Protein bioconjugations appending various artificial functions are useful tools to advance interdisciplinary chemical/biological areas. In recent years, bioconjugation targeting low-reactive amino acids (Trp, Tyr, Met, His, etc.) has been widely studied inspired by synthetic chemistry researches, to pursue improved homogeneity and expanded chemical space of the bioconjugates. Tyrosine (Tyr) is an proteinogenic amino acid with a moderate abundance in the primary sequence and a moderate surface exposure. Tyr also behaves as a site of various posttranslational modifications and a hotspot for protein-protein interactions. Artificial modulation of Tyr can greatly affect such biology-related chemical process. Various researchers have reported Tyr-selective protein bioconjugations, which demanded, however, heavy metal reagents, non-biocompatible conditions, and cross-reactivity with other amino acids, greatly hampering their practical applications.<br/>Here we present a novel Tyr-bioconjugation using water-soluble iminoxyl radicals. The retro-bioconjugation also proceeded in response to external stimuli (light and/or reductant), recovering the native Tyr structure in a traceless manner. The stability and reversibility of the bioconjugates could be controlled by modifying the reagent structure. We are now exploring this unique traceless reversibility for biochemically/medicinally attractive applications.

Tyrosine-selective bioconjugation using iminoxyl radicals

ACS Spring Meeting 2021

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