Benedetti E, Pedone E M, Kawahata N H, Goodman M
CNR Department of Chemistry, University of Naples, Federico II, Italy.
Biopolymers. 1995 Nov;36(5):659-67. doi: 10.1002/bip.360360511.
The crystal structure of the hydantoin 1-[(S)-1'-aminoethylmalonyl benzyl ester]-(S)-4-methylimidazolidin-2,5-dione (1) derived from the peptide H-Ala-gAla-mGly-OBzl, having the retro-inverso modification of the Ala-Gly bond, has been determined by x-ray diffraction analysis. The crystals are orthorhombic, space group P2(1)2(1)2(1) with a = 6.539, b = 14.721, c = 17.101 A, z = 4. The structure was solved by direct methods and refined with anisotropic thermal factors to a final R value of 0.067 for the 947 observed reflections. Reversal of the Ala-Gly amide bond perturbs the folding tendency of the backbone shown by the parent peptide t-BuCO-Ala-Gly-NHiPr. The gem-diamino residue, gAla, and the malonyl moieties are found in the helical and the extended conformations, respectively. Intramolecular hydrogen bonding is not observed. The molecules in the crystal are held together by the formation of two intermolecular hydrogen bonds of the N-H ... O=C type with N ... O distances of 2.86 and 3.17 A, respectively.
对源自肽H-Ala-gAla-mGly-OBzl且具有丙氨酸-甘氨酸键反向异构修饰的乙内酰脲1-[(S)-1'-氨基乙基丙二酰苄酯]-(S)-4-甲基咪唑烷-2,5-二酮(1)的晶体结构进行了X射线衍射分析。晶体为正交晶系，空间群P2(1)2(1)2(1)，a = 6.539，b = 14.721，c = 17.101 Å，z = 4。结构通过直接法解析，并采用各向异性热因子进行精修，对于947个观测反射，最终R值为0.067。丙氨酸-甘氨酸酰胺键的反转扰乱了母体肽t-BuCO-Ala-Gly-NHiPr所呈现的主链折叠趋势。偕二氨基残基gAla和丙二酰部分分别呈螺旋构象和伸展构象。未观察到分子内氢键。晶体中的分子通过形成两个N-H...O=C型分子间氢键结合在一起，N...O距离分别为2.86和3.17 Å。
