Methods and compositions for identifying D-peptidic compounds that specifically bind target proteins

A method comprising:

• a) contacting a 50 residue or more D-target protein with a library of 50 residue or more distinct β1 domain of Protein G (GB1) L-peptidic compounds comprising a 4β-1α structural motif, wherein the compounds of the library are described by the formula β1-β2-α1-β3-β4 wherein β1, β2, β3 and β4 are independently beta-strand domains;
• and β1, β2, α1, β3, β4 are connected independently by linking sequences of between 1 and 10 residues in length, wherein the compounds of the library have at least 8 mutations outside of the β1-β2 and β3-β4 regions, wherein the compounds of the library have at least 10 conserved residues in the β1-β2 and β3-β4 regions, wherein the library is a phage display library, wherein the compounds of the library comprise between 20 and 80 residues;
• b) identifying a L-peptidic compound of the library that specifically binds to the D-target protein;
• and
• c) producing the D-peptidic compound of the identified L-peptidic compound.