Puzzling peptides from a phage display library

The commercial availability of random peptide libraries displayed on the M 13 phage increased their use for studies on epitope identification, enzyme inhibitors and receptor ligands. We planed two experiments for selection of peptides. First, with sheep antibodies, the positive selector was IgG, prepared oh Protein G columns from a pool of 11 sheep protected with a vaccine prepared from larvae of Lucilia cuprina, against blowfly strike and the negative selectors were the IgG from the same sheep before vaccination and IgG from vaccinated sheep which were not protected. Four rounds of positive and negative selection were done respectively. In the second experiment, human IgG again prepared on new Protein G columns. Four rounds of positive selection with either IgG from MS or schizophrenia patients were done. They were alternated with two negative selections of schizophrenia IgG on the MS associated peptides and vice versa and two negative selections on each with the IgG from people who had died from non-nervous system diseases as control. After the fourth negative selection of each experiment, the phage were amplified and random clones were picked for nucleotide sequencing. A total of 44 peptides were sorted with the PILEUP program. From those, 15 peptides had a large number with either 4 or 5 methionines.