Can the library be amplified for additional panning experiments?
We strongly recommend against amplification of the supplied libraries, as sequence biases in vivo will likely result in certain sequences being underrepresented in the resulting library, or absent altogether. Displayed peptides in the Ph.D. libraries are expressed as fusions to the coat protein pIII, which modulates infectivity by binding to the F-pilus of the recipient cell. As a result, there is a biological selection against certain displayed sequences during in vivo amplification, particularly sequences with multiple positive charges (which inhibit secretion) and unpaired cysteines. The supplied libraries have each been amplified only once following ligation, and all characterization (representative sequencing, panning etc.) carried out on this amplified selling stock. We cannot guarantee that the amino acid distribution data we report for each library as supplied will hold upon reamplification.
