The electron density distribution (EDD) of a plant cyclic nonapeptide of orbitide type was studied. Crystal X-ray diffraction data was obtained from the Cambridge Structural Database (CSD) and refitted using scattering factors of the invariom library, thereby providing aspherical electron density. Bond topological, atomic properties and molecular surfaces (electrostatic potential and Hirshfeld surfaces) were derived. The partial double bond character of the peptide bond was confirmed by the ellipticity ε = 0.25. For eight N–H⋯O hydrogen bonds, atomic charges of contributing atoms differ depending on the type of the accepting oxygen atom. Atomic charge differences between negative main and positive side chains of this nonapeptide result in characteristic features of the electrostatic potential, which shows a positive isosurface around the molecule leading to repulsive interactions in the solid state structure. Weak intermolecular interactions are indicated by insignificant ED concentrations on the Hirshfeld surface except for weak signals at sites of intermolecular N–H⋯O and C–H⋯O hydrogen bonds.

中文翻译：

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轨道型植物环状九肽：电子密度研究

研究了轨道型植物环状九肽的电子密度分布（EDD）。晶体 X 射线衍射数据从剑桥结构数据库 (CSD) 获得，并使用 invariom 库的散射因子进行重新拟合，从而提供非球面电子密度。推导了键拓扑、原子性质和分子表面（静电势和赫什菲尔德表面）。通过椭圆度证实了肽键的部分双键特征ε= 0.25。对于八个 N–H⋯O 氢键，贡献原子的原子电荷根据接受氧原子的类型而不同。这种九肽的负主链和正侧链之间的原子电荷差异导致静电势的特征，这显示出分子周围的正等值面，导致固态结构中的排斥相互作用。赫什菲尔德表面上的 ED 浓度不显着，表明分子间相互作用较弱，除了分子间 N-H⋯O 和 C-H⋯O 氢键位点处的信号较弱。