Fig. 4: Site-specific C-terminal functionalization of ubiquitin diselenide 27 via PDC.

Conversion of ubiquitin acyl hydrazide 26 to ubiquitin diselenide 27 and MALDI-TOF spectra of crude desalted reaction mixtures after C-terminal functionalization with A PEG₆- (28), B mPEG₁₇- (29), C Biotin-PEG₅- (30), D Arg₈-(PEG₄)₂-Ala- (31) and E H2AX- (32) under optimized PDC conditions. Reaction conversions were calculated through averaging integrations of HRMS-derived extracted ion chromatograms of the [M + 9H⁺]⁹⁺, [M + 8H⁺]⁸⁺ and [M + 7H⁺]⁷⁺ charge states and errors are reported as the standard deviation of the integration of these three ion peaks for a single experiment (see Supplementary Information); acac acetylacetone, TCEP tris-carboxyethylphosphine, DPDS diphenyl diselenide, Gnd.HCl guanidinium hydrochloride, HEPES = 4-(2-hydroxyethyl)−1-piperazineethanesulfonic acid, PTA 1,3,5-triaza-7-phosphaadamantane, MeCN acetonitrile, NaP sodium phosphate, Quant. quantitative conversion, Yield isolated yield of modified protein following reverse-phase HPLC purification. Created with BioRender.com.