An overlapping peptide library can be used for linear or continuous epitope mapping, which can be used to figure out which part of a given protein or peptide contains the essential amino acids that contribute to its functionality. Characterized by two parameters, peptide length and offset number, each library is generated by dividing the original protein or peptide into many overlapping peptides of equal length. Optimum peptide length is 8 to 20 amino acids, and as a general guideline, a peptide must be at least six residues in length for it to cover an epitope. The offset number is the number of amino acid residues shared by adjacent peptides, and it reflects the degree of overlap.
Careful selection of the offset number and the peptide length can minimize experiment cost, while maximizing data value. The offset number is usually designed to be 1/3 of the peptide length. Long peptides will generate more epitope hits per peptide, but they are difficult to synthesize and the library will contain fewer peptides. Shorter peptides are easier and cheaper to synthesize, but will result in fewer epitope hits per peptide. The combination of low offset number and short peptide length generates the largest number of peptides, while the combination of high offset number and long peptide length produces the least number of peptides.
The overlapping peptide library has many applications. For example, the library can be used for the T-cell epitope determination in the areas of infectious diseases, oncology, and vaccine development.
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