Pelin JNBD et al. (2020), Amyloid Peptide Mixtures: Self-Assembly, Hydrog...

ECB-ART-48540

Langmuir 2020 Mar 24;3611:2767-2774. doi: 10.1021/acs.langmuir.0c00198.

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Amyloid Peptide Mixtures: Self-Assembly, Hydrogelation, Nematic Ordering, and Catalysts in Aldol Reactions.

Pelin JNBD , Gerbelli BB , Edwards-Gayle CJC , Aguilar AM , Castelletto V , Hamley IW , Alves WA .

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Morphological, spectroscopic, and scattering studies of the self-assembly and aggregation of mixtures of [RF]4 and P[RF]4 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]4 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]4 content. These compounds show potential as catalysts in the asymmetric aldol reactions, with cyclohexanone and p-nitrobenzaldehyde in aqueous media. A moderate conversion (36.9%) and a good stereoselectivity (69:31) were observed for the system containing only [RF]4. With increasing P[RF]4 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.

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Genes referenced: pelp1

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References [+] :

Adler-Abramovich, Phenylalanine assembly into toxic fibrils suggests amyloid etiology in phenylketonuria. 2012, Pubmed

	Figure 1. [RF]4 and P[RF]4 molecular structures.
	Figure 2. Spectroscopic characterization of P[RF]4:[RF]4 mixtures 0:1 (1), 3:7 (2); 5:5 (3), 7:3 (4), and 1:0 (5), above the cac in water, using (a) FTIR and (b) CD.
	Figure 3. XRD results obtained of P[RF]4:[RF]4 mixtures 0:1 (1), 3:7 (2); 5:5 (3), 7:3 (4), and 1:0 (5), at native pH.
	Figure 4. Schematic representation of the orthorhombic unit cell, considering the dimensions obtained by fiber XRD for [RF]4.
	Figure 5. TEM images of 0.5 wt % peptide aqueous solutions. (a) 1, (b) 2, (c) 3, (d) 4, and (e) 5, at native pH. (f) SAXS data (gray points) of peptide solutions above the cac and at native pH. Model fits (red line) using the model described in the text and fitting excluding data (green line), characteristic of the structure factor.
	Figure 6. (a) Images of the hydrogels formed by 3 wt% peptide samples, as indicated. (b) Storage and shear modulus obtained by rheology experiments in frequency sweep mode, using σ = 3 Pa for 1, 1 Pa for 3, and 5 Pa for 5.
	Figure 7. (a) SAXS data (gray) and fitted curves (red) using a long cylinder shell form factor model, for 3 wt % hydrogels of 1, 3, and 5. (b) Images of the birefringence between crossed polarizers for 3 wt % hydrogels of 1, 3, and 5.