Departamento de Química Fundamental, Universidade Federal de Pernambuco, Recife, Pernambuco, 50740-540, Brazil.
Unidade Acadêmica de Física e Matemática - UAFM, Centro de Educação E Saúde - CES, Universidade Federal de Campina Grande - UFCG, Sítio Olho d'Agua da Bica S/N, Cuité, Paraíba, 58175-000, Brazil.
J Mol Model. 2023 Mar 11;29(4):94. doi: 10.1007/s00894-023-05500-z.
Hydrogen bonds (HB) influence the conformational preferences of biomolecules and their optical and electronic properties. The directional interaction of molecules of water can be a prototype to understand the effects of HBs on biomolecules. Among the neurotransmitters (NT), L-aspartic acid (ASP) stands out due to its importance in health and as a precursor of several biomolecules. As it presents different functional groups and readily forms inter- and intramolecular HBs, ASP can be considered a prototype for understanding the behavior of NTs when interacting by HB with other substances. Although several theoretical studies have been performed in the past on isolated ASP and its formed complexes with water, both in gas and liquid phases, using DFT and TD-DFT formalisms, these works did not perform large basis set calculations or study electronic transitions of ASP-water complexes. We investigated the HB interactions in complexes of ASP and water molecules. The results show that the interactions between the carboxylic groups of ASP with water molecules, forming cyclic structures with two HBs, lead to more stable and less polar complexes than other conformers formed between water and the NH group. It was observed that there is a relationship between the deviation in the UV-Vis absorption band of the ASP and the interactions of water with the HOMO and LUMO orbitals with the stabilization/destabilization of the S state to the S of the complexes. However, in some cases, such as 1:1 complex ASP-W2, this analysis may be inaccurate due to small changes in ΔE.
We studied the landscapes of the ground state surface of different conformers of isolated L-ASP and the L-ASP-(HO) complexes (n = 1 and 2) using the DFT formalism, with the B3LYP functional, and six different basis sets: 6-31 + + G(d,p), 6-311 + + G(d,p), D95 + + (d,p), D95V + + (d,p), cc-pVDZ, and, cc-pVTZ basis sets. The cc-pVTZ basis set provides the minimum energy of all conformers, and therefore, we performed the analysis with this basis set. We evaluated the stabilization of the ASP and complexes using the minimum ground state energy, corrected by the zero point energy and the interaction energy between the ASP and the water molecules. We also calculated the vertical electronic transitions S ← S, and their properties using the TD-DFT formalism at B3LYP/cc-pVTZ level with the optimized geometries for S state with the same basis set. For the analysis of the vertical transitions of isolated ASP and the ASP-(HO) complexes, we calculated the electrostatic energy in the S and S states. We performed the calculations with the Gaussian 09 software package. We used the VMD software package to visualize the geometries and shapes of the molecule and complexes.
氢键（HB）影响生物分子的构象偏好及其光学和电子性质。水分子的定向相互作用可以作为理解 HB 对生物分子影响的原型。在神经递质（NT）中，L-天冬氨酸（ASP）因其在健康中的重要性以及作为几种生物分子前体而引人注目。由于其具有不同的官能团且易于形成分子内和分子间氢键，因此 ASP 可以被视为理解 NT 与其他物质通过氢键相互作用时行为的原型。尽管过去已经使用 DFT 和 TD-DFT 形式理论研究了 ASP 及其在气相和液相中与水形成的复合物，但这些工作没有进行大基组计算或研究 ASP-水复合物的电子跃迁。我们研究了 ASP 和水分子复合物中的氢键相互作用。结果表明，ASP 的羧酸基团与水分子形成具有两个氢键的环状结构，导致比与 NH 基团形成的其他构象更稳定和极性更小的复合物。观察到 ASP 的紫外-可见吸收带的偏移与水与 HOMO 和 LUMO 轨道的相互作用之间存在关系，这与复合物的 S 态的稳定/失稳有关。然而，在某些情况下，例如 1:1 的 ASP-W2 复合物，由于 ΔE 变化较小，这种分析可能不准确。
我们使用 DFT 形式理论，B3LYP 函数和六个不同的基组：6-31++G(d,p)、6-311++G(d,p)、D95++(d,p)、D95V++(d,p)、cc-pVDZ 和 cc-pVTZ 基组，研究了不同构象的游离 L-ASP 和 L-ASP-(HO)复合物（n=1 和 2）的基态表面的地形。cc-pVTZ 基组提供了所有构象的最低能量，因此，我们使用该基组进行了分析。我们使用零能校正和 ASP 与水分子之间的相互作用能来评估 ASP 和复合物的稳定化。我们还使用 B3LYP/cc-pVTZ 水平的 TD-DFT 形式理论计算了 S→S 的垂直电子跃迁及其性质，并使用相同基组的 S 态优化几何形状进行了计算。对于游离 ASP 和 ASP-(HO)复合物的垂直跃迁分析，我们计算了 S 和 S 态的静电能。我们使用 Gaussian 09 软件包进行了计算。我们使用 VMD 软件包可视化分子和复合物的几何形状和形状。
