Fig. 5: Secondary structure changes associated with FUS ageing.
From: Nanoscale profiling of evolving intermolecular interactions in ageing FUS condensates
a The secondary structure of FUS condensates was measured as a function of time using FTIR, at ta = 0 to 24 h. The second derivative of the amide I bands are presented for early, ta = 0, 2 and 4 h (b) and late, ta = 8 and 24 h c condensates. Differences in secondary structure components are highlighted based on characteristic absorption peaks. d The width of the amide I peak was measured, FWHM = full width at half maximum. e The relative amounts of secondary structure were quantified for early, ta = 0, 2 and 4 h (c) and late, ta = 8 and 24 h, based on the second derivative spectra. f Tyrosine residues, and their chemical environment, can be measured via FTIR. The tyrosine absorption peak for the liquid/dense phase is at ~1517 cm−1, indicated by the black dashed line. Tyrosine peaks were also recorded for ta = 2 and 4 h (green) and solid ta = 24 h and 5 d (purple) samples. A different chemical environment will result in shifts of the peak. g The second derivative of the tyrosine peak reveals downward and upward shifts for early-aged condensates (ta = 2 and 4 h, green) and late-aged condensates (ta = 24 and 120 h, purple), respectively, relative to the peak position of at ta = 0 h (black). The black dashed line indicates the peak position at ta = 0 h. h The shifts in the tyrosine peak relative to ta = 0 h were quantified. i The intensity of the tyrosine peak was measured by considering the integral of the peak. Differences in the peak intensity at ta = 24 and 120 h indicates a different chemical environment. All measurements were taken from 3 technical replicates. Error bars represent SD throughout.
