Ultrafast dynamics of the NH bond and its significance towards the photoresistive mechanism of nucleic bases and base-pairs

吸收光的过程在我们的日常生活中扮演着不可或缺的角色。大自然精心挑选了我们的分子构件，以便绕过紫外线辐射的潜在破坏性影响。腺嘌呤、胸腺嘧啶、鸟嘌呤和胞嘧啶是构成DNA遗传密码的基础，它们很容易吸收紫外线辐射。一旦被吸收，这种能量就会非常有效地通过无害的分子弛豫途径扩散，从而降低分子击穿的风险，从而减少光化学损害。这些光阻路径的时间尺度必须非常快，才能有效地与有害路径竞争。然而，越来越清楚的是，尽管用激光进行的超快测量揭示了非常快的弛豫路径，但需要更精细的实验来测试越来越复杂的计算，这些计算模拟了这些路径背后的理论。这里描述的工作包括两个方面：第一，建立一个实验装置，允许将核碱基引入到孤立的分子环境中。其次，用超快激光脉冲序列询问这些分子，以便我们识别这些路径并完全表征它们。在观察了分离的核碱基之后，实验将扩展到更现实的情况，如核碱基对，并试图理解为什么大自然选择了我们遗传密码的核碱基以如此独特的方式配对。例如，碱基对是否表现出比单个核碱基更强的耐光性？这些研究的结果将使我们能够开发出一些管理DNA碱基和碱基对中发生的光化学过程的基本原理，并验证这些系统中已有的理论模型。这些成果还将适用于生物化学和生物物理学等领域，说明这项工作的跨学科性质。所要求的大部分资金用于购买必要的设备，以帮助启动国际和平研究所的研究事业。也为研究生申请资金，尽管不寻求博士后支持，因为PI拥有皇家学会大学奖学金，并将担任博士后研究员的角色。该装置本身将远远超过提议的时间尺度，为PI的研究提供连续性，并将化学系带入英国实验超快化学动力学的前沿。

Processes which involve the absorption of light play an integral role in our day-to-day lives. Nature has carefully chosen our molecular building blocks so that the potentially devastating effects of ultraviolet radiation are by-passed. The nucleic bases adenine, thymine, guanine and cytosine, which constitute the building blocks of our genetic code, DNA, absorb ultraviolet radiation very readily. Once absorbed, this energy is very efficiently diffused through harmless molecular relaxation pathways reducing the risk of molecular breakdown and therefore photochemical damage. The timescales of these photoresistive pathways must be very fast for them to compete effectively with the detrimental paths. It is becoming increasingly clear however that, although ultrafast measurements with lasers reveal very fast relaxation pathways, more refined experiments are required to test the ever increasingly sophisticated calculations that model the theory behind these pathways. The work described here is two-fold: Firstly, to build an experimental apparatus which allows introduction of the nucleic bases into an isolated molecular environment. Secondly, interrogate these molecules with sequences of ultrafast laser pulses so that we identify these pathways and completely characterize them. Having looked at the isolated nucleic bases, the experiments will then be extended to look at a more realistic scenario such as a nucleic base-pair and try to understand why nature has chosen the nucleic bases of our genetic code to be paired in such a unique way. For instance, do base-pairs show more photoresistance than the individual nucleic bases? The results of these studies will allow us to develop some basic principles governing the photochemical processes occurring in DNA bases and base-pairs and validate the theoretical models already present on these systems. The results will also lend themselves to fields such as biochemistry and biophysics, illustrating the interdisciplinary nature of this work. The majority of the funds requested are on essential equipment to help start-up the research career of the PI. Funds are also requested for a research student although postdoctoral support is not sought as the PI holds a Royal Society University Fellowship and will take the role of the postdoctoral researcher. The apparatus itself will far exceed the timescale of the proposal, provide continuity to the PI's research and bring the Department of Chemistry to the forefront of U.K. experimental ultrafast chemical dynamics.