As proteins see more widespread commercial applications such therapeutic use, bioremediation and industrial catalysis, there is a greater need to improve our ability to enhance their properties and capabilities. Techniques such as directed evolution and computational design have proven effective as means of creating superior enzymes, however, these techniques are typically restricted to the canonical 20 “natural” amino acids. Conceptually expanding this to include synthetic or “unnatural” amino acids would allow for protein engineers to push past natural limits. Furthermore, it then becomes possible to introduce novel chemical, physical and fluoroscopic properties. This aims to elucidate the physiological parameters behind many neurological processes within the context of neurotransmitter mediated behaviours through the development of a protein based sensor. To do this, we are rationally engineering proteins to recognise and bind select neurotransmitters with the aid of ancestrally reconstructed templates. Furthermore, we are using a tetrazine unnatural amino acid to facilitate the addition of a small molecule fluorescent label in a regioselective manner, thereby allowing the development of a fluorescent-quenching based method of detecting ligand binding.