A new type of synthetic peptide library for identifying ligand-binding activity was reported last year (Nature 354:82-84, 1991). The method involves the chemical synthesis of a random peptide library on polyacrylamide beads using a 'pool & split synthesis approach'. A peptide library generated by this method results in each bead containing only a single peptide. The purpose of this experiment was to utilize this new technology to determine epitopes of the correspondent antibodies or allergens. The experiment involves: (1) designing an organic and water compatible linker, which could stand the organic acidity and basicity during the synthesis as well as the aqueous basicity during the antibody recognition; (2) using standard Fmoc-chemistry to perform peptide synthesis on polyacrylamide beads; (3) incubating the peptide library with a reporter coupled molecules; (4) sequencing the oligopeptide on corresponding beads. The preliminary result looks successful. The color indication shows clear positive and negative differences using a monoclonal antibody which binds to a known amino acid sequence. We have now synthesized a random peptide library on beads, screened it with monoclonal antibody with unknown epitopes specificity, and are subsequently sequencing the positive beads. With an apple fruit cDNA library in hand we can also clone the apple allergenic proteins using the peptide sequence information which are obtained from epitope library when screen with patient serum.
