Fig. 3: Nano-FTIR analysis of silk protein assemblies.
FTIR maps collected from samples containing a a mixture of protein nanocompartments and protein monomers and b silk protein nanofibrils. (i) FTIR- reflection maps collected at 1482 cm−1, to distinguish general protein content from organic contaminants (negative control); (ii) absorption maps collected at 1482 cm−1; (iii) absorption maps collected at 1600 cm−1; (iv) absorption maps collected at 1629 cm−1 showing the β-sheet content; (v) FTIR absorption maps collected at 1641 cm−1 showing a signal from a disordered random coil and an α-helix. c AFM topography image of silk monomers (marked with blue dots) and silk compartments (marked with red dots), from which IR spectra were recorded and depicted in d nano-FTIR spectra of silk protein monomers, and e nano-FTIR spectra of protein compartments. f AFM topography image depicting silk nanofibrils (marked with green dots), from which FTIR spectra were recorded and depicted in g. h Bar chart of the relative amounts of the β-sheets at 1610–1635 cm–1, the anti-parallel β-sheets at 1690–1705 cm–1, random coil and α-helixes at 1635–1665 cm–1, and β-turns at 1665–1690 cm–1 in (d), (e) and (g). Source data are provided as a Source Data file.
