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Efficient Quantum-Chemical Calculations of Acid Dissociation Constants from Free-Energy Relationships
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2021-06-18 , DOI: 10.1021/acs.jpca.1c03463
Philipp Pracht 1 , Stefan Grimme 1
Affiliation  

The calculation of acid dissociation constants (pKa) is an important task in computational chemistry and chemoinformatics. Theoretically and with minimal empiricism, this is possible from computed acid dissociation free energies via so-called linear free-energy relationships. In this study some modifications are introduced to the latter, providing a straightforward, broadly applicable protocol with an adjustable degree of sophistication for quantum chemistry-based calculations of pKa in water. It targets a wide pKa range (∼70 units) and medium-sized, flexible molecules. Herein, a focus is set on the recently published r2SCAN-3c and related efficient composite density functionals and the semiempirical GFN2–xTB method, including a newly introduced energy correction for heterolytic dissociation, both in combination with implicit solvation models. The performance is evaluated in comparison with experimental data, showing mean errors often smaller than a targeted 1 pKa unit accuracy. Larger deviations are observed only upon inclusion of challenging highly negative (<−5) or positive (>15) pKa values. Among all those tested, it is found that B97-3c is the best performing functional, although rather independently of the density functional theory (DFT) method used; low root-mean-square errors of 0.8–1.0 pKa units for typical drugs are obtained. For optimal performance, it is recommended to employ DFT functional specific free-energy relationship parameters. Additionally, a significant conformational dependence of the pKa values is revealed and quantified for some nonrigid drug molecules.

中文翻译:

从自由能关系中有效地量子化学计算酸解离常数

酸解离常数 (p K a ) 的计算是计算化学和化学信息学中的一项重要任务。从理论上和最小的经验主义,这可以通过所谓的线性自由能关系从计算的酸解离自由能中实现。在这项研究中,对后者进行了一些修改,为基于量子化学的水中p K a计算提供了一个简单、广泛适用的协议,其复杂程度可调节。它针对较宽的 p K a范围(~70 个单位)和中等大小的柔性分子。在此,重点放在最近发表的 r 2SCAN-3c 和相关的高效复合密度泛函和半经验 GFN2-xTB 方法,包括新引入的异溶解离能量校正,两者都与隐式溶剂化模型相结合。与实验数据相比较的性能进行评价时,显示平均误差往往比目标1个p时ķ一个单元的精度。只有在包含具有挑战性的高度负 (<-5) 或正 (>15) p K a值时,才会观察到更大的偏差。在所有测试中,发现 B97-3c 是性能最好的泛函,尽管与所使用的密度泛函理论 (DFT) 方法无关;0.8–1.0 p K a 的低均方根误差获得典型药物的单位。为了获得最佳性能,建议使用 DFT 函数特定的自由能关系参数。此外,揭示并量化了一些非刚性药物分子的 p K a值的显着构象依赖性。
更新日期:2021-07-01
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