Search for: All records

The reactivity profile of atomic oxygen [O( 3 P)] in the condensed phase has shown a preference for the thiol group of cysteines. In this work, water-soluble O( 3 P)-precursors were synthesized by adding aromatic burdens and water-soluble sulphonic acid groups to the core structure of dibenzothiophene- S -oxide (DBTO) to study O( 3 P) reactivity in cell lysates and live cells. The photodeoxygenation of these compounds was investigated using common intermediates, which revealed that an increase in aromatic burdens to the DBTO core structure decreases the total oxidation yield due to competitive photodeoxygenation mechanisms. These derivatives were then tested in cell lysates and live cells to profile changes in cysteine reactivity using the isoTOP-ABPP chemoproteomics platform. The results from this analysis indicated that O( 3 P) significantly affects cysteine reactivity in the cell. Additionally, O( 3 P) was found to oxidize cysteines within peptide sequences with leucine and serine conserved at the sites surrounding the oxidized cysteine. O( 3 P) was also found to least likely oxidize cysteines among membrane proteins. 

Abstract We have developed a novel visible‐light‐catalyzed bioconjugation reaction, PhotoCLIC, that enables chemoselective attachment of diverse aromatic amine reagents onto a site‐specifically installed 5‐hydroxytryptophan residue (5HTP) on full‐length proteins of varied complexity. The reaction uses catalytic amounts of methylene blue and blue/red light‐emitting diodes (455/650 nm) for rapid site‐specific protein bioconjugation. Characterization of the PhotoCLIC product reveals a unique structure formed likely through a singlet oxygen‐dependent modification of 5HTP. PhotoCLIC has a wide substrate scope and its compatibility with strain‐promoted azide‐alkyne click reaction, enables site‐specific dual‐labeling of a target protein.