Functionalized Au15 nanoclusters as luminescent probes for protein carbonylation detection

Guillaume F Combes,Philippe Dugourd,Christophe Moulin,Pierre-François Brevet,Miroslav Radman,Romain Ladouce,Isabelle Russier-Antoine,Rodolphe Antoine,Željka Sanader Maršić,Marion Girod,Katarina Trajković,Hussein Fakhouri,Franck Bertorelle,Martina Perić Bakulić,Srestha Basu,Anita Krisko,Vlasta Bonačić-Koutecký

doi:10.1038/s42004-021-00497-z

Abstract

Atomically precise, ligand-protected gold nanoclusters (AuNCs) attract considerable attention as contrast agents in the biosensing field. However, the control of their optical properties and functionalization of surface ligands remain challenging. Here we report a strategy to tailor AuNCs for the precise detection of protein carbonylation—a causal biomarker of ageing. We produce Au15SG13 (SG for glutathione) with atomic precision and functionalize it with a thiolated aminooxy moiety to impart protein carbonyl-binding properties. Mass spectrometry and molecular modelling reveal the key structural features of Au15SG12-Aminooxy and its reactivity towards carbonyls. Finally, we demonstrate that Au15SG12-Aminooxy detects protein carbonylation in gel-based 1D electrophoresis by one- and two-photon excited fluorescence. Importantly, to our knowledge, this is the first application of an AuNC that detects a post-translational modification as a nonlinear optical probe. The significance of post-translational modifications in life sciences may open avenues for the use of Au15SG13 and other nanoclusters as contrast agents with tailored surface functionalization and optical properties.

Highlights

Precise, ligand-protected gold nanoclusters (AuNCs) attract considerable attention as contrast agents in the biosensing field
The hydrazone bond formed between the cyanine hydrazide and protein carbonyls is usually sensitive to acidic environment and narrow pH range conditions are required to optimize the efficient binding of cyanine-hydrazide fluorescent dye to its carbonyl targets
Using mass spectrometry (MS) approach, we showed that the resulting NCs bind carbonylated proteins through the formation of an oxime bond between the aminooxy-containing thiolated ligand on the NC and the carbonylated amino acid on the protein

Summary

Introduction

Precise, ligand-protected gold nanoclusters (AuNCs) attract considerable attention as contrast agents in the biosensing field. We report a strategy to tailor AuNCs for the precise detection of protein carbonylation—a causal biomarker of ageing. We produce Au15SG13 (SG for glutathione) with atomic precision and functionalize it with a thiolated aminooxy moiety to impart protein carbonyl-binding properties. We demonstrate that Au15SG12-Aminooxy detects protein carbonylation in gel-based 1D electrophoresis by one- and two-photon excited fluorescence. Ligand-protected gold nanoclusters (AuNCs) with gold kernel composed of few dozen of atoms possess moleculelike properties[15] such as luminescence[16,17]. Such AuNCs can exhibit strong photoluminescence from ultraviolet to the NIR region[18,19].

Methods

Results

Conclusion