Peakfit 4

XRD diffraction patterns were obtained with an X'Pert Pro (Malvern PANalytical) automated diffractometer using Ge(111)-monochromated CuKa radiation and an X'Celerator detector. Diffractograms were recorded between 5°and 45°(2u) in 0.017°steps at 45 kV and 35 mA for 30 min. Isolated cuticle and cutin samples were placed on an aluminum support adapting them to the goniometer in a u to 2u configuration. The position and the FWHM of peaks were determined after fitting using the software PeakFit 4.11 (Systat Software). The basal spacing d, the average separation between polymer chains in the cuticles, was calculated from the rearrangement of Bragg's diffraction equation: d 5 ½ðl=sin uÞ;
where l is the wavelength of radiation (;1.54 Å) and u is the diffraction maximum angle. The FWHM parameter was calculated by difference of the basal spacings for the strong maximum at half-height intensity.

Protein oligomers were analysed using size-exclusion chromatography. Samples were loaded on a Superdex 200 Increase 10/300 (GE Healthcare, Piscataway, NJ, USA) column pre-equilibrated with carbonate buffer at 0.75 ml min -1 . Protein samples intended for small-angle X-ray scattering (SAXS) were prepared by collecting fractions corresponding to each oligomer population and concentrated to 5 mg ml -1 , using an Amicon Centrifugal Filters 3 K (Millipore, Cork, Ireland). The supernatant was centrifuged at 15 000g for 30 min to remove possible aggregates and stored at -80 °C. Protein oligomers were re-analysed under the same SEC conditions to assess the structural stability upon separation. The hydrodynamic radius (R h ) was obtained using a protein standard (GE Healthcare, Piscataway, NJ, USA), and the relative amounts of oligomeric forms were calculated by Gaussian deconvolution of the obtained size-exclusion chromatograms using the Peakfit 4.12 software (Systat Software Inc.) and applying a residual method to resolve the overlapped peaks.