Doi M, Tanaka M, Ishida T, Inoue M, Fujiwara T, Tomita K, Kimura T, Sakakibara S, Sheldrick G M
J Biochem. 1987 Feb;101(2):485-90. doi: 10.1093/oxfordjournals.jbchem.a121934.
The crystal structure of [(4-bromo)Phe4,Met5]enkephalin (Tyr-Gly-Gly-(4-bromo)-Phe-Met) shows two independent molecular conformations. The molecules are arranged in parallel in a head-to-tail fashion and form an antiparallel beta-sheet structure involving intermolecular hydrogen bonds. This dimeric beta-structure is also observed in the [Met5]enkephalin crystal, in spite of their different crystal packing environments, which shows the energetic stability of this molecular conformation. The three-dimensional similarity between the dimeric beta-structure and the beta-turn form is discussed in the relation to the opioid delta and mu receptors.
[(4-溴)苯丙氨酸4，甲硫氨酸5]脑啡肽（酪氨酰-甘氨酰-甘氨酰-(4-溴)-苯丙氨酰-甲硫氨酸）的晶体结构显示出两种独立的分子构象。分子以头对头、尾对尾的方式平行排列，并形成涉及分子间氢键的反平行β-折叠结构。尽管[甲硫氨酸5]脑啡肽晶体的晶体堆积环境不同，但在该晶体中也观察到了这种二聚体β-结构，这表明了这种分子构象的能量稳定性。讨论了二聚体β-结构与β-转角形式之间的三维相似性与阿片δ和μ受体的关系。
