溶解有机质主导水生环境中游离 DNA 碱基的光降解。
Dissolved organic matter dominating the photodegradation of free DNA bases in aquatic environments.
机构信息
CAS Key Laboratory of Urban Pollutant Conversion, Department of Applied Chemistry, University of Science and Technology of China, Hefei, 230026, China.
CAS Key Laboratory of Urban Pollutant Conversion, Department of Applied Chemistry, University of Science and Technology of China, Hefei, 230026, China.
出版信息
Water Res. 2020 Jul 15;179:115885. doi: 10.1016/j.watres.2020.115885. Epub 2020 May 1.
Free DNA bases are widely present in the environments, and can be utilized by bacteria for their nucleic acids synthesis or as nutrition sources. In sunlit natural waters, these free bases probably undergo photodegradation which would change the bioavailable bases contents. Though the photodegradation of DNA has been investigated, the photodegradation behaviors of free bases may be quite different from those of DNA-confined bases in consideration of their different chemical environments. Herein, the photodegradation of four free bases (guanine, adenine, thymine and cytosine) was investigated. Results show that direct photodegradation of free bases in phosphate buffer caused by UV was slow. However, the photodegradation of these free bases were greatly enhanced in dissolved organic matter (DOM) solution. In the presence of 10-50 mg/L DOM, the photodegradation rates of free bases were increased by 1.85-14.6 times compared to the controls without DOM. DOM could result in indirect photodegradation by producing hydroxyl radical (•OH) and singlet oxygen (O) under irradiation, and this indirect photodegradation enhanced and dominated the free bases photodegradation. The •OH was involved in all four bases photodegradation, while the O only participated in guanine photodegradation. In phosphate buffer, the fastest photodegradation bases were pyrimidine, however, guanine became the fastest photodegradation base in DOM solution due to the selective oxidation of guanine by O. In summary, DOM may be a determinant for free bases photodegradation in natural waters and thereby deeply influence free bases fates in aquatic environments.
游离碱基广泛存在于环境中，可被细菌用于合成核酸或作为营养源。在阳光充足的天然水中，这些游离碱基可能会经历光降解，从而改变生物可利用碱基的含量。虽然已经研究了 DNA 的光降解，但考虑到其不同的化学环境，游离碱基的光降解行为可能与 DNA 中碱基的光降解行为有很大的不同。在此，研究了四种游离碱基（鸟嘌呤、腺嘌呤、胸腺嘧啶和胞嘧啶）的光降解。结果表明，在磷酸盐缓冲液中，游离碱基的直接光降解（由 UV 引起）较慢。然而，在溶解有机物（DOM）溶液中，这些游离碱基的光降解大大增强。在 10-50mg/L DOM 的存在下，与没有 DOM 的对照相比，游离碱基的光降解速率提高了 1.85-14.6 倍。DOM 在光照下可以通过产生羟基自由基（•OH）和单线态氧（O）而导致间接光降解，这种间接光降解增强并主导了游离碱基的光降解。•OH 参与了所有四种碱基的光降解，而 O 仅参与了鸟嘌呤的光降解。在磷酸盐缓冲液中，光降解最快的碱基是嘧啶，然而，由于 O 对鸟嘌呤的选择性氧化，鸟嘌呤在 DOM 溶液中成为光降解最快的碱基。总之，DOM 可能是自然水中游离碱基光降解的决定因素，并因此深刻影响游离碱基在水生环境中的命运。
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