Selection of affinity reagents

A method of identifying an affinity reagent for an epitope, comprising:

• obtaining a first peptide library comprising a first plurality of at least 400 unique peptides, each peptide comprising a sequence of a formula αXβ, wherein X is the desired epitope, wherein the desired epitope X is a sequence of 2 to 20 amino acids, wherein the desired epitope X is identical among the first plurality of peptides, wherein α and β are flanking domains comprising known amino acid sequences;
• wherein the flanking domains α and β are any sequence of 1 to 10 amino acids, and wherein the flanking domains α and β vary among the first plurality of peptides;
• exposing the first peptide library to a plurality of affinity reagents, thereby binding at least one affinity reagent of the plurality of affinity reagents to the first peptide library, wherein an affinity reagent of the plurality of affinity reagents comprises oligonucleotides, peptimers, mini protein binders, antibodies, antibody fragments, or a combination thereof;
• determining the sequence or sequences of the at least one affinity reagents bound to the first plurality of peptides, thereby forming a reduced affinity reagent pool;
• obtaining a second peptide library comprising a second plurality of at least 400 unique peptides, each peptide comprising a sequence of a formula γXδ, wherein X is the desired epitope, wherein the desired epitope X is a sequence of 2 to 20 amino acids, wherein the desired epitope X is identical among the second plurality of peptides, wherein γ and δ are flanking domains comprising known amino acid sequences;
• wherein the flanking domains γ and δ are any sequence of 1 to 10 amino acids, and wherein the flanking domains γ and δ vary among the second plurality of peptides;
• exposing the second peptide library to the reduced affinity reagent pool, thereby binding at least one affinity reagent of the reduced affinity reagent pool to the second peptide library;
• and
• determining the sequence or sequences of at least one affinity reagent of the reduced affinity reagent pool bound to the second peptide library, thereby identifying an affinity reagent for the desired epitope X.