Targeting Tryptophan for Tagging through Photoinduced Electron Transfer

The chemical modification of tryptophan (Trp) has been the subject of interest for nearly 100 years, yet the development of modification conditions that exploit the inherent photolability of Trp has remained elusive. With this perspective, we discuss our recently reported method for Trp photobioconjugation that uses N -carbamoyl pyridinium salts to engage Trp in photoinduced electron transfer. We detail our inspiration and rationale, and we place our report in the context of selected prior art in the field. 1 Introduction 2 Light Activation as a Design Principle in Bioconjugation 3 Targeting Tryptophan with Light 4 Reaction Design and Proof of Concept 5 Mechanistic Considerations 6 Establishing Mechanistic Control 7 Conclusions and Outlook.