A crystal molecular conformation of leucine‐enkephalin related to the morphine molecule

Abstract

Leucine‐enkephalin (Try¹‐Gly²‐Gly³‐Phe⁴‐Leu⁵) has been crytallized as a trihydrate from water solution. X‐ray diffraction reveals a tightly folded molecular conformation with two fused βIII‐ (Gly²‐Gly³) and βI‐ (Gly³‐Phe⁴) turns. The Tyr¹ and Phe⁴ aromatic rings have a close orthogonal arrangement analogous to the tyramine and cyclohexenyl rings in morphine. This suggests that the conformation found in the trihydrate crystal structure could be required for recognition by μ‐receptor sites.