Peptide spectra were processed with OMNIC 7.3 SP1 software (Thermo Scientific). A D2O spectrum recorded using the same path length spacer as for the sample was subtracted from the sample spectrum. Subtracted spectra were then baseline corrected with a manually selected baseline, whose points were fixed to spectral values and interpolated using a spline function. To fit the amide I′ band (in the 1720-1580 cm -1 range), baseline corrected spectra were processed with the OMNIC Peak Analysis tool . Gaussian-Lorentzian peak functions were fitted and optimised. Once converged, these peaks were recorded as the relative areas of each peak and associated to a specific secondary structure or amino acid residue .