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1. A thermostable recombinant CheBc domain comprising: (i) four framework regions designated FR1, FR2, FR3, and FR4, having at least 80% identity to the amino acid sequence of SEQ ID NO: 40 for FR1, SEQ ID NO: 41 for FR2, SEQ ID NO: 42 for FR3, and SEQ ID NO: 43 for FR4; (ii) the four framework regions connected by three loop regions, wherein said CheBc domain has three loop regions designated L1, L2, and L3, wherein L1, L2, and L3 structurally correspond to amino acids 43-47, 103-107, and 135-137 of SEQ ID NO: 1, respectively; wherein between one and three of said loop regions are randomized by deletion, substitution or addition such that each randomized loop region consists of between 6 and 15 amino acid residues; and wherein L1 is linked between FR1 and FR2, L2 is linked between FR2 and FR3, and L3 is linked between FR3 and FR4 to form a contiguous polypeptide comprising the arrangement FR1-L1-FR2 L2-FR3 L3 FR4, thereby forming a single linear polypeptide having a modified doubly wound α/β sandwich fold supersecondary structural region; wherein said CheBc domain binds a target with a determinable affinity of less than 1000 nM, and wherein said CheBc domain has a determinable melting temperature of at least 60 degrees Celsius.
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