School of Chemistry and EaStCHEM , University of St Andrews , North Haugh , St Andrews , Fife KY16 9ST , U.K.
J Am Chem Soc. 2019 Sep 4;141(35):13905-13913. doi: 10.1021/jacs.9b06697. Epub 2019 Aug 26.
The emergence of collections of simple chemical entities that create self-sustaining reaction networks, embedding replication and catalysis, is cited as a potential mechanism for the appearance on the early Earth of systems that satisfy minimal definitions of life. In this work, a functional reaction network that creates and maintains a set of privileged replicator structures through auto- and cross-catalyzed reaction cycles is created from the pairwise combinations of four reagents. We show that the addition of individual preformed templates to this network, representing instructions to synthesize a specific replicator, induces changes in the output composition of the system that represent a network-level response. Further, we establish through sets of serial transfer experiments that the catalytic connections that exist between the four replicators in this network and the system-level behavior thereby encoded impose limits on the compositional variability that can be induced by repeated exposure to instructional inputs, in the form of preformed templates, to the system. The origin of this persistence is traced through kinetic simulations to the properties and inter-relationships between the critical ternary complexes formed by the auto- and crosscatalytic templates. These results demonstrate that in an environment where there is no continuous selection pressure the network connectivity, described by the catalytic relationships and system-level interactions between the replicators, is persistent, thereby limiting the ability of this network to adapt and evolve.
简单化学实体集合的出现，这些实体能够创建自我维持的反应网络，嵌入复制和催化作用，被认为是早期地球上满足生命最低定义的系统出现的潜在机制。在这项工作中，通过四个试剂的成对组合创建了一个功能反应网络，该网络通过自动和交叉催化反应循环创建和维持一组特权复制结构。我们表明，将单个预形成的模板添加到该网络中，代表合成特定复制子的指令，会导致系统输出组成发生变化，代表网络级响应。此外，我们通过一系列连续转移实验建立了这样一个事实，即在这个网络中四个复制子之间的催化连接以及由此编码的系统级行为，对可以通过重复暴露于指令输入（以预形成的模板形式）到系统中诱导的组成可变性施加限制。这种持久性的起源可以通过动力学模拟追溯到自动和交叉催化模板形成的关键三元复合物的性质和相互关系。这些结果表明，在没有连续选择压力的环境中，网络连接性（由复制子之间的催化关系和系统级相互作用描述）是持久的，从而限制了该网络适应和进化的能力。
