Center for Plant Aging Research, Institute for Basic Science, Daegu 42988, Republic of Korea.
Department of Chemistry, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2018 Jan 2;115(1):36-40. doi: 10.1073/pnas.1718559115. Epub 2017 Dec 18.
Aqueous microdroplets (<1.3 µm in diameter on average) containing 15 mM d-ribose, 15 mM phosphoric acid, and 5 mM of a nucleobase (uracil, adenine, cytosine, or hypoxanthine) are electrosprayed from a capillary at +5 kV into a mass spectrometer at room temperature and 1 atm pressure with 3 mM divalent magnesium ion (Mg) as a catalyst. Mass spectra show the formation of ribonucleosides that comprise a four-letter alphabet of RNA with a yield of 2.5% of uridine (U), 2.5% of adenosine (A), 0.7% of cytidine (C), and 1.7% of inosine (I) during the flight time of ∼50 µs. In the case of uridine, no catalyst is required. An aqueous solution containing guanine cannot be generated under the same conditions given the extreme insolubility of guanine in water. However, inosine can base pair with cytidine and thus substitute for guanosine. Thus, a full set of ribonucleosides to generate the purine-pyrimidine base pairs A-U and I-C are spontaneously generated in aqueous microdroplets under similar mild conditions.
水微滴（平均直径<1.3 µm）中含有 15 mM d-核糖、15 mM 磷酸和 5 mM 碱基（尿嘧啶、腺嘌呤、胞嘧啶或次黄嘌呤），在室温下和 1 个大气压下，用 3 mM 二价镁离子（Mg）作为催化剂，从毛细管中以+5 kV 的电压电喷雾到质谱仪中。质谱显示核糖核苷的形成，核糖核苷由 RNA 的四个字母组成，尿嘧啶（U）的产率为 2.5%，腺嘌呤（A）的产率为 2.5%，胞嘧啶（C）的产率为 0.7%，次黄嘌呤（I）的产率为 1.7%，飞行时间约为 50 µs。在尿嘧啶的情况下，不需要催化剂。由于鸟嘌呤在水中的极端不溶性，在相同条件下不能生成含有鸟嘌呤的水溶液。然而，次黄嘌呤可以与胞嘧啶碱基配对，从而替代鸟嘌呤。因此，在类似的温和条件下，水微滴中可以自发生成一套完整的核糖核苷，以生成嘌呤-嘧啶碱基对 A-U 和 I-C。
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