Identification of DNA methylation Raman signatures in WT and DNMT1−/− cells. (a) Raman spectra of (i) HCT116 WT and (ii) DNMT1−/− cells. Raman signatures that can be assigned to DNA bands are indicated by arrows. Standard deviations are indicated by the gray lines. n = 125. (b) Statistical analysis of significantly increased Raman bands, which can be assigned to DNA methylation. (c) Score plot of PC 1 and PC 4 shows a grouping tendency between WT and DNMT1−/− cells illustrated by a gray arrow. The score mean value of both groups for PC 4 differs significantly from each other. Two-tailed t-test, n = 125 (d) PC 4 Loading describes the Raman shifts that vary in WT cells compared to DNMT1−/− cells. Noticeable DNA peaks are indicated by arrows.