# From loops to caps: discriminating peptide binding to distinct G-quadruplex tetrads using 5-furyl-2′-deoxyuridine fluorescent probes

## TL;DR

A fluorescent probe helps track how peptides bind to specific parts of G-quadruplex structures.

## Contribution

A new method using 5FU fluorescent probes distinguishes peptide binding to specific G-quadruplex tetrads.

## Key findings

- 5FU labels at G4 caps enable fluorescence turn-on for tetrad-specific binding detection.
- The method reveals tetrad preference and binding affinities of RHAU23 peptides.
- The approach works on T95-2T and other parallel G-quadruplex structures.

## Abstract

We report the use of 5-furyl-2′-deoxyuridine (5FU) as a fluorescent probe to distinguish ligand binding to distinct G-quadruplex tetrads. Site-specific incorporation of 5FU into T95-2T at the capping regions enabled discrimination of peptide-binding events via fluorescence turn-on, providing insights into tetrad preference and binding affinities using the 5FU-G4/RHAU peptide system.

Site-specific 5-furyl-2′-deoxyuridine (5FU) labels at G-quadruplex (G4) caps generate fluorescence turn-on readouts that resolve tetrad-specific binding of peptide RHAU23, enabling tetrad affinity determination on T95-2T and other parallel G4s.