Figure 6

FT-IR spectral analysis of DNA extracted/recovered from saliva dried and stored on filters. Saliva was dried on filters without supplements (blue lines, bars and symbols) or with 10% sucrose (orange/red lines, bars and symbols), and stored for 90 d at different temperatures (4, 22, and 37 °C). Normalized second derivative spectra of the fingerprint spectral region are presented (A,B), as well as a comparison of the band intensity ratios of the asymmetric versus symmetric PO2- stretching vibration [C; I(v1240)/I(v1080)]. Furthermore, the 1400 − 900 cm⁻¹ spectral region was subjected to PCA and score plots of the first two principal components were prepared (D; with lighter colors for higher temperatures). Pooled saliva was used from three different donors. Measurements were performed in triplicate, and mean values ± standard deviations are presented.