Biological+library+methods

Biological Library Methods

Biological library methods involve the use of biotechnology techniques and are generally used to synthesize polypeptide libraries (both proteins and peptides). DNA fragments containing the genes for proteins/peptides of interest are inserted into suitable vectors such as //Escherichia// //coli// filamentous bacteriophages . These vectors are then inserted into the genome or plasmids of microorganisms such as //E. coli. // The microorganisms transcribe these DNA fragments along with their own genome and as a result, the proteins/peptides of interest are translated. In order to easily screen the polypeptide of interest, it is ensured that the expressed polypeptides are on the surface of the microorganisms [2] .

 Figure 1[2] : A schematic representation of the steps that are undertaken during production of combinatorial libraries using biological library methods. Each step is discussed in detail on top of the figure. After the construction of the library, the polypeptides produced are screened using biopanning. In biopanning the microorganisms containing the expressed polypeptides of interest are incubated with a target, such as a specific antibody, which is bound to a solid support [2 ] . As a result, the polypeptides that have the highest affinity for the antibody can be selected, and the unbound microorganims are washed away. The eluted microorganisms that have high affinity for the specific antibody are regrown two or more times, in order to get ample amount of desired polypeptide [2]. The DNA of these regrown microorganisms is extracted and the portion of the DNA that codes for the polypeptide is screened to identify a consensus polypeptide sequence. If a consensus polypeptide sequence is found, the polypeptides are synthesized and tested for their binding capacity to determine the sequence which has the highest affinity for the antibody [2] .

Figure 2<span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 11px; vertical-align: super;">[2] : The schematic representation of biospanning process. The details of each step are discussed on top of the figure. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;"> The major advantages of using biological library methods is that polypeptide libraries are easy and economical to generate, using this method<span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 11px; vertical-align: super;">[2]. The major disadvantage of using biological library methods to produce polypeptide libraries is that only natural L-amino acids can be incorporated into the polypeptide being synthesized. This is because microorganisms that are used to replicate the polypeptides cannot incorporate unnatural amino acids (D-amino acids) or other organic subunits <span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 11px; vertical-align: super;">[2].

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