A binding agent to a target molecule, or method or kit where the binding agent is selected from a library where each variant has a circular permutation of the FHA domain where the rearrange does not substantially disrupt the FHA domain's beta-sheet scaffold or increase the stability of the beta-sheet scaffold. The randomized regions of the FHA domain include the endogenous binding interface the FHA domain, the region opposite of the endogenous binding interface, and the circular permutation region.