Methods for production of unstructured recombinant polymers and uses thereof

A method of increasing serum secretion half-life of a protein, comprising:

• fusing said protein with one or more unstructured recombinant polymers (URPs), wherein the URP comprises at least about 40 contiguous amino acids, and wherein
• (a) the sum of glycine (G), aspartate (D), alanine (A), serine (S), threonine (T), glutamate (E) and proline (P) residues contained in the URP, constitutes more than about 80% of the total amino acids of the URP;
• and/or
• (b) at least 50% of the amino acids are devoid of secondary structure as determined by Chou-Fasman algorithm;
• and wherein said URP is substantially incapable of non-specific binding to a serum protein.

A method of detecting the presence or absence of a specific interaction between a target and an exogenous protein that is displayed on a genetic package, wherein said protein comprises one or more unstructured recombinant polymer (URP), the method comprising:

• (a) providing a genetic package displaying a protein that comprises one or more unstructured recombinant polymers (URPs);
• (b) contacting the genetic package with the target under conditions suitable to produce a stable protein-target complex;
• and
• (c) detecting the formation of the stable protein-target complex on the genetic package, thereby detecting the presence of a specific interaction.