Mamajanov Irena, Callahan Michael P, Dworkin Jason P, Cody George D
Geophysical Laboratory, Carnegie Institution for Science, Washington, DC, 20015, USA,
Orig Life Evol Biosph. 2015 Jun;45(1-2):123-37. doi: 10.1007/s11084-015-9430-9. Epub 2015 May 20.
Proteins are responsible multiple biological functions, such as ligand binding, catalysis, and ion channeling. This functionality is enabled by proteins' three-dimensional structures that require long polypeptides. Since plausibly prebiotic synthesis of functional polypeptides has proven challenging in the laboratory, we propose that these functions may have been initially performed by alternative macromolecular constructs, namely hyperbranched polymers (HBPs), during early stages of chemical evolution. HBPs can be straightforwardly synthesized in one-pot processes, possess globular structures determined by their architecture as opposed to folding in proteins, and have documented ligand binding and catalytic properties. Our initial study focuses on glycerol-citric acid HBPs synthesized via moderate heating in the dry state. The polymerization products consisted of a mixture of isomeric structures of varying molar mass as evidenced by NMR, mass spectrometry and size-exclusion chromatography. Addition of divalent cations during polymerization resulted in increased incorporation of citric acid into the HBPs and the possible formation of cation-oligomer complexes. The chelating properties of citric acid govern the makeup of the resulting polymer, turning the polymerization system into a rudimentary smart material.
蛋白质负责多种生物学功能，如配体结合、催化和离子通道作用。这种功能是由蛋白质的三维结构实现的，而这需要长多肽链。由于在实验室中，功能性多肽的可能的益生元前体合成已被证明具有挑战性，我们提出，在化学进化的早期阶段，这些功能可能最初是由替代的大分子构建体，即超支化聚合物（HBP）执行的。HBP可以通过一锅法直接合成，具有由其结构决定的球状结构，与蛋白质的折叠不同，并且具有已记录的配体结合和催化特性。我们的初步研究集中于通过在干燥状态下适度加热合成的甘油-柠檬酸HBP。核磁共振、质谱和尺寸排阻色谱证明，聚合产物由不同摩尔质量的异构结构混合物组成。聚合过程中添加二价阳离子导致柠檬酸更多地掺入HBP，并可能形成阳离子-低聚物络合物。柠檬酸的螯合特性决定了所得聚合物的组成，使聚合系统变成一种初级智能材料。
