The nanoscale analysis was done taking advantage of infrared nanoscopy. To this aim, 5 μL of samples were dropped onto gold-coated then dried in vacuum. The measurements were performed at the SISSI-Bio infrared beamline of Elettra Sincrotrone Trieste taking advantage of a Neascope microscope (Attocube System AG), equipped with a scattering-type Scanning Near field Optical Microscopy (SNOM) module. Arrow type, high sensitivity, 20 nm wide and coated with PtIr (Neaspec GmbH, Munich) were exploited to collect the scattered IR signal. The microscope was operated in tapping mode with at a cantilever frequency of 232 kHz and a free amplitude of oscillation around 100 nm. The DFG (Difference Frequency Generation) laser was set to emit in the spectral region 1000-2000 cm-1, with maximum emission at 1666 cm-1. The usable spectral window allowed to access both amide and lateral chains modes.25, 34 Spectra were acquired at a resolution of 8 cm-1 with each measurement taking ~3 min. A clean gold surface was used as a reference to calculate nano-IR absorbance. Neaplot (Attocube System AG, Munich) software was used for spectroscopic data analyses and topographic imaging maps were analyzed with Gwyddion 2.59. 2nd-harmonic of optical phase signal was considered for nano-IR absorbance curves. Principal Component Analysis was performed on nano-IR absorption spectra thanks to the use of Quasar 1.7.0.35 A preprocessing procedure was applied to all spectra comprising a cut of spectra between 1720 1350 cm-1, rubber-band baseline correction, vector normalization and 15-points smoothing. Variance ellipses were built by considering 90% of the total variance for each sample.