The exogenous DNA fragment encoding the polypeptide is fused to the coding gene of the phage surface protein (inserted between the signal peptide and the capsid protein gene), and then presented as a fusion protein on the surface of the phage, each phage containing only one foreign gene. The displayed polypeptide or protein maintains relative spatial structure and biological activity and is displayed on the surface of the phage. A group of phage introduced with a variety of foreign genes constitutes a phage display library displaying a variety of exogenous peptides.
When a protein is used to screen a phage display library (the display library is the mobile phase, the screen protein is the stationary phase), it is selectively combined with an exogenous peptide that interacts with it to separate the display. A specific phage in Curry studies the biological function of the foreign gene contained in the phage.
Technological development
Classification and applicability
classification | applicability |
Single-strand filamentous phage display system | Suitable for display of peptide libraries |
T4 phage display system | Display complex proteins that cannot be secreted by E. coli |
Lambda phage display system | Active macromolecular protein (greater than 100 kDa), a protein that is toxic to the host |
T7 phage display system | Display cDNA library |
Phage display superiority
1. Provide a direct physical connection between the protein and its genetic information, and effectively screen and amplify the clones of the desired function.
2. The displayed polypeptide or protein structure function is close to the natural state, and the display material with high affinity with the target molecule can be easily and quickly screened.
3. During the screening process, specific phage clones are continuously enriched due to the deliberate affinity of their ligands, so that relatively rare clones that can bind ligands can be quickly and efficiently screened from a large library. come out.
4. Compared with other technologies, it is easy to screen libraries with large library capacity.
Phage display limitations :
1. The capacity of the peptide library is affected by the transformation efficiency of E. coli, and the capacity is generally 10 9 . More genes above this limit will be difficult to express;
2. The gene encoding the polypeptide has a certain codon preference, which limits the complexity of the peptide library;
3. The biosynthesis system of phage host E. coli has its own limiting factors, such as lack of amino acid modification, protein glycosylation, and inability to synthesize D-type amino acids.
4, in the process of phage display must undergo bacterial transformation, phage packaging, and some display systems have to undergo a transmembrane secretion process, which limits the molecular diversity of the library.
5. Not all sequences are well expressed in phage, because the realization of some protein functions requires folding, transport, membrane insertion and complexation, resulting in the selection pressure required for screening in vivo.
Application range
Cancer research and drug targeted therapy
Diagnostic vaccine development
Enzyme inhibitor screening
Construction of antibody/cDNA libraries
Study the biological process of protein-nucleic acid interaction
Research on novel gene targeting systems
Eg1: The heavy chain variable region gene was cloned from HBx (hepatocarcinoma-associated antigen) monoclonal antibody cells, recombined into M13 phage, and the expression product was verified to be active, and then single-chain antibody, single-domain antibody or chimeric antibody was expressed to guide liver cancer. Treatment research provides the basis.
Eg2: To solve the problem of weak immunological prototypes encountered in the preparation of vaccines for atypical Haemophilus influenza virulence factor surface protein mixed oligosaccharide LOS, the rabbit anti-LOS screening peptide library was used to obtain four consensus sequences, three of which were Rabbits have high anti-affinity. The antibody obtained by immunizing rabbits with the three high-affinity peptides obtained by screening has an antibody protective effect on the infected mouse model.
Jin Kairui Phage Platform is now offering antibody library construction services, antibody fragment library construction services, bispecific antibody customization services and antibody humanization services to provide you with a professional one-stop service to meet your actual needs!
Sexually Transmitted Disease Tests
If your sexual history and current signs and symptoms suggest that you have a sexually transmitted disease (STD) or a sexually transmitted infection (STI), your doctor will do a physical or pelvic exam to look for signs of infection, such as a rash, warts or discharge.
Laboratory tests can identify the cause and detect coinfections you might also have.
Blood tests.Blood tests can confirm the diagnosis of HIV or later stages of syphilis.
Urine samples.Some STIs can be confirmed with a urine sample.
Fluid samples.If you have open genital sores, your doctor may test fluid and samples from the sores to diagnose the type of infection.
It include the HIV 1/2 Test, Anti-syphilis test, Gonorrhea antigen test, Chlamydia Trachomatics antigen & antibody test.
Sexually Transmitted Disease Tests,Hiv Test,Chlamydia Trachomatis Test,Syphilis Test,Gonorrhea Antigen Test
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