Figure 2.

(A) ¹⁹F NMR spectrum of 5-FTrpPA (230 μM). This spectrum represents 12000 transients in 50 mM Tris/25 mM Mes/25 mM AcOH buffer (pH 8.0) with 10% D₂O. Data were referenced to an internal standard of 0.02 mM pF-Phe and processed with 10 Hz line broadening. (B) Urea denaturation of 5-FTrpPA as measured using ¹⁹F NMR. Each spectrum represents 7000 transients recorded at 20 °C at 300 μM in 50 mM Tris/25 mM Mes/25 mM AcOH (pH 8.0) with 10% D₂O. (C) Comparison of ¹⁹F NMR spectra of 5-FTrp PA₂₀ to that of full-length PA (PA₈₃) at 3.2 M urea. The PA₂₀ spectrum was recorded at 150 μM and represents 16000 transients recorded at 20 °C. Note that the resonances in PA₈₃ at −43.5, −46, and −46.8 ppm are at positions identical to those of PA₂₀. Data were referenced to an internal standard of 0.02 mM pF-Phe.