Srikrishnan T, Parthasarathy R
Biophysics Department, Roswell Park Cancer Institute, Buffalo, New York.
Int J Pept Protein Res. 1991 Oct;38(4):335-9. doi: 10.1111/j.1399-3011.1991.tb01512.x.
Crystals of N-formyl-L-alanyl-L-aspartic acid (C8H11N2O6) grown from aqueous methanol solution are orthorhombic, space group, P2(1)2(1)2(1) with cell parameters at 294K of a = 13.619(2), b = 8.567(2), c = 9.583(3)A, V = 1118.1A3, M.W. = 232.2, Z = 4, Dm = 1.38 g/cm3 and Dx = 1.378 g/cm3. The crystal structure was solved by the application of direct methods and refined to an R value of 0.075 for 1244 reflections with I greater than or equal to 3 sigma collected on a CAD-4 diffractometer. The structure contains two short intermolecular hydrogen bonds: (i) between the C-terminal carboxyl OH and the N-acyl oxygen (2.624(3)A), a characteristic feature found in many N-acyl peptides and (ii) between the aspartic carboxyl OH. and the peptide oxygen OP1 (2.623(3)A). The peptide is nonplanar (omega = 165.5(6) degrees). The molecule takes up a folded conformation in contrast to N-formyl peptides which form extended beta-sheets; the values of phi 1, psi 1, phi 2, psi 2(1), and psi 2(2) are, respectively -65.7(6), 152.0(5), -107.2(5), 30.9(5), and -150.3(6). The aspartic acid side chain conformation is g- with chi 1 = 73.1(5). The formyl group, as expected, is transplanar [OF-CF-N1-CA1 = -4.0(8) degrees]. The presence of the short O-H ... O hydrogen bond emerges as a structural feature common to this peptide and several other N-formyl peptides. There are no C-H ... O hydrogen bonds in this structure.
从甲醇水溶液中生长出的N-甲酰基-L-丙氨酰-L-天冬氨酸（C8H11N2O6）晶体为正交晶系，空间群为P2(1)2(1)2(1)，在294K时的晶胞参数为：a = 13.619(2)，b = 8.567(2)，c = 9.583(3)埃，V = 1118.1埃³，分子量 = 232.2，Z = 4，Dm = 1.38克/立方厘米，Dx = 1.378克/立方厘米。通过直接法解析晶体结构，并对在CAD-4衍射仪上收集的1244个I大于或等于3σ的反射进行精修，R值为0.075。该结构包含两个短的分子间氢键：（i）在C端羧基的OH与N-酰基氧之间（2.624(3)埃），这是许多N-酰基肽中发现的特征；（ii）在天冬氨酸羧基的OH与肽氧OP1之间（2.623(3)埃）。该肽是非平面的（ω = 165.5(6)度）。与形成伸展β-折叠的N-甲酰基肽不同，该分子呈折叠构象；φ1、ψ1、φ2、ψ2(1)和ψ2(2)的值分别为-65.7(6)、152.0(5)、-107.2(5)、30.9(5)和-150.3(6)。天冬氨酸侧链构象为g-，χ1 = 73.1(5)。如预期的那样，甲酰基是共平面的[OF-CF-N1-CA1 = -4.0(8)度]。短的O-H...O氢键的存在是该肽和其他几种N-甲酰基肽共有的结构特征。该结构中不存在C-H...O氢键。
