A previously proposed synthesis of pyrimidine ribonucleotides makes use of ultraviolet (UV) light to convert β-d-ribocytidine-2′,3′-cyclic phosphate to β-d-ribouridine-2′,3′-cyclic phosphate, while simultaneously selectively degrading synthetic byproducts. Past studies of the photochemical reactions of pyrimidines have employed mercury arc lamps, characterized by narrowband emission centered at 254 nm, which is not representative of the UV environment of the early Earth. To further assess this process under more realistic circumstances, we investigated the wavelength dependence of the UV-driven conversion of β-d-ribocytidine-2′,3′-cyclic phosphate to β-d-ribouridine-2′,3′-cyclic phosphate. We used constraints provided by planetary environments to assess the implications for pyrimidine nucleotides on the early Earth. We found that the wavelengths of light (255–285 nm) that most efficiently drive the deamination of β-d-ribocytidine-2′,3′-cyclic phosphate to β-d-ribouridine-2′,3′-cyclic phosphate are accessible on planetary surfaces such as those of the Hadean-Archaean Earth for CO₂-N₂-dominated atmospheres. However, continued irradiation could eventually lead to low levels of ribocytidine in a low-temperature, highly irradiated environment, if production rates are slow.

中文翻译：

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行星条件下胞苷核糖核苷酸的紫外线驱动脱氨。

先前提出的嘧啶核糖核苷酸的合成利用紫外线 (UV) 光将 β- d-核糖胞苷-2',3'-环状磷酸盐转化为 β- d-核糖胞苷-2',3'-环状磷酸盐，同时选择性地降解合成副产品。过去对嘧啶的光化学反应的研究使用了汞弧灯，其特征在于以 254 nm 为中心的窄带发射，这并不代表早期地球的紫外线环境。为了在更实际的情况下进一步评估这一过程，我们研究了紫外驱动的 β-d-核糖胞苷-2',3'-环状磷酸盐转化为 β- d的波长依赖性。-ribouridine-2',3'-环状磷酸盐。我们使用行星环境提供的限制来评估早期地球上嘧啶核苷酸的影响。我们发现最有效地驱动 β-d-核糖胞苷-2',3'-环磷酸酯脱氨为 β-d-核糖胞苷-2',3'-环磷酸酯的光波长 ( 255–285 nm )是在诸如冥王星-太古代地球等行星表面上可接触到以 CO ₂ -N ₂为主的大气。然而，如果生产速度缓慢，在低温、高度辐照的环境中，持续辐照最终可能导致核糖胞苷水平降低。