Figure 1.
Spectral characteristics of NBA/EDC-modified PLGA samples.
Far-UV CD spectra of PLGA samples modified with NBA (at fixed1∶3 Glu side chain: NBA molar ratio) in the presence of varying concentrations of EDC (expressed as molar ratio of EDC:Glu side chains: 0, 0.005, 0.015, 0.05, 0.15, 0.5, and 1.5) after alkalization to pH 8.3 (A) and subsequent acidification to pH 4.9 (B). Changes in light scattering intensity (at 350 nm) of NBA/EDC-modified PLGA formed at 1.5 EDC:Glu molar ratio caused by pH-adjustment are shown in the inset in panel (B).
Figure 2.
Infared spectra of PLGA samples right after covalent modifications with NBA at indicated EDC:Glu molar ratios (left panel), and after subsequent acidification to pD 4.3 and 13-day-long incubation at 65°C (right panel).
The data corresponds to several parallel experiments.
Figure 3.
TEM (top row) and SEM (bottom row) images of amyloid fibrils formed by unmodified PLGA (β2) and selected NBA/EDC-modified PLGA samples.
Figure 4.
Cross-section view at a model of different inter-sheet distances and packing modes of Glu side chains in the β1/β2-type structural variants of PLGA aggregates with the antiparallel arrangement of strands (A).
Red circles mark sites of three-center hydrogen bonds with bifurcated carbonyl acceptors. Random covalent modification of Glu side chains (within frames) cause local structural defects and result in less-densely-packed β1 fibrils (B).
Figure 5.
Infrared spectra of PLGA aggregates doped with PLL (black lines), or PDL (red lines) at the indicated Glu:Lys side chain molar ratios.
Aggregates were formed by incubation (72h/60°C) of acidified mixtures of PLGA and PLL (PDL). Blue spectrum corresponds to β2-fibrils formed in the absence of polylysine.