Subramanian E, Sahayamary J J
Department of Crystallography and Biophysics, University of Madras, India.
Int J Pept Protein Res. 1989 Sep;34(3):211-4. doi: 10.1111/j.1399-3011.1989.tb00232.x.
The crystal structure of a tripeptide, L-phenylalanyl-glycyl-glycine (C13H17N3O4), molecular weight = 279.3, has been determined. The crystals are orthorhombic, space group P2(1)2(1)2(1), with a = 5.462(1) A, b = 15.285(5), c = 16.056(4), Z = 4, and P (calc) = 1.384 g.cm-3. The final R-index is 0.052 for 866 reflections with sin theta/lambda less than or equal to 0.55 A-1 and I greater than 1 sigma. The molecule exists as a zwitterion, with the N-terminus protonated and the C-terminus in an ionized form. Both the peptide units are in the trans configuration and planar, though one of them shows significant deviations from planarity ([delta w[ = 5.1 degrees). The peptide backbone is folded, with the torsion angles of: psi 1 = 116.2(5) degrees, omega 1 = 178.8(4), phi 2 = -89.7(5). psi 2 = -28.9(6), omega 2 = -174.9(4), phi 3 = 134.9(5), psi 31 = 7.8(6), psi 32 = -172.6(4). The terminal glycine adopts a "D-residue" conformation. For the sidechain of phenylalanine, chi 1 = 175.5(4), chi 2 = -127.0(6).
已测定三肽L-苯丙氨酰-甘氨酰-甘氨酸（C13H17N3O4）的晶体结构，分子量为279.3。晶体为正交晶系，空间群P2(1)2(1)2(1)，a = 5.462(1) Å，b = 15.285(5)，c = 16.056(4)，Z = 4，P（计算值）= 1.384 g.cm-3。对于866个sin θ/λ小于或等于0.55 Å-1且I大于1σ的反射，最终R指数为0.052。该分子以两性离子形式存在，N端质子化，C端呈离子化形式。两个肽单元均处于反式构型且为平面结构，不过其中一个显示出明显的平面度偏差（[δw[ = 5.1°）。肽主链呈折叠状，扭转角为：ψ1 = 116.2(5)°，ω1 = 178.8(4)，φ2 = -89.7(5)，ψ2 = -28.9(6)，ω2 = -174.9(4)，φ3 = 134.9(5)，ψ31 = 7.8(6)，ψ32 = -172.6(4)。末端甘氨酸采用“D-残基”构象。苯丙氨酸侧链的χ1 = 175.5(4)，χ2 = -127.0(6)。
