Rational design, usually guided by computational prediction, and selection from libraries of variants of natural proteins have been used with success in the engineering of novel non-natural receptors. Many of these engineered protein binders will find use in biotechnological, diagnostic and medical applications, sometimes in the place of natural antibodies.
Mathonet, P., & Fastrez, J. (2004). Engineering of non-natural receptors. Current Opinion in Structural Biology, 14(4), 505-511. https://doi.org/10.1016/j.sbi.2004.06.007 (Original work published 2004)