IODINATION OF MOUSE EGF WITH CHLORAMINE-T AT 4-DEGREES-C - CHARACTERIZATION OF THE IODINATED PEPTIDE AND COMPARISON WITH OTHER LABELING METHODS

A modified Chloramine T labelling procedure was used to iodinate mEGF in order to perform radio-receptor assays. The reaction was conducted at 4 degrees C with 1 mu g Chloramine T only. The tracer obtained was characterized by its maximal binding, specific activity acid binding p roperties compared with the native peptide. Fast Liquid Protein Chroma tography was performed to analyse the homogeneity of the preparation a nd membrane extracts from A431 cells were used to purify the tracer. T he modified Chloramine T procedure was compared with two other methods : the classical Chloramine T iodination and the labelling procedure us ing Enzymobeads. The modified Chloramine T procedure is reproducible, provides labelled mEGF with high binding capacity (65 to 80% with cani ne placental membrane extracts) and high specific activity (351 +/- 10 7 mu Ci/mu g mEGF) and seems to preserve the binding properties of the native peptide.