Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-580, Santo André, Brazil.
Department of Chemistry, University of Reading, Reading RG6 6AD, United Kingdom.
Langmuir. 2020 Mar 24;36(11):2767-2774. doi: 10.1021/acs.langmuir.0c00198. Epub 2020 Mar 12.
Morphological, spectroscopic, and scattering studies of the self-assembly and aggregation of mixtures of [RF] and P[RF] peptides (where R = arginine; F = phenylalanine; P = proline), in solution and as hydrogels, were performed to obtain information about polymorphism. CD data confirmed a β-sheet secondary structure in aqueous solution, and TEM images revealed nanofibers with diameters of ∼10 nm and micrometer lengths. SAXS curves were fitted using a mass fractal-component and a long cylinder shell form factor for the liquid samples, and only a long cylinder shell form factor for the gels. Increasing the P[RF] content in the systems leads to a reduction in cylinder radius and core scattering density, suggesting an increase in packing of the peptide molecules; however, the opposite effect is observed for the gels, where the scattering density is higher in the shell for the systems containing higher P[RF] content. These compounds show potential as catalysts in the asymmetric aldol reactions, with cyclohexanone and -nitrobenzaldehyde in aqueous media. A moderate conversion (36.9%) and a good stereoselectivity (69:31) were observed for the system containing only [RF]. With increasing P[RF] content, a considerable decrease of the conversion was observed, suggesting differences in the self-assembly and packing factor. Rheological measurements were performed to determine the shear moduli for the soft gels.
对 [RF] 和 P[RF] 肽（其中 R = 精氨酸；F = 苯丙氨酸；P = 脯氨酸）混合物在溶液中和水凝胶中的自组装和聚集的形态、光谱和散射研究，以获得有关多态性的信息。CD 数据证实了水溶液中的 β-折叠二级结构，TEM 图像显示直径约为 10nm 且长度可达微米的纳米纤维。使用质量分形分量和长圆柱壳形态因子对液体样品的 SAXS 曲线进行拟合，而仅对凝胶使用长圆柱壳形态因子。在这些体系中增加 P[RF] 的含量会导致圆柱半径和核散射密度降低，表明肽分子的堆积增加；然而，对于凝胶，情况则相反，对于含有较高 P[RF]含量的体系，壳层中的散射密度更高。这些化合物在水介质中的环己酮和 -硝基苯甲醛的不对称羟醛反应中具有作为催化剂的潜力。仅含有 [RF] 的体系的转化率适中（36.9%），立体选择性好（69:31）。随着 P[RF]含量的增加，转化率明显下降，表明自组装和堆积因子存在差异。进行了流变学测量以确定软凝胶的剪切模量。
