas above C=5%, it increased markedly with increase in C, giving a minimum mobility at C=5%. Similar biphasic mobility curves were obtained with 27S and 37S thyroid iodoproteins. Furthermore, in a region above C=15%, at least two additional larger components which escaped detection in the gels with lower degrees of cross-linking appeared as separate bands. Ferguson plots constructed for thyroid iodoproteins at a higher constant C of 20%. gave straight lines intersecting at a common point at T=0%.. From the calculated slopes of the Ferguson plots, it has been established that the thyroid contains a series of multimers of 19S thyroglobulin as constituent iodoproteins. Structural parameters of highly cross-linked gels were estimated under the assumption that the gels would be predominantly composed of a random meshwork of gel beads.