Fig. 6: 1D ¹⁵N ssNMR analysis, schematic model of alanines conformations, and localization of β-sheet aggregates within the coacervate matrix.

a 1D ¹⁵N DE MAS ssNMR spectra on the sample with low (bottom; red) and high salt concentration (top; blue). In both spectra, the integrated peak areas suggest an average length of 4 alanines per peptide. b Schematic model of the GPB_L/pAA coacervate (left) and alanines conformation models (right). According to the ssNMR, ~60% of oligoalanines form β-sheet structure, and 23% of oligoalanine form an α-helix structure. We propose that the secondary structure is partly determined by (variations) in peptide length (n), as indicated, with hydrogen bonding within an α-helix requiring more than five residues. The point where peptides are attached to the polymer chain is indicated by a black anchor symbol. ThT binding assay on c P-GPB/pAA, d HP + NG-Ala/pAA, and e GPB/pAA coacervates. All coacervates were prepared at 0.1 M NaCl and pH 7, in presence of 0.5 mM ThT. At least five micrographs were recorded for each sample. The images shown are representative of the complete set, and the insets are histograms showing the fluorescence intensity distribution of the pixels from all images. From the histograms, it can be observed that the coacervates of P-GPB/pAA show a unimodal distribution (corresponding to the relatively homogeneous background), while the coacervates of HP + NG-Ala/pAA and GPB/pAA show a second peak or shoulder at higher fluorescence intensity values. All scale bars are 100 µm.