[Ala17]-MCH TFA, a selective ligand for MCHR 1 (K i =0.16 nM) over MCHR 2 (K i =34 nM), is an analogue of MCH. When labeled with a [Eu 3+ chelate], [Ala17]-MCH exhibits high affinity for MCHR 1 (K d =0.37 nM) and negligible binding affinity for MCHR 2.
