College of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, Liaoning, China; Qinhuangdao key laboratory of water-saving pollution control and ecological restoration, College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, 066004, Hebei, China.
Qinhuangdao key laboratory of water-saving pollution control and ecological restoration, College of Resources and Materials, Northeastern University at Qinhuangdao, Qinhuangdao, 066004, Hebei, China.
Sci Total Environ. 2020 Jul 15;726:138432. doi: 10.1016/j.scitotenv.2020.138432. Epub 2020 Apr 5.
Tetracycline is a type of broad-spectrum, naturally occurring antibiotic that leads to several side effects, such as affecting intestinal flora and increase in bacterial resistance. The affinity of tetracycline for abiotic and biotic surfaces and metal ions is closely related to its deprotonation state and charge distribution; however, its deprotonation-protonation property remains unclear. In this study, the hydrolysis of tetracycline was investigated by combining experiments with quantum-chemical calculations. The molecular structure of the probable deprotonation states were optimized by quantum-chemical calculations, and the corresponding absorbance spectra were predicted based on frontier molecular orbital (FMO) theory. The absorbance spectra showed structure-specific features at the different deprotonation states. In addition, changes in tetracycline absorbance spectra in the pH range of 2.00-12.00 was examined by spectroscopic titration. The deprotonation was found to proceed in the order of site 3, 4, 12, and 10, which was identified by comparing the quantum-chemical calculations and experimental differential absorbance spectra (DAS). The results in this study are of great significance for further studies of the transport and fate of tetracycline in the environment.
四环素是一种广谱、天然存在的抗生素，会导致多种副作用，如影响肠道菌群和增加细菌耐药性。四环素与非生物和生物表面以及金属离子的亲和力与其去质子化状态和电荷分布密切相关，但它的去质子化-质子化性质尚不清楚。在这项研究中，通过结合实验和量子化学计算来研究四环素的水解。通过量子化学计算对可能的去质子化状态的分子结构进行了优化，并根据前线分子轨道（FMO）理论预测了相应的吸收光谱。吸收光谱在不同的去质子化状态下表现出结构特异性特征。此外，通过光谱滴定法研究了四环素在 pH 值为 2.00-12.00 范围内的吸收光谱变化。通过比较量子化学计算和实验差分吸收光谱（DAS），确定了去质子化的顺序为 3 位、4 位、12 位和 10 位。本研究的结果对进一步研究四环素在环境中的迁移和归宿具有重要意义。
