Figure 3. FTIR spectra of Tau_244–372 fibrils formed in the presence and absence of Pb²⁺ at 37°C.

(A) The FTIR spectra in the amide I′ region of Tau_244–372 fibrils. (B) The second derivatives of the amide I′ bands of Tau_244–372 fibrils. 200 µM Tau_244–372 was incubated with 0–20 µM Pb²⁺ (black: 0 µM, and red: 20 µM) in 10 mM HEPES buffer (pH 7.4) containing 100 mM NaCl, 1 mM DTT, and 5 µM heparin, to produce fibrils.