Selection of affinity reagents

1. 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.

2. The method of claim 1 , wherein α and β comprise the same amino acid sequence.

3. The method of claim 1 , wherein α and β comprise differing amino acid sequences.

4. The method of claim 1 , wherein α and β comprise differing amino acid sequences from γ and δ.

5. The method of claim 1 , wherein α and β comprise amino acid sequences with homogeneous chemical diversity.

6. The method of claim 5 , wherein the amino acid sequences with homogeneous chemical diversity comprise amino acid sequences comprising two or more amino acid side groups with equivalent electrical charge, hydrophobicity, hydrophilicity, steric size, polarity, molecular structure, or a combination thereof.

7. The method of claim 1 , wherein α and β comprise amino acid sequences with heterogeneous chemical diversity.

8. The method of claim 7 , wherein the amino acid sequences with heterogeneous chemical diversity comprise amino acid sequences comprising two or more amino acid side groups with differing electrical charge, hydrophobicity, hydrophilicity, steric size, polarity, molecular structure, or a combination thereof.

9. The method of claim 1 , wherein γ and δ comprise amino acid sequences with homogeneous chemical diversity.

10. The method of claim 9 , wherein the amino acid sequences with homogeneous chemical diversity comprise amino acid sequences comprising two or more amino acid side groups with equivalent electrical charge, hydrophobicity, hydrophilicity, steric size, polarity, molecular structure, or a combination thereof.

11. The method of claim 1 , wherein γ and δ comprise amino acid sequences with heterogeneous chemical diversity.

12. The method of claim 11 , wherein the amino acid sequences with heterogeneous chemical diversity comprise amino acid sequences comprising two or more amino acid side groups with differing electrical charge, hydrophobicity, hydrophilicity, steric size, polarity, molecular structure, or a combination thereof.

13. The method of claim 1 , further comprising washing the at least one affinity reagent of the plurality of affinity reagents bound to the first peptide library.

14. The method of claim 1 , further comprising washing the at least one affinity reagent of the reduced affinity reagent pool bound to the second peptide library.

15. The method of claim 1 , wherein the peptides within the first or second peptide library are in a native state.

16. The method of claim 1 , wherein the peptides within the peptide first or second library are in a non-native state.

17. The method of claim 1 , wherein the non-native state is a denatured state or a partially-folded state.

18. The method of claim 1 , comprising repeating one or more times the steps of exposing the first peptide library to the plurality of affinity reagents and determining the sequence or sequences of the at least one affinity reagents.

19. The method of claim 1 , comprising repeating one or more times the steps of exposing the second peptide library to the reduced affinity reagent pool and determining the sequence or sequences of the at least one affinity reagents.

20. The method of claim 1 , wherein an affinity reagent of the plurality of affinity reagents comprises an oligonucleotide.

21. The method of claim 1 , wherein X is a sequence of 3 amino acids.

22. The method of claim 1 , wherein X is a sequence of 4 amino acids.

23. The method of claim 1 , wherein X is a sequence of 5 amino acids.

24. The method of claim 1 , wherein X is a sequence of 6 amino acids.

25. The method of claim 1 , wherein the affinity reagent comprises an antibody or antibody fragment.

26. The method of claim 1 , wherein the affinity reagent comprises an aptamer.