Fig. 4.

Data obtained from a Daylight Solutions Spero microscope where the same sample as in Fig. 2 was measured, showing a the spectroscopic image of peak height at 1540 cm^-1 and b example extracted spectra from different pixels. All spectra were collected with 0.5-cm^-1 steps before application of a moving average of 8-cm^-1 width, and downsampling to 4 cm^-1, where the spectra shown in b have been normalized with respect to the amide I band