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. Author manuscript; available in PMC: 2020 Dec 9.
Published in final edited form as: ACS Chem Biol. 2020 Feb 17;15(3):640–645. doi: 10.1021/acschembio.9b01038

Figure 1.

Figure 1.

Chemoenzymatic Semi-Synthesis Scheme. Expressed Fragment: αS1–55 is expressed as an intein fusion, labeled with AF488 maleimide, and enzymatically phosphorylated with c-Abl kinase. Uaa Mutagenesis Fragment: αS56–140 is expressed with π incorporated by unnatural amino acid mutagenesis and labeled with AF594 azide. Triply Modified αS: The αS1–55 and αS56–140 fragments are ligated and desulfurized to give phosphorylated protein for FRET experiments. Synthetic Fragment: AF488-labeled, phosphorylated αS1–55 produced by ligation of a synthesized (1–29) or expressed (1–36) N-terminus and a synthetic central fragment (30–55 or 37–55).