Fig. 2.
2D IR spectra, linear IR spectra, and diagonal traces of 2D IR spectra of isotopologs of Aβ40. (A–R) 2D IR spectra in the 13C = 18O region of 18 isotopologs as indicated. The residue symbol followed by an asterisk indicates the indicated isotopologs of the Aβ40 strand. Red contours are positive signals, and blue contours are negative. All of the 2D IR spectra are real absorptive spectra, were collected at zero waiting time (i.e., T = 0), and are plots of the coherence frequency ωτ versus the detection frequency ωt. (S and T) Linear IR spectra (blue) and diagonal traces (red) of 2D IR spectra for two isotopologs (L17* and G37*).