Phage display is a powerful technique used in the screening and transforming functional peptides and proteins. It is widely applied to multiple field of biology, including proteomics and cloning.
Since first appeared in the year of 1985, phage display has never receded in the magical molecular world. On the contrary, it is widening its range of activity.
Phage display technology is now in the track of rapid development. It plays an irreplaceable place in the epitope positioning, tumour antigens determination and interaction partners of a protein, making artificial antibodies and vaccines, diagnostic technique and other fields of related biotechnology researches.
However, the starting point of phage display technology is usually the construction of its library. There are many branches in this special library, the most common ones of which are peptide library, protein library and antibody library obtained commercially or constructed in-house. Proteins of interest can be selected from a protein library like pre-made phage libraries expressing on their surfaces proteins from microorganisms. The mission of a protein library is to select proteins with a specific function or affinity to anotherr molecule of interest such as the shotgun phage display system. While, the most important function of this technology has been the selection of phage display antibodies from antibody libraries. The antibody library expresses the phage display antibodies commonly as scFv or Fab fragments.
Inserting DNA fragments into phage or phagemid genomes on which phage coat the proteins are expressed is usually the way of accomplishing its construction. Many groups and institutions are engaged in the research and development of it. Commonly, institutions and researchers can generate libraries with a diversity of n×108, but some may build larger ones, Creative Biolabs, for instance. It is professional in construction of various phage display libraries like cDNA libraries, peptide libraries and scFv/Fab antibody libraries. Especially, they are able to generate libraries of n×109-10. In terms of peptide libraries with inserts longer than 8-mer while up to 30-mer, it usually utilize one of these three nucleotide doping strategies to maximize the amino acid sequences encoded by the inserted DNA sequences, NNK, Split-mix-split synthesis or Tri-mer codon. In addition, they can make both pIII-fusion libraries and pVIII-fusion libraries. For scFv/Fab library construction, they use both human plasma cells and splenocytes from immunized mice. Learn more about phage display library.
Together with this technique, phage display library screening is also helpful in related biological fields. Similar to phage display libraries, institutions and researchers normally get scFv/Fab antibodies of an affinity of 10-7 by conducting library screening or panning for 4 cycles. However, for Creative Biolabs, its proprietary protocol allows an increase of the affinity of the scFv antibodies from 10-8 to 10-9. They have successfully obtained a scFv antibody that has an extremely high affinity of 10-12. Learn more.