(a–d) Representative fits of the
IR spectra for [1-13C]F19 Aβ(16–22) incubated
at (a–c) neutral
pH for (a) 1 h, (b) 5 days, and (c) 14 days and (d) at acidic pH for
7 days. Linear combinations of spectra corresponding to mature assemblies
with parallel (black), in-register antiparallel (red), and out-of-register
antiparallel (green) β-sheets and unassembled peptide (blue)
are presented as well as the resulting sums (orange lines), which
are compared to the experimental spectra (orange squares). (e, f)
IR spectral coefficients derived from fits to the IR spectra of assembled
[1-13C]F19 Aβ(16–22) under (e) acidic and
(f) neutral pH assembly conditions.