# Azidocoumarin Glycan Probes for Photoinduced Cross-Linking and In Situ Fluorescent Labeling

## TL;DR

This paper introduces new azidocoumarin glycan probes that can cross-link and fluorescently label glycan-binding proteins when exposed to UV light.

## Contribution

The study presents a novel 7-azidocoumarin derivative for creating glycan-based photo affinity probes with fluorogenic properties.

## Key findings

- Azidocoumarin glycan probes selectively target and covalently link to lectins with turn-on fluorescence.
- The probes enable recognition of lectins in complex biological environments.
- This approach opens opportunities to identify and localize glycan receptors in cells and tissues.

## Abstract

Photoinduced affinity labeling for cross-linking biomolecules
in
close spatial proximity has become a powerful strategy in life science
studies to identify interaction partners in fundamental research as
well as biomarkers in applied studies. Next-generation photo-cross-linkers
additionally provide inducible fluorogenic properties to enable a
visual read-out. Azido-substituted coumarin is nonfluorescent, but
UV irradiation initiates the formation of a highly reactive nitrene
radical that can act as a cross-linker while restoring the fluorescence
activity of the coumarin chromophore. In this study, we present a
7-azidocoumarin derivative that is used as a suitable building block
for solid-phase synthesis and demonstrates easy access to a variety
of glycan-based photo affinity probes. Applications of photo-cross-linkers
for glycans and their respective binding proteins are still rare.
We show several azidocoumarin glycan-presenting probes and their selective
targeting and covalent linking to lectins, accompanied by a turn-on
fluorescence activity of the coumarin fluorophore. Selective recognition
of specific target lectins from the presented glycan photo affinity
probes is further demonstrated in complex biological environments,
which now open opportunities for identifying and localizing both known
and previously unidentified glycan receptors in cells, tissues, or
patient samples.