Citation: Nathan Collins; Judith L. Flippen-Anderson; Ronald C. Haaseth; Jeffery R. Deschamps; Clifford George; Katalin K\"ov\'er; Victor J. Hruby (1996). Conformational Determinants of Agonist versus Antagonist Properties of [d-Pen2,d-Pen5]Enkephalin (DPDPE) Analogs at Opioid Receptors. Comparison of X-ray Crystallographic Structure, Solution 1H NMR Data, and Molecular Dynamic Simulations of [l-Ala3]DPDPE and [d-Ala3]DPDPE. Journal of the American Chemical Society, 118, pp. 2143-2152.