摘要
In extant biology, biopolymers perform multiple crucial functions. The biopolymers are synthesized by enzyme-controlled biosystems that would not have been available at the earliest stages of chemical evolution and consist of correctly sequenced and/or linked monomers. Some of the abiotic “messy” polymers approximate some functions of biopolymers. Condensation polymers are an attractive search target for abiotic functional polymers since principal polymers of life are produced by condensation and since condensation allows for the accurate construction of high polymers. Herein the formation of hyperbranched polyesters that have been previously used in the construction of enzyme-like catalytic complexes is explored. The experimental setup compares between the branched polyesters prepared under mild continuous heating and the wet-dry cycling associated with environmental conditions, such as dew formation or tidal activities. The results reveal that periodic wetting during which partial hydrolysis of the polyester occurs, helps to control the chain growth and delays the gel transition, a mechanism contributing to the tar formation. Moreover, the NMR and mass spec analyses indicate that continuously dried samples contain higher quantities of crosslinked and macrocyclic products, whereas cycled systems are enriched in branched structures. Ostensibly, environmental conditions have the ability to exert a rudimentary pressure to selectively enrich the polyesterification products in polymers of different structures and properties. At the early stages of chemical evolution, in the absence of biological machinery, this example of environmental control could have been for selectivity in chemical systems. As expected in marginally controlled systems, the identification of each component of the heterogeneous system has proved challenging, but it is not crucial for drawing the conclusions.
摘要译文
在现存生物学中，生物聚合物进行多个重要功能。通过酶控制的生物系统合成生物聚合物，该生物系统不会在化学进化的最早阶段可用，并由正确测序和/或连接的单体组成。一些非生物“凌乱”聚合物近似有些功能的生物聚合物。缩合聚合物是非生物官能聚合物的吸引力的搜索靶标，因为通过冷凝产生的主要聚合物并因此冷凝允许准确构建高聚合物的凝结。在此，探讨了以前用于酶样催化复合物构建的超支化聚酯的形成。实验装置比较在轻度连续加热下制备的支化聚酯和与环境条件相关的湿循环，例如露珠或潮汐活性。结果表明，周期性润湿在其发生聚酯的部分水解，有助于控制链生长并延迟凝胶过渡，这是有助于焦油的机制。此外，NMR和质谱分析表明，连续干燥的样品含有较高量的交联和大环产物，而循环系统富含支链结构。表面上，环境条件具有施加基本压力的能力，以在不同结构和性能的聚合物中选择性地富集聚酯化产物。在化学进化的早期阶段，在没有生物机制的情况下，这种环境控制的例子可能是化学系统中的选择性。正如在边缘控制的系统中所预期的，异构系统的每个组分的识别已经证明了具有挑战性，但它对绘制结论并不至关重要。
Irena Mamajanov. Wet-Dry Cycling Delays the Gelation of Hyperbranched Polyesters: Implications to the Origin of Life[J]. Life, 2019,9(3): 56