Structure-activity relationships of [Nle4, D-Phe7]-MSH: discovery of a tripeptidyl agonist exhibiting sustained bioactivity - Sawyer, Tomi K; Castrucci, Ana Maria de Lauro; Staples, Douglas J; Affholter, Joseph A; De Vaux, Anne E.; Hruby, Victor J; Hadley, Mac E (Annals of the New York Academy of Sciences, 1993)