Core-level electronic structure of solid-phase glycine, glycyl-glycine, diglycyl-glycine, and polyglycine: X-ray photoemission analysis and Hartree-Fock calculations of their zwitterions.
Core-level electronic structure of solid-phase glycine, glycyl-glycine, diglycyl-glycine, and polyglycine: X-ray photoemission analysis and Hartree-Fock calculations of their zwitterions.
复制标题
固相甘氨酸、甘氨酰-甘氨酸、二甘氨酰-甘氨酸和聚甘氨酸的核心级电子结构：其两性离子的 X 射线光电子发射分析和 Hartree-Fock 计算。
DOI：
10.1063/1.2976151
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
K. Leung
中科院分区：
文献类型：
--
作者：
A. Chatterjee;Liyan Zhao;Lei Zhang;D. Pradhan;Xiaojing Zhou;K. Leung
用X射线光电子能谱(XPS)研究了甘氨酸(G)及其多肽(甘氨酰-甘氨酸(GG)、二甘氨基-甘氨酸(GGG)和聚甘氨酸(Poly-G))的核心级电子结构。增加多肽中G单元的数量不会改变对应于不同官能团的相应C 1S、N 1S和O 1S特征的位置：-COO(-)、-NH(3)(+)、>；CH(2)和-ConH-。用量子力学和分子力学方法计算了这些分子在周期性边界条件下作为孤立分子和水环境中的分子的电子结构。在甘氨酸两性离子的情况下，在Koopmann近似的背景下，C1S、N1S和O1SXPS特征的结合能与Hartree-Fock自洽场计算得到的轨道能量符合得很好。然而，对于较大的两性离子(与本工作中所考虑的特定构象)，结合能的一致性被发现得相当差，这表明需要更高水平的计算。本文的工作表明，在周期性边界条件下，用分子力学优化水环境中的两性离子可能是计算大型、复杂生物分子体系电子结构的一种非常经济有效的方法。
X-ray photoelectron spectroscopy (XPS) has been used to investigate the core-level electronic structures of glycine (G) and its peptides, including glycyl-glycine (GG), diglycyl-glycine (GGG), and polyglycine (poly-G), in their powder forms. Increasing the number of G units in the peptides does not change the locations of the respective C 1s, N 1s, and O 1s features corresponding to different functional groups: -COO(-), -NH(3)(+), >CH(2), and -CONH-. The electronic structures of the zwitterions of these molecules have been calculated as isolated molecules and as molecules in an aqueous environment under the periodic boundary conditions by quantum-mechanical and molecular mechanics methods. In the case of glycine zwitterion, the binding energies of the C 1s, N 1s, and O 1s XPS features are found to be in reasonable accord with the respective orbital energies obtained by Hartree-Fock self-consistent-field calculations, within the context of Koopmans' approximation. However, considerably worse agreement in the binding energies is found for the larger zwitterions (with the specific conformations considered in this work), indicating the need for higher-level calculations. The present work shows that optimizing the zwitterion in an aqueous environment under the periodic boundary conditions by molecular mechanics could be a very cost-effective approach for calculating the electronic structures of large, complex biomolecular systems.