Puzzling Peptides from a Phage Display Library

Document Type: Research Paper


1 Pathobiology Department, School of Veterinary Medicine, Ferdowsi University of Mashad, Mashhad, Iran.

2 Biotechnology Research Group, Murdoch University, Perth, Western Australia.


The commercial availability of random peptide libraries displayed on the M13 phage is increasing their use for
studies on epitope identification, enzyme inhibitors, receptor ligands, etc. In this study two experiments
where planned for selection of peptides. First with sheep antibodies, the positive selector was IgG, prepared
on Protein G column from a pool of 11 sheeps immunized, with a vaccine prepared from larvae of
Lucilia cuprina, against blowfly strike. The negative selector was IgG from the same sheeps before vaccination
and IgG from vaccinated non-immunized sheeps. Four rounds of positive and negative selections
with IgG from sheep were done respectively. In the second experiment using human IgG prepared on
a fresh Protein G column, again four rounds of positive selection with either IgG from MS and schizophrenia
patients were performed. This assay was alternated with two negative selections of schizophrenia IgG on
MS-associated peptides and vice versa and two negative selections on each with a control IgG. After the
fourth negative selection in each experiment, the phage was amplified and random clones were picked
for nucleotide sequencing. A total of 44 peptides were sorted with the PILEUP program and there was a large
number of 12-mer peptides containing either 4 or 5 methionine residues.