Protein scaffolds

A polypeptide display library comprising a recombinant polypeptide scaffold comprising:

• (i) seven beta strand domains designated A, B, C, D, E, F, and G, each having at least 95% homology to the amino acids of:
• a) SEQ ID NO:239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO:230 for the C beta strand, SEQ ID NO:
• 236 for the D beta strand, SEQ ID NO:
• 232 for the E beta strand, SEQ ID NO:
• 245 for the F beta strand and SEQ ID NO:246 for the G beta strand;
• or
• b) SEQ ID NO:239 for the A beta strand, SEQ ID NO:229 for the B beta strand, SEQ ID NO:247 for the C beta strand, SEQ ID NO:
• 236 for the D beta strand, SEQ ID NO:232 for the E beta strand, SEQ ID NO:248 for the F beta strand, and SEQ ID NO:234 for the G beta strand;
• (ii) linked to six loop regions such that a loop region connects each beta strand domain, is designated AB, BC, CD, DE, EF, and FG and corresponds to the cognate loop regions of SEQ ID NO:1, the cognate loop regions of SEQ ID NO:
• 1 consisting of residues:
• a) from 11 to 17 inclusive in an AB loop;
• b) from 23 to 31 inclusive in an BC loop;
• c) from 39 to 45 inclusive in an CD loop;
• d) from 51 to 56 inclusive in an DE loop;
• e) from 23 to 31 inclusive in an EF loop;
• f) from 23 to 31 inclusive in an FG loop,
• at least one of said loop regions being a non-naturally occurring variant of the cognate loop region in SEQ ID NO:
• 1;
• and
• (iii) a disulfide bond linking the F and G beta strand domains or linking the C and F beta strand domains.