In order to establish an RNA world on early Earth, the nucleotides must form polymers through chemical rather than biochemical reactions. The polymerization products must be long enough to perform catalytic functions, including self-replication, and to preserve genetic information. These functions depend not only on the length of the polymers, but also on their sequences. To date, studies of abiotic RNA polymerization generally have focused on routes to polymerization of a single nucleotide and lengths of the homopolymer products. Less work has been done the selectivity of the reaction toward incorporation of some nucleotides over others in nucleotide mixtures. Such information is an essential step toward understanding the chemical evolution of RNA. To address this question, in the present work RNA polymerization reactions were performed in the presence of montmorillonite clay catalyst. The nucleotides included the monophosphates of adenosine, cytosine, guanosine, uridine and inosine. Experiments included reactions of mixtures of an imidazole-activated nucleotide (ImpX) with one or more unactivated nucleotides (XMP), of two or more ImpX, and of XMP that were activated in situ in the polymerization reaction itself. The reaction products were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify the lengths and nucleotide compositions of the polymerization products. The results show that the extent of polymerization, the degree of heteropolymerization vs. homopolymerization, and the composition of the polymeric products all vary among the different nucleotides and depend upon which nucleotides and how many different nucleotides are present in the mixture.

中文翻译：

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非生物RNA聚合反应中的核苷酸选择性。

为了在地球早期建立一个RNA世界，核苷酸必须通过化学而非生化反应形成聚合物。聚合产物必须足够长以执行催化功能，包括自我复制并保存遗传信息。这些功能不仅取决于聚合物的长度，而且取决于它们的序列。迄今为止，非生物RNA聚合的研究通常集中在单核苷酸的聚合途径和均聚物产物的长度上。相对于在核苷酸混合物中掺入某些核苷酸的反应，对反应的选择性进行的工作较少。此类信息是理解RNA化学进化的重要步骤。为了解决这个问题，在本工作中，RNA聚合反应在蒙脱石粘土催化剂的存在下进行。核苷酸包括腺苷，胞嘧啶，鸟苷，尿苷和肌苷的单磷酸酯。实验包括在聚合反应本身中就地活化的咪唑活化核苷酸（ImpX）与一个或多个未活化核苷酸（XMP），两个或多个ImpX和XMP的混合物反应。使用基质辅助激光解吸/电离飞行时间质谱（MALDI-TOF MS）分析反应产物，以鉴定聚合产物的长度和核苷酸组成。结果表明，聚合程度，杂聚合度与均聚度，