Scheme 10. Unnatural Amino Acids Bearing a Chelating Group (i.e., Biypridine-alanine BpyA) Allow the Anchoring of Copper into Homodimeric Lactococcal Multidrug Resistance Regulator (LmrR), and Site-Directed Mutagenesis of Second Coordination Sphere Residues Leads to a Significantly Improved Artificial Hydratase.