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Amyloidogenic model peptides as catalysts for stereoselective aldol reactions

机译：Amyloidogenic模型肽作为催化剂立体选择醇醛反应

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摘要

In this work, the self-assembly in an aqueous medium of two compounds derived from amyloid-like structures, [RF](4) and P[RF](4) (where: R = arginine; F = phenylalanine; P = proline), was studied by using spectroscopy, microscopy, and scattering techniques. The peptides presented a similar critical aggregation concentration (cac) considering the same medium conditions (similar to 0.35 mmol L-1 at 25 degrees C). The stability of the systems was analyzed by zeta potential measurements, which showed that under acidic and neutral conditions the colloidal particles remained stable, and for basic solutions, strongly interacting colloids and supramolecular aggregates in solution were observed. CD data confirmed the changes in the conformation of the secondary structures for both compounds by changing the pH of the solution. By SAXS, the curves were fitted using a fractal structure factor, and we observed that the size of the monomers that compose the fractal aggregates of [RF](4) is twice as large as that of P[RF](4). These compounds showed potential as catalysts in aldol reactions, using cyclohexanone and p-nitrobenzaldehyde. In this case, under optimized reaction conditions, 78% conversion (ee up to 85%) was observed in [RF](4) solutions, while P[RF](4) had only 51% conversion (ee up to 85%). Our results show, for the first time, a dependence of the morphology on the stereoselective aldol reactions, whereas the folding arrangement of the chiral assemblies in the polypeptide chains plays an essential role in the access of the reactants to the active surface sites.
机译：在这部作品中,自组装水两种化合物来自amyloid-like媒介结构,(RF)(4)和P (RF)(4)(地点:R =精氨酸;研究利用光谱学、显微镜和散射技术。类似的临界聚集浓度(cac)考虑到相同的介质条件(类似0.35更易与l - 1在25摄氏度)。稳定系统的分析了电动电势表明,在酸性和测量中性条件下胶体粒子保持稳定,基本解决方案,强相互作用的胶体和超分子聚合物在溶液中被观察到。证实了构象的变化二级结构的化合物改变溶液的pH值。曲线上使用一个分形结构因素,我们观察到的大小单体组成的分形聚集(射频)(4)是两倍的P (RF)(4)。这些化合物显示潜在的催化剂使用环己酮和醇醛反应,p-nitrobenzaldehyde。优化反应条件,78%转换(ee85%)在(RF)(4)的解决方案,而P (RF)(4)只有51%的转换(ee85%)。依赖的形态立体选择醇醛反应,而折叠手性组装的安排多肽链中扮演着重要的角色访问反应物的活性表面网站。

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