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Six different procedures for radioiodination of mouse epidermal growth factor (EGF) all resulted in a heterogeneous 125I-labelled EGF preparation, as analysed by reversed-phase HPLC. EGF preparations that had been iodinated with Chloramine T, Iodogen(TM), or Iodo-beads(TM) were found mainly to consist of oxidised 125I-labelled EGF moieties. In contrast, the heterogeneous 125I-labelled EGF preparations obtained by using iodine monochloride, Pro-tag-125(TM), or lactoperoxidase-glucose oxidase-coupled beads (Enzymobeads(TM)) contained insignificant amounts of oxidised EGF entities. Ligand equivalence analysis (LEA) of distinct HPLC column fractions, obtained after preparative separation of Chloramine T-125I-labelled EGF, showed that the receptor-binding affinity of the tracer in all subfractions was less than the affinity of unlabelled EGF. This implies that HPLC purification of these 125I-labelled EGF preparations does not yield 125I-labelled EGF preparations with ligand equivalence. However, all but one HPLC column fraction of Enzymobeads-125 I-labelled EGF showed ligand equivalence. Despite the small amount of the nonequivalent component in the Enzymobeads-labelled tracer, the nonchromatographed 125I-labelled EGF preparation showed ligand equivalence. No significant differences were observed in the maximal binding capacity of the different 125I-labelled EGF preparations.

Additional information

Authors: KIENHUIS C B M, University Hospital Nijmegen (NL);HEUVEL J J T M, University Hospital Nijmegen (NL);BENRAAD T J, University Hospital Nijmegen (NL);ROSS H A, University Hospital Nijmegen (NL);FOEKENS J A, Dr. Daniel Den Hoed Cancer Center, Division of Endocrine Oncology, Rotterdam (NL)
Bibliographic Reference: Article: Clinical Chemistry, Vol. 38 (1992) No. 5, pp. 681-686
Record Number: 199211044 / Last updated on: 1994-12-02
Original language: en
Available languages: en