Environmental DNA (eDNA), i.e., DNA found in the environment, can interact with various geochemical surfaces, yet little is known about these interactions. Mineral surfaces may alter the structure, stability, and reactivity of eDNA, impacting the cycling of genetic information and the reliability of eDNA-based detection tools. Understanding how eDNA interacts with surfaces is crucial for predicting its fate in the environment. In this study, we examined the surface interaction and stability of herring testes DNA, a model system for eDNA, on two common iron oxide phases present in the environment: α-FeOOH (goethite) and α-Fe₂O₃ (hematite). Utilizing spectroscopic probes, including attenuated total reflection Fourier-transform infrared (ATR-FTIR) and UV–vis spectroscopy, we quantified the DNA adsorption capacity at pH 5 and determined its secondary structure. DNA adsorbed irreversibly at pH 5 and 25 °C, primarily through its phosphate groups, and retained the solution-phase B-form structure. However, the infrared data also indicated some distortion of the B-form likely due to additional interactions between nitrogenous bases when adsorbed on the α-Fe₂O₃ particle surfaces. The distortion in the double helical structure of adsorbed DNA on α-Fe₂O₃ led to a lower melting temperature (T_m) of 60 °C compared to 70 °C for DNA in solution. In contrast, DNA adsorbed on α-FeOOH melted at higher temperatures relative to solution-phase DNA and in two distinct phases. Upon testing adsorbed DNA stability at higher pH values, there were distinct differences between the two iron oxide phases. For α-FeOOH, nearly 50% of the DNA desorbed from the surface when the solution pH changed from 5 to 8, while less than 5% desorbed from α-Fe₂O₃ under the same conditions. Overall, these findings underscore the importance of mineral-specific eDNA–surface interactions and their role in adsorbed eDNA stability, in terms of DNA melting and the impact of solution-phase pH changes.

中文翻译：

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表面吸附对 DNA 结构和稳定性的影响：对环境 DNA 与氧化铁表面相互作用的影响


环境 DNA （eDNA），即在环境中发现的 DNA，可以与各种地球化学表面相互作用，但对这些相互作用知之甚少。矿物表面可能会改变 eDNA 的结构、稳定性和反应性，从而影响遗传信息的循环和基于 eDNA 的检测工具的可靠性。了解 eDNA 如何与表面相互作用对于预测其在环境中的命运至关重要。在这项研究中，我们检查了鲱鱼睾丸 DNA（一种 eDNA 模型系统）在环境中存在的两种常见氧化铁相上的表面相互作用和稳定性：α-FeOOH（针铁矿）和 α-Fe₂O₃（赤铁矿）。利用光谱探针，包括衰减全反射傅里叶变换红外 （ATR-FTIR） 和紫外-可见光谱，我们量化了 pH 5 时的 DNA 吸附能力并确定了其二级结构。DNA 在 pH 5 和 25 °C 下主要通过其磷酸基团不可逆地吸附，并保留了液相 B 型结构。然而，红外数据也表明 B 型发生了一些变形，这可能是由于吸附在 α-Fe₂O₃ 颗粒表面上时含氮碱之间的额外相互作用造成的。α-Fe₂O₃ 上吸附的 DNA 的双螺旋结构发生扭曲，导致 DNA 的熔解温度 （T m） 较低，为 60 °C，而溶液中 DNA 的熔解温度 （T_m） 为 70 °C。相比之下，吸附在 α-FeOOH 上的 DNA 在相对于液相 DNA 的更高温度下熔解，并且以两个不同的相熔解。在较高 pH 值下测试吸附的 DNA 稳定性后，两种氧化铁相之间存在明显差异。 对于 α-FeOOH，当溶液 pH 值从 5 变为 8 时，近 50% 的 DNA 从表面解吸，而在相同条件下，只有不到 5% 的 DNA 从 α-Fe₂O₃ 中解吸。总体而言，这些发现强调了矿物特异性 eDNA-表面相互作用的重要性及其在吸附 eDNA 稳定性中的作用，包括 DNA 熔解和液相 pH 变化的影响。