Chatterjee A, Parthasarathy R
Int J Pept Protein Res. 1984 Nov;24(5):447-52.
Crystals of N-formyl-L-methionyl-L-valine (C11H20N2O)4S, M.W. = 276.3) are orthorhombic, space group )2(1)2(1)2(1) with cell constants at 294K of a = 4.851 (1), b = 14.925 (1), c = 19.745 (3) A, V = 1429.8 (1) A3, Z = 4 and observed (Dm) and calculated (Dx) of 1.49 and 1.488 g x cm-3, respectively. The crystal structure was solved using automatic diffractometer data (1260 reflections larger than or equal to 3 sigma) and refined to a final R-value of 0.035. This structure contains a short (2.626 (3) A) intermolecular hydrogen bond between the carboxyl OH and the N-acyl oxygen, a feature common to most N-acylamino acids and N-acylpeptides. The peptide is nearly planar (omega = 174.6 (5)); the values of psi 1, phi 2, psi 1T and psi 2T are, respectively, 131.8 (4) degrees, -139.9 (5) degrees, -39.3 (4) degrees and 142.1 (4) degrees. The methionine side chain is not zig-zag transplanar; the side chain torsion angles are: chi 1(1) = -60.0 (4) degrees, chi 2(1) = 176.0 (4) degrees and chi 3(1) = 71.8 (4) degrees. The two C gamma's for valine have psi 1-values of -64.4 (5) degrees and 173.7 (5) degrees. The formation of the parallel rather than antiparallel beta-sheet structure, the participation of the N-formyl group in the parallel beta-sheet and the use of C-H ... O hydrogen bonds to stabilize the beta-sheet are novel features found in this structure.
N-甲酰基-L-甲硫氨酰-L-缬氨酸（C11H20N2O）4S（分子量 = 276.3）的晶体为正交晶系，空间群为P2(1)2(1)2(1)，在294K时的晶胞参数为a = 4.851(1) Å，b = 14.925(1) Å，c = 19.745(3) Å，V = 1429.8(1) Å3，Z = 4，实测密度（Dm）和计算密度（Dx）分别为1.49和1.488 g·cm-3。晶体结构通过自动衍射仪数据（1260个大于或等于3σ的反射）解出，并精修至最终R值为0.035。该结构包含羧基OH与N-酰基氧之间短的（2.626(3) Å）分子间氢键，这是大多数N-酰基氨基酸和N-酰基肽共有的特征。肽几乎呈平面状（ω = 174.6(5)）；ψ1、φ2、ψ1T和ψ2T的值分别为131.8(4)°、 -139.9(5)°、 -39.3(4)°和142.1(4)°。甲硫氨酸侧链不是锯齿状平面构象；侧链扭转角为：χ1(1) = -60.0(4)°，χ2(1) = 176.0(4)°，χ3(1) = 71.8(4)°。缬氨酸的两个Cγ的ψ1值分别为 -64.4(5)°和173.7(5)°。该结构中发现的新颖特征包括形成平行而非反平行的β-折叠结构、N-甲酰基参与平行β-折叠以及利用C-H...O氢键稳定β-折叠。
