The high stability of the DNA bases after UV photoexcitation is generally ascribed to their intrinsic ability to dissipate the supplied electronic energy on ultrafast time scales. The sugar-phosphate backbone of the related nucleosides and nucleotides may modulate the efficiency of these relaxation processes by hydrogen bonding and/or intramolecular energy transfer. To elucidate these effects, we performed a comparative study of the excited-state lifetimes of 9H-adenine, its nucleosides adenosine and deoxyadenosine, and its nucleotides adenosine monophosphate and deoxyadenosine monophosphate by transient electronic absorption spectroscopy under otherwise constant experimental conditions. All five adenine derivatives were found to exhibit virtually identical spectro-temporal behavior with uniform excited-state lifetimes of ${\tau }_1=0.19\pm 0.03$ ps and ${\tau }_2=0.45\pm 0.05$ ps. The results support a common deactivation mechanism within the adenine unit that leaves the DNA sugar-phosphate backbone groups idle.

紫外光激发后，DNA碱基的高稳定性通常归因于其以超快的时间尺度消散所供应的电子能量的内在能力。相关核苷和核苷酸的糖磷酸主链可通过氢键和/或分子内能量转移来调节这些弛豫过程的效率。为了阐明这些影响，我们通过瞬态电子吸收光谱在其他恒定的实验条件下，对9H-腺嘌呤，其核苷腺苷和脱氧腺苷以及其核苷酸腺苷单磷酸和脱氧腺苷单磷酸的激发态寿命进行了比较研究。发现所有五个腺嘌呤衍生物均表现出几乎相同的光谱时态行为，且激发态寿命均匀。${\tau }_{\mathrm{1个}}=0.19\pm 0.03$ ps和 ${\tau }_{\mathrm{2个}}=0.45\pm 0.05$ ps。结果支持腺嘌呤单元内的常见失活机制，使DNA糖磷酸主链基团保持闲置状态。