Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.
Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, Ontario K7L 3N6, Canada.
Spectrochim Acta A Mol Biomol Spectrosc. 2017 Apr 5;176:1-7. doi: 10.1016/j.saa.2016.12.012. Epub 2016 Dec 15.
3-Methyladenine and 7-methyladenine are biomarkers of DNA damage from exposure to methylating agents. For example, the concentration of 3-methyladenine increases significantly in the urine of cigarette smokers. Surface-enhanced Raman spectroscopy (SERS) has shown much potential for detection of biomolecules, including DNA. Much work has been dedicated to the canonical nucleobases, with comparatively fewer investigations of modified DNA and modified DNA nucleobases. Herein, Raman spectroscopy and SERS are used to examine the adsorption orientations of 3-methyladenine and 7-methyladenine on Ag nanoparticles. Density functional theory (DFT) calculations at the B3LYP level are used to support the conclusions via simulated spectra of the nucleobases and of Ag/nucleobase complexes. The results herein show that 7-methyladenine adsorbs upright via its N3 and N9 atoms side, similarly to adenine. 3-Methyladenine adsorbs in a very tilted or flat orientation on the Ag nanoparticles. These findings will be useful for future SERS or other nanoparticle-based bioanalytical assays for detection of these methyladenines or other modified nucleobases.
3-甲基腺嘌呤和 7-甲基腺嘌呤是暴露于甲基化试剂导致 DNA 损伤的生物标志物。例如，吸烟的人的尿液中 3-甲基腺嘌呤的浓度显著增加。表面增强拉曼光谱（SERS）已显示出对生物分子（包括 DNA）检测的巨大潜力。大量工作致力于研究典型的核碱基，而对修饰的 DNA 和修饰的 DNA 核碱基的研究相对较少。本文利用拉曼光谱和 SERS 研究了 3-甲基腺嘌呤和 7-甲基腺嘌呤在银纳米粒子上的吸附取向。在 B3LYP 水平上使用密度泛函理论（DFT）计算通过核碱基和 Ag/核碱基复合物的模拟光谱来支持结论。本文的结果表明，7-甲基腺嘌呤通过其 N3 和 N9 原子侧面垂直吸附，类似于腺嘌呤。3-甲基腺嘌呤在银纳米粒子上以非常倾斜或平面的取向吸附。这些发现将有助于未来基于 SERS 或其他基于纳米粒子的生物分析测定法来检测这些甲基腺嘌呤或其他修饰的核碱基。
