The emergence of evermore complex entities from prebiotic building blocks is a key aspect of origins of life research. The RNA-world hypothesis posits that RNA oligomers known as ribozymes acted as the first self-replicating entities. However, the mechanisms governing the self-assembly of complex informational polymers from the shortest prebiotic building blocks were unclear. One open issue concerns the relation between concentration and oligonucleotide length, usually assumed to be exponentially decreasing. Here, we show that a competition of timescales in the self-assembly of informational polymers by templated ligation generically leads to nonmonotonic strand-length distributions with two distinct length scales. The first length scale characterizes the onset of a strongly nonequilibrium regime and is visible as a local minimum. Dynamically, this regime is governed by extension cascades, where the elongation of a “primer” with a short building block is more likely than its dehybridization. The second length scale appears as a local concentration maximum and reflects a balance between degradation and dehybridization of completely hybridized double strands in a heterocatalytic extension-reassembly process. Analytical arguments and extensive numerical simulations within a sequence-independent model allowed us to predict and control these emergent length scales. Nonmonotonic strand-length distributions confirming our theory were obtained in thermocycler experiments using random DNA sequences from a binary alphabet. Our work emphasizes the role of structure-forming processes already for the earliest stages of prebiotic evolution. The accumulation of strands with a typical length reveals a possible starting point for higher-order self-organization events that ultimately lead to a self-replicating, evolving system.

中文翻译：

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通过模板连接自组装信息聚合物

从益生元构建块中出现越来越复杂的实体是生命起源研究的一个关键方面。RNA 世界假说假定称为核酶的 RNA 寡聚体充当第一个自我复制实体。然而，从最短的益生元构建块中控制复杂信息聚合物自组装的机制尚不清楚。一个悬而未决的问题涉及浓度和寡核苷酸长度之间的关系，通常假设为呈指数下降。在这里，我们展示了通过模板化连接在信息聚合物自组装中的时间尺度竞争通常会导致具有两个不同长度尺度的非单调链长度分布。第一个长度尺度表征了强烈非平衡状态的开始，并且作为局部最小值可见。动态地，该机制受延伸级联控制，其中具有短结构单元的“引物”的延伸比其去杂交更有可能。第二个长度尺度表现为局部浓度最大值，反映了杂催化延伸-重组过程中完全杂交双链的降解和去杂交之间的平衡。序列独立模型中的分析论证和广泛的数值模拟使我们能够预测和控制这些新兴的长度尺度。证实我们的理论的非单调链长度分布是在热循环仪实验中使用二进制字母表中的随机 DNA 序列获得的。我们的工作强调了结构形成过程在益生元进化最早阶段的作用。