Ψ and χ Angle Constrains at the C-Terminus Trp Position of the Melanotropin Tetrapeptide Ac-His-d-Phe-Arg-Trp-NH2 Lead to Potent and Selective Agonists at hMC1R and hMC4R. - Zhou Y; Mowlazadeh Haghighi S; Sawyer JR; Hruby VJ; Cai M (Journal of medicinal chemistry, 2023)