Extended Data Fig. 5: Optimization of protein labelling with 4-19F Phe.

(a) 19F-NMR spectra of 900 μM GB1 samples at 25 °C produced with varying concentrations of 4-19F Phe in the growth medium. (b) Labelling efficiency of GB1, measured by mass spectrometry (MS), as a function of 4-19F Phe concentration with and without the co-transformed plasmids pHE3-M4G or pHE3-W. (c) MS-derived labelling efficiencies for DNAJB1 (DNAJ), the proteasome α7 single-ring (proteasome) and Keap1 ΔN-term.