Taken together the structural analyses confirm the incorporation of Bpy at position 111 and the binding of Cu(II) to the Bpy moieties in both SCP ArMs. They also revealed marked differences in the environments of the Bpy and bound Cu(II) ions in the SCP_Q111BpyAla and SCP_Q111CBpy structures. Moreover, the Bpy moiety at position 111 is more rigid when incorporated as the unnatural amino acid BpyAla than via bioconjugation at a cysteine.