Phage display technology is an in vitro screening technology that can screen target peptides from a large number of peptide libraries and display the peptides on the surface of phages. The phage currently widely used for display is the M13 phage display system, which consists of 5 capsid proteins. The function of the capsid protein pⅢ is mainly screening. The target peptide gene can be inserted into pⅢ, and its applicable vector range is also very wide. According to the type of library, phage display peptide libraries are divided into random peptide libraries, cDNA libraries, antibody libraries, and protein libraries. Among them, the random peptide library is a library containing a large number of random sequence peptides generated by chemical synthesis or gene synthesis methods, which is mainly used to screen peptides that bind to specific target molecules. The random peptide library contains a combination of all possible arrangements of 20 amino acids. Because these peptide sequences are full of randomness, the random peptide library contains a large number of different peptides, and more peptides with specific functions or interactions can be discovered through the random peptide library.

Construction of Random Peptide Library:

The construction of random peptide library is mainly based on phage surface display technology. After inserting exogenous genes into phage vectors, the polypeptides encoded by the exogenous genes can be expressed on the phage surface, thereby constructing a library containing a large number of random peptides. The random peptide library contains a large number of peptide sequences with different lengths, amino acid compositions and structures, and they may interact with specific proteins. Using random peptide libraries, peptides with specific functions can be screened from a large number of peptides. In 1985, phage display technology was created. As a technology for studying antigen epitopes, phage display mainly uses genetic engineering technology to insert exogenous genes into phage capsid proteins, so that the polypeptides encoded by exogenous genes can be displayed as fusion proteins, and their own structure and activity do not change. After that, multiple rounds of screening are used to select highly specific antibodies or peptides that can bind to target molecules. In 1990, a random 6-peptide library based on phage display technology was created. After years of development, phage display technology has been used in the fields of cell signal transduction, protein recognition sites, and drug development in addition to studying antigen epitopes. With the widespread use of phage display technology, many diseases are determined by phage display technology. For example, a short antigenic peptide related to ankylosing spondylitis was discovered through a phage random 12-peptide library, and a peptide that may be a marker for colon cancer was also discovered in the serum of colon cancer patients through phage display technology. The capacity of the peptide library established based on phage display technology is as high as billions. In terms of screening peptide markers, phage display peptide libraries have the advantages of being fast, relatively low cost, and large library capacity. By screening phage peptides that bind to specific antigens, new antibodies can be developed or existing antibodies can be improved. Phage display peptides can also be used for vaccine development, cancer diagnosis, and biosensor development.

Fig.1 Positive clone identification diagram of random peptide library screening results

Fig. 2 Comparison diagram of peptide sequences encoded by positive clones

Preparation Method of Random Peptide Library:

Random peptide library can be synthesized by various methods, such as solid phase synthesis, genetic engineering, chemical synthesis, combinatorial chemistry, bioinformatics, etc. Solid phase synthesis is to add amino acids to a solid phase carrier and use different protective groups to combine peptide sequences to synthesize peptide fragments. The sequence and length of the peptide can be adjusted by solid phase synthesis. It is mainly used for the construction of random peptide libraries with specific sequence requirements. The genetic engineering method uses the genomic DNA of the organism as the raw material, and after enzyme cutting, ligation, etc., the random DNA fragment is inserted into the expression vector, and then expressed in the host cell to generate a random peptide library. The genetic engineering method can produce a large number of peptides with different sequences and different lengths. It is widely used in high-throughput screening of peptides and the discovery of new bioactive molecules. Through chemical synthesis, peptide fragments can be directly synthesized to construct random peptide libraries, and different protecting groups can adjust the sequence and length of peptides to a certain extent. Combinatorial chemistry uses a variety of chemical reactions to generate a large number of peptides with different sequences to construct random peptide libraries. This method can quickly generate a large number of peptides and is suitable for high-throughput screening of peptides. Using bioinformatics analysis methods, the sequence and structure of random peptides can be designed and predicted, and then random peptide libraries can be constructed by genetic engineering. Combining bioinformatics with other methods can comprehensively consider factors such as peptide diversity, stability and biological activity, making the design and construction of random peptide libraries more comprehensive.

TekBiotech is committed to providing customers with high-quality peptide library construction technology services, and providing strong support for customers' subsequent peptide library synthesis and screening, targeted peptide drug discovery, specific blocking peptide drug development, specific lead sequence development and other downstream research and development work. TekBiotech has rich project experience and insights in peptide library construction. After years of development, TekBiotech has established a complete peptide library construction system, including the M13 phage display system, M13 KE phage display system, T7 phage display system, etc., which rely on M13 helper phage. It can provide customers with high-quality linear peptide libraries (including but not limited to 6-peptide library, 7-peptide library, 12-peptide library, 15-peptide library) and cyclic peptide libraries (cyclic 6-peptide library, cyclic 7-peptide library, cyclic 10-peptide library, etc.) and other types of peptide library construction services. The M13 phage peptide library established by TekBiotech has a library capacity of up to 10^8 and a titer of up to 10^13 phage display peptide particles/ml. The T7 phage peptide library has a library capacity of up to 10^8 and a titer of up to 10^11 phage display peptide particles/ml, which is sufficient to support customers' subsequent screening of targeted peptides for various targets and meet downstream experimental needs. TekBiotech can provide one-stop technical services ranging from peptide gene library design and synthesis, peptide library construction to supporting peptide library screening, affinity verification, in vitro cell verification, etc. Customers only need to provide specific project requirements, and TekBiotech scientists will design the best library construction method and phage system according to the customer's project requirements to meet the customer's project needs.