Tracing overlapping biological signals in mid-infrared using colonic tissues as a model system

Figure 3 Variation of the spectra due to aperture. A: Cluster analysis of spectra obtained with apertures of 45 and 90 μm to show the variation if composition between zones and similarity within zones. Forty-five and ninety numbers indicate the apertures in the labels of crypts; B: PCA analysis of the spectra showing the variation in biochemistry along the crypt diameter. The lines are drawn to show the group and are not mathematical in origin; C: Second derivative of the normalized spectra obtained with various apertures, in the region between 900-1200 cm^-1 showing the different wave numbers where the carbohydrates and nucleic acids absorb and how these vary due to the aperture.