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Clinical Chemistry 25: 989-995, 1979;
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Clinical Chemistry, Vol 25, 989-995, Copyright © 1979 by American Association for Clinical Chemistry

Heterogeneity of chloramine T- and lactoperoxidase-radioiodinated human calcitonin

WC Dermody, AG Levy, PE Davis and JK Plowman

Radioiodination reportedly damages peptides, but the nature of the damage has not been adequately examined. Utilizing isoelectric focusing, we examined the products of Chloramine T- and lactoperoxidase- directed radioiodinations of human calcitonin. Initially, the reaction products were purified by adsorption onto and elution from microfine silica (QUSO-G32). Radioiodination of the calcitonin by Chloramine T and lactoperoxidase produced a heterogeneous population of 125I-labeled peptides exhibiting apparent isoelectric points that were more acidic than that of unlabeled synthetic calcitonin. Variation in the products among radioiodinations and the inability of QUSO-G32 to resolve the components of the reaction mixture prompted our examination of alternative purification procedures. Anion-exchange chromatography on QAE-Sephadex effectively separated [125I]diiodotyrosine containing calcitonin from free iodine and [125I]iodolactoperoxidase. Our data indicate that: (a) radioiodination of human calcitonin by Chloramine T and lactoperoxidase induced alteration in the peptide as evidenced by isoelectric point, (b) specific [125I]iodopeptides vary in incidence and relative abundance among radioiodinations, (c) identification of the labeled amino acid in [125I]iodopeptides cannot ensure intergrity of the molecule, and (d) isoelectric focusing provides a method of comparing the products of peptide radioiodinations among laboratories.


The following articles in journals at HighWire Press have cited this article:


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 EndocrinologyHome page
R. Zhang, N. Scherberg, and L. J. DeGroot
Monoclonal Antibodies to Rat Calcitonin: Their Use in Antigenic Mapping and Immunohistochemistry
Endocrinology, April 1, 1997; 138(4): 1691 - 1696.
[Abstract] [Full Text] [PDF]


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Copyright © 1979 by the American Association for Clinical Chemistry.