DNA alkylation is caused by long-term exposure of cells to the environmental and endogenous alkylating agents, which can also lead to DNA mutations and therefore trigger some cancers. Since O4-methylthymidine (O4-meT), mismatched with guanine (G), is the most common but not easily repaired alkylated nucleoside, monitoring O4-meT can help to effectively reduce the occurrence of carcinogenesis. In this work, the modified G-analogues are selected as the fluorescence probe to monitor the existence of O4-meT according to its pairing characteristics. The photo-physical properties of considered G-analogues formed by ring expansion or addition of fluorophores were studied in detail. It is found that, compared with natural G, the absorption peaks of these fluorescence analogues are red-shifted (>55 nm) and the luminescence is enhanced by π-conjugation. Especially, the xG has a large Stokes shift (65 nm) with fluorescence insensitive to natural cytosine (C) and retains efficient emission after pairing, while it is sensitive to O4-meT and the quenching phenomenon occurs due to the excited state intermolecular charge transfer. Accordingly, the xG can be used as a fluorescent probe to identify the O4-meT in solution. In addition, the direct use of deoxyguanine fluorescent analogue for monitoring O4-meT was evaluated by the effects of ligating deoxyribose on absorption and fluorescence emission.

DNA烷基化是由细胞长期暴露于环境和内源性烷化剂引起的，这也会导致DNA突变，从而引发某些癌症。由于与鸟嘌呤 (G) 不匹配的 O4-甲基胸苷 (O4-meT) 是最常见但不易修复的烷基化核苷，监测 O4-meT 有助于有效减少癌变的发生。在这项工作中，根据其配对特征，选择修饰的 G 类似物作为荧光探针来监测 O4-meT 的存在。详细研究了通过扩环或添加荧光团形成的所考虑的 G 类似物的光物理性质。结果发现，与天然 G 相比，这些荧光类似物的吸收峰发生红移 (>55 nm)，并且发光因 π 共轭而增强。特别是，xG 具有较大的斯托克斯位移 (65 nm)，荧光对天然胞嘧啶 (C) 不敏感，配对后仍保持有效发射，而对 O4-meT 敏感，并且由于激发态分子间电荷转移而发生猝灭现象. 因此，xG 可用作荧光探针来识别溶液中的 O4-meT。此外，通过连接脱氧核糖对吸收和荧光发射的影响，评估了直接使用脱氧鸟嘌呤荧光类似物监测 O4-meT。xG 可用作荧光探针来识别溶液中的 O4-meT。此外，通过连接脱氧核糖对吸收和荧光发射的影响，评估了直接使用脱氧鸟嘌呤荧光类似物监测 O4-meT。xG 可用作荧光探针来识别溶液中的 O4-meT。此外，通过连接脱氧核糖对吸收和荧光发射的影响，评估了直接使用脱氧鸟嘌呤荧光类似物监测 O4-meT。