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Abstract

By exposing different sites of the 'head activator', different sets of antibodies were designed and produced which recognised either the amino or the carboxy terminus of the free 'head activator', which reacted with 'head activator' in a tissue-fixed conformation, or which bound to the 'head-activator' sequence, if it was part of a larger precursor-like molecule. An enzyme-linked immunosorbent assay (ELISA) was developed to characterise the antibodies and also to assay minute amounts of 'head activator' or 'head-activator'-like immunoreactivities in animal or tissue extracts. A competitive ELISA is described which uses biotin-avidin for enhancement. The assay is sensitive with an antibody specific for the amino terminus in the range of 0.5-50 fmol, with an antibody specific for the carboxy terminus in the range of 20-400 fmol. The ELISA specific for the amino terminus is 10-times more sensitive than a radio-immunoassay with tritiated 'head activator' [H. Bodenmüller and B. Zachmann (1983) FEBS Lett. 159,237-240]. Previously no radioimmunoassay existed with specificity for the carboxy terminus.