Faculty of Health Sciences, University of SS Cyril and Methodius, Trnava 91701, Slovakia.
Faculty of Natural Sciences, University of SS Cyril and Methodius, Trnava 91701, Slovakia.
J Phys Chem A. 2024 Sep 26;128(38):8088-8095. doi: 10.1021/acs.jpca.4c04538. Epub 2024 Sep 12.
Four branched-chain aliphatic α-amino acids─α-alanine, valine, leucine, and isoleucine (-)─were investigated by quantum-chemical calculations in water as a solvent by two methods. The B3LYP variant of DFT calculations was used to obtain the electronic structure and molecular descriptors of these species in their canonical amino acid form as well as the related zwitterionic form in three oxidation states (cation, neutral molecule, and anion). A total of 24 species were subjected to full geometry optimization and complete vibration analysis. Quantities related to ionization or affinity processes were evaluated under adiabatic conditions. The calculated standard reaction Gibbs energy facilitates evaluation of the absolute oxidation and reduction potential. The absolute reduction potential correlates with the electrophilicity index, and the absolute oxidation potential correlates with the adiabatic ionization energy. This finding makes it possible to skip the tedious vibrational analysis and use electronic properties to estimate the redox potentials. The molecular descriptors were compared with the calculated properties of four linear amino acids (glycine, β-alanine, GABA, and DAVA). Parallel calculations using the DLPNO-CCSD(T) method gave analogous results for 24 species. The absolute oxidation potential was related to the antioxidant activity index, which showed only a moderate antioxidant activity of -.
四种支链脂肪族α-氨基酸——丙氨酸、缬氨酸、亮氨酸和异亮氨酸(-)——在水溶剂中通过两种方法进行了量子化学计算。采用 DFT 计算的 B3LYP 变体获得了这些物质在其经典氨基酸形式以及三种氧化态(阳离子、中性分子和阴离子)下相关两性离子形式的电子结构和分子描述符。总共 24 种物质进行了全几何优化和完全振动分析。在绝热条件下评估了与电离或亲和过程相关的量。计算的标准反应吉布斯自由能有助于评估绝对氧化还原电位。绝对还原电位与亲电指数相关，绝对氧化电位与绝热电离能相关。这一发现使得可以跳过繁琐的振动分析并使用电子性质来估计氧化还原电位。将分子描述符与四种线性氨基酸(甘氨酸、β-丙氨酸、GABA 和 DAVA)的计算性质进行了比较。使用 DLPNO-CCSD(T)方法进行的平行计算得到了 24 种物质的类似结果。绝对氧化电位与抗氧化活性指数相关，表明只有-的中等抗氧化活性。
