Fig. 5
Statistical analysis. The boxplots present spectroscopic ratios derived from control, plaque, and core spectra. The red bar indicates the median value, the blue boxes range between the first and third quartile. The black whiskers extend the extremes of the distribution, excluding outliers (black crosses). The significance bars announce the confidence levels. A Ratios between the Amide II band and the CH stretching bands, indicating protein accumulation. B Ratios between the Amide I band of β-sheets and non-β-sheet structures, indicating β-sheet levels. C The scatterplot illustrates the correlation between protein and β-sheet levels in plaques. A successive accumulation of β-sheet protein alongside the plaque development sequence is apparent. D The negative height difference of the bands around 1628 and 1693 cm−1 in 2nd derivative spectra, indicating increased proportions of parallel β-sheets