Extended Data Fig. 9: Upscaling of the protein modification with pySOOF and ¹⁹F NMR analysis.

The scalability of protein modification reaction with pySOOF was studied and high conversion efficiencies were observed for pySOOF-Lys, LysAc, Lys(Me)₃, Met, Glu and DfeGly using 4–6 mg of Dha-tagged histone. After the photochemical reaction, the crude mixture was vortexed with either EDTA or DTT, followed by buffer exchange to deuterated buffer (NH₄OAc, 250 mM, pH 7 in D₂O with TFA as internal standard) using desalting columns. After purification, excellent yields were determined by checking the protein concentration by absorbance at 280 nm on a micro-volume spectrophotometer. Spectra were recorded on a Bruker NMR system (AV600) and all PTMs showed characteristic peaks with unique chemical shifts.